| <title>Changes</title> |
| |
| <para>The following chapters document the evolution of the V4L2 API, |
| errata or extensions. They are also intended to help application and |
| driver writers to port or update their code.</para> |
| |
| <section id="diff-v4l"> |
| <title>Differences between V4L and V4L2</title> |
| |
| <para>The Video For Linux API was first introduced in Linux 2.1 to |
| unify and replace various TV and radio device related interfaces, |
| developed independently by driver writers in prior years. Starting |
| with Linux 2.5 the much improved V4L2 API replaces the V4L API, |
| although existing drivers will continue to support V4L applications in |
| the future, either directly or through the V4L2 compatibility layer in |
| the <filename>videodev</filename> kernel module translating ioctls on |
| the fly. For a transition period not all drivers will support the V4L2 |
| API.</para> |
| |
| <section> |
| <title>Opening and Closing Devices</title> |
| |
| <para>For compatibility reasons the character device file names |
| recommended for V4L2 video capture, overlay, radio, teletext and raw |
| vbi capture devices did not change from those used by V4L. They are |
| listed in <xref linkend="devices" /> and below in <xref |
| linkend="v4l-dev" />.</para> |
| |
| <para>The V4L <filename>videodev</filename> module automatically |
| assigns minor numbers to drivers in load order, depending on the |
| registered device type. We recommend that V4L2 drivers by default |
| register devices with the same numbers, but the system administrator |
| can assign arbitrary minor numbers using driver module options. The |
| major device number remains 81.</para> |
| |
| <table id="v4l-dev"> |
| <title>V4L Device Types, Names and Numbers</title> |
| <tgroup cols="3"> |
| <thead> |
| <row> |
| <entry>Device Type</entry> |
| <entry>File Name</entry> |
| <entry>Minor Numbers</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry>Video capture and overlay</entry> |
| <entry><para><filename>/dev/video</filename> and |
| <filename>/dev/bttv0</filename><footnote> <para>According to |
| Documentation/devices.txt these should be symbolic links to |
| <filename>/dev/video0</filename>. Note the original bttv interface is |
| not compatible with V4L or V4L2.</para> </footnote>, |
| <filename>/dev/video0</filename> to |
| <filename>/dev/video63</filename></para></entry> |
| <entry>0-63</entry> |
| </row> |
| <row> |
| <entry>Radio receiver</entry> |
| <entry><para><filename>/dev/radio</filename><footnote> |
| <para>According to |
| <filename>Documentation/devices.txt</filename> a symbolic link to |
| <filename>/dev/radio0</filename>.</para> |
| </footnote>, <filename>/dev/radio0</filename> to |
| <filename>/dev/radio63</filename></para></entry> |
| <entry>64-127</entry> |
| </row> |
| <row> |
| <entry>Teletext decoder</entry> |
| <entry><para><filename>/dev/vtx</filename>, |
| <filename>/dev/vtx0</filename> to |
| <filename>/dev/vtx31</filename></para></entry> |
| <entry>192-223</entry> |
| </row> |
| <row> |
| <entry>Raw VBI capture</entry> |
| <entry><para><filename>/dev/vbi</filename>, |
| <filename>/dev/vbi0</filename> to |
| <filename>/dev/vbi31</filename></para></entry> |
| <entry>224-255</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </table> |
| |
| <para>V4L prohibits (or used to prohibit) multiple opens of a |
| device file. V4L2 drivers <emphasis>may</emphasis> support multiple |
| opens, see <xref linkend="open" /> for details and consequences.</para> |
| |
| <para>V4L drivers respond to V4L2 ioctls with an &EINVAL;. The |
| compatibility layer in the V4L2 <filename>videodev</filename> module |
| can translate V4L ioctl requests to their V4L2 counterpart, however a |
| V4L2 driver usually needs more preparation to become fully V4L |
| compatible. This is covered in more detail in <xref |
| linkend="driver" />.</para> |
| </section> |
| |
| <section> |
| <title>Querying Capabilities</title> |
| |
| <para>The V4L <constant>VIDIOCGCAP</constant> ioctl is |
| equivalent to V4L2's &VIDIOC-QUERYCAP;.</para> |
| |
| <para>The <structfield>name</structfield> field in struct |
| <structname>video_capability</structname> became |
| <structfield>card</structfield> in &v4l2-capability;, |
| <structfield>type</structfield> was replaced by |
| <structfield>capabilities</structfield>. Note V4L2 does not |
| distinguish between device types like this, better think of basic |
| video input, video output and radio devices supporting a set of |
| related functions like video capturing, video overlay and VBI |
| capturing. See <xref linkend="open" /> for an |
| introduction.<informaltable> |
| <tgroup cols="3"> |
| <thead> |
| <row> |
| <entry>struct |
| <structname>video_capability</structname> |
| <structfield>type</structfield></entry> |
| <entry>&v4l2-capability; |
| <structfield>capabilities</structfield> flags</entry> |
| <entry>Purpose</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><constant>VID_TYPE_CAPTURE</constant></entry> |
| <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry> |
| <entry>The <link linkend="capture">video |
| capture</link> interface is supported.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_TUNER</constant></entry> |
| <entry><constant>V4L2_CAP_TUNER</constant></entry> |
| <entry>The device has a <link linkend="tuner">tuner or |
| modulator</link>.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_TELETEXT</constant></entry> |
| <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry> |
| <entry>The <link linkend="raw-vbi">raw VBI |
| capture</link> interface is supported.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_OVERLAY</constant></entry> |
| <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry> |
| <entry>The <link linkend="overlay">video |
| overlay</link> interface is supported.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_CHROMAKEY</constant></entry> |
| <entry><constant>V4L2_FBUF_CAP_CHROMAKEY</constant> in |
| field <structfield>capability</structfield> of |
| &v4l2-framebuffer;</entry> |
| <entry>Whether chromakey overlay is supported. For |
| more information on overlay see |
| <xref linkend="overlay" />.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_CLIPPING</constant></entry> |
| <entry><constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant> |
| and <constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant> in field |
| <structfield>capability</structfield> of &v4l2-framebuffer;</entry> |
| <entry>Whether clipping the overlaid image is |
| supported, see <xref linkend="overlay" />.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_FRAMERAM</constant></entry> |
| <entry><constant>V4L2_FBUF_CAP_EXTERNOVERLAY</constant> |
| <emphasis>not set</emphasis> in field |
| <structfield>capability</structfield> of &v4l2-framebuffer;</entry> |
| <entry>Whether overlay overwrites frame buffer memory, |
| see <xref linkend="overlay" />.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_SCALES</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>This flag indicates if the hardware can scale |
| images. The V4L2 API implies the scale factor by setting the cropping |
| dimensions and image size with the &VIDIOC-S-CROP; and &VIDIOC-S-FMT; |
| ioctl, respectively. The driver returns the closest sizes possible. |
| For more information on cropping and scaling see <xref |
| linkend="crop" />.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_MONOCHROME</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>Applications can enumerate the supported image |
| formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device |
| supports grey scale capturing only. For more information on image |
| formats see <xref linkend="pixfmt" />.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_SUBCAPTURE</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>Applications can call the &VIDIOC-G-CROP; ioctl |
| to determine if the device supports capturing a subsection of the full |
| picture ("cropping" in V4L2). If not, the ioctl returns the &EINVAL;. |
| For more information on cropping and scaling see <xref |
| linkend="crop" />.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_MPEG_DECODER</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>Applications can enumerate the supported image |
| formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device |
| supports MPEG streams.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_MPEG_ENCODER</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>See above.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_MJPEG_DECODER</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>See above.</entry> |
| </row> |
| <row> |
| <entry><constant>VID_TYPE_MJPEG_ENCODER</constant></entry> |
| <entry><constant>-</constant></entry> |
| <entry>See above.</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>The <structfield>audios</structfield> field was replaced |
| by <structfield>capabilities</structfield> flag |
| <constant>V4L2_CAP_AUDIO</constant>, indicating |
| <emphasis>if</emphasis> the device has any audio inputs or outputs. To |
| determine their number applications can enumerate audio inputs with |
| the &VIDIOC-G-AUDIO; ioctl. The audio ioctls are described in <xref |
| linkend="audio" />.</para> |
| |
| <para>The <structfield>maxwidth</structfield>, |
| <structfield>maxheight</structfield>, |
| <structfield>minwidth</structfield> and |
| <structfield>minheight</structfield> fields were removed. Calling the |
| &VIDIOC-S-FMT; or &VIDIOC-TRY-FMT; ioctl with the desired dimensions |
| returns the closest size possible, taking into account the current |
| video standard, cropping and scaling limitations.</para> |
| </section> |
| |
| <section> |
| <title>Video Sources</title> |
| |
| <para>V4L provides the <constant>VIDIOCGCHAN</constant> and |
| <constant>VIDIOCSCHAN</constant> ioctl using struct |
| <structname>video_channel</structname> to enumerate |
| the video inputs of a V4L device. The equivalent V4L2 ioctls |
| are &VIDIOC-ENUMINPUT;, &VIDIOC-G-INPUT; and &VIDIOC-S-INPUT; |
| using &v4l2-input; as discussed in <xref linkend="video" />.</para> |
| |
| <para>The <structfield>channel</structfield> field counting |
| inputs was renamed to <structfield>index</structfield>, the video |
| input types were renamed as follows: <informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>struct <structname>video_channel</structname> |
| <structfield>type</structfield></entry> |
| <entry>&v4l2-input; |
| <structfield>type</structfield></entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><constant>VIDEO_TYPE_TV</constant></entry> |
| <entry><constant>V4L2_INPUT_TYPE_TUNER</constant></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_TYPE_CAMERA</constant></entry> |
| <entry><constant>V4L2_INPUT_TYPE_CAMERA</constant></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>Unlike the <structfield>tuners</structfield> field |
| expressing the number of tuners of this input, V4L2 assumes each video |
| input is connected to at most one tuner. However a tuner can have more |
| than one input, &ie; RF connectors, and a device can have multiple |
| tuners. The index number of the tuner associated with the input, if |
| any, is stored in field <structfield>tuner</structfield> of |
| &v4l2-input;. Enumeration of tuners is discussed in <xref |
| linkend="tuner" />.</para> |
| |
| <para>The redundant <constant>VIDEO_VC_TUNER</constant> flag was |
| dropped. Video inputs associated with a tuner are of type |
| <constant>V4L2_INPUT_TYPE_TUNER</constant>. The |
| <constant>VIDEO_VC_AUDIO</constant> flag was replaced by the |
| <structfield>audioset</structfield> field. V4L2 considers devices with |
| up to 32 audio inputs. Each set bit in the |
| <structfield>audioset</structfield> field represents one audio input |
| this video input combines with. For information about audio inputs and |
| how to switch between them see <xref linkend="audio" />.</para> |
| |
| <para>The <structfield>norm</structfield> field describing the |
| supported video standards was replaced by |
| <structfield>std</structfield>. The V4L specification mentions a flag |
| <constant>VIDEO_VC_NORM</constant> indicating whether the standard can |
| be changed. This flag was a later addition together with the |
| <structfield>norm</structfield> field and has been removed in the |
| meantime. V4L2 has a similar, albeit more comprehensive approach |
| to video standards, see <xref linkend="standard" /> for more |
| information.</para> |
| </section> |
| |
| <section> |
| <title>Tuning</title> |
| |
| <para>The V4L <constant>VIDIOCGTUNER</constant> and |
| <constant>VIDIOCSTUNER</constant> ioctl and struct |
| <structname>video_tuner</structname> can be used to enumerate the |
| tuners of a V4L TV or radio device. The equivalent V4L2 ioctls are |
| &VIDIOC-G-TUNER; and &VIDIOC-S-TUNER; using &v4l2-tuner;. Tuners are |
| covered in <xref linkend="tuner" />.</para> |
| |
| <para>The <structfield>tuner</structfield> field counting tuners |
| was renamed to <structfield>index</structfield>. The fields |
| <structfield>name</structfield>, <structfield>rangelow</structfield> |
| and <structfield>rangehigh</structfield> remained unchanged.</para> |
| |
| <para>The <constant>VIDEO_TUNER_PAL</constant>, |
| <constant>VIDEO_TUNER_NTSC</constant> and |
| <constant>VIDEO_TUNER_SECAM</constant> flags indicating the supported |
| video standards were dropped. This information is now contained in the |
| associated &v4l2-input;. No replacement exists for the |
| <constant>VIDEO_TUNER_NORM</constant> flag indicating whether the |
| video standard can be switched. The <structfield>mode</structfield> |
| field to select a different video standard was replaced by a whole new |
| set of ioctls and structures described in <xref linkend="standard" />. |
| Due to its ubiquity it should be mentioned the BTTV driver supports |
| several standards in addition to the regular |
| <constant>VIDEO_MODE_PAL</constant> (0), |
| <constant>VIDEO_MODE_NTSC</constant>, |
| <constant>VIDEO_MODE_SECAM</constant> and |
| <constant>VIDEO_MODE_AUTO</constant> (3). Namely N/PAL Argentina, |
| M/PAL, N/PAL, and NTSC Japan with numbers 3-6 (sic).</para> |
| |
| <para>The <constant>VIDEO_TUNER_STEREO_ON</constant> flag |
| indicating stereo reception became |
| <constant>V4L2_TUNER_SUB_STEREO</constant> in field |
| <structfield>rxsubchans</structfield>. This field also permits the |
| detection of monaural and bilingual audio, see the definition of |
| &v4l2-tuner; for details. Presently no replacement exists for the |
| <constant>VIDEO_TUNER_RDS_ON</constant> and |
| <constant>VIDEO_TUNER_MBS_ON</constant> flags.</para> |
| |
| <para> The <constant>VIDEO_TUNER_LOW</constant> flag was renamed |
| to <constant>V4L2_TUNER_CAP_LOW</constant> in the &v4l2-tuner; |
| <structfield>capability</structfield> field.</para> |
| |
| <para>The <constant>VIDIOCGFREQ</constant> and |
| <constant>VIDIOCSFREQ</constant> ioctl to change the tuner frequency |
| where renamed to &VIDIOC-G-FREQUENCY; and &VIDIOC-S-FREQUENCY;. They |
| take a pointer to a &v4l2-frequency; instead of an unsigned long |
| integer.</para> |
| </section> |
| |
| <section id="v4l-image-properties"> |
| <title>Image Properties</title> |
| |
| <para>V4L2 has no equivalent of the |
| <constant>VIDIOCGPICT</constant> and <constant>VIDIOCSPICT</constant> |
| ioctl and struct <structname>video_picture</structname>. The following |
| fields where replaced by V4L2 controls accessible with the |
| &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls:<informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>struct <structname>video_picture</structname></entry> |
| <entry>V4L2 Control ID</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><structfield>brightness</structfield></entry> |
| <entry><constant>V4L2_CID_BRIGHTNESS</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>hue</structfield></entry> |
| <entry><constant>V4L2_CID_HUE</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>colour</structfield></entry> |
| <entry><constant>V4L2_CID_SATURATION</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>contrast</structfield></entry> |
| <entry><constant>V4L2_CID_CONTRAST</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>whiteness</structfield></entry> |
| <entry><constant>V4L2_CID_WHITENESS</constant></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>The V4L picture controls are assumed to range from 0 to |
| 65535 with no particular reset value. The V4L2 API permits arbitrary |
| limits and defaults which can be queried with the &VIDIOC-QUERYCTRL; |
| ioctl. For general information about controls see <xref |
| linkend="control" />.</para> |
| |
| <para>The <structfield>depth</structfield> (average number of |
| bits per pixel) of a video image is implied by the selected image |
| format. V4L2 does not explicitely provide such information assuming |
| applications recognizing the format are aware of the image depth and |
| others need not know. The <structfield>palette</structfield> field |
| moved into the &v4l2-pix-format;:<informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>struct <structname>video_picture</structname> |
| <structfield>palette</structfield></entry> |
| <entry>&v4l2-pix-format; |
| <structfield>pixfmt</structfield></entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><constant>VIDEO_PALETTE_GREY</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-GREY"><constant>V4L2_PIX_FMT_GREY</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_HI240</constant></entry> |
| <entry><para><link |
| linkend="pixfmt-reserved"><constant>V4L2_PIX_FMT_HI240</constant></link><footnote> |
| <para>This is a custom format used by the BTTV |
| driver, not one of the V4L2 standard formats.</para> |
| </footnote></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_RGB565</constant></entry> |
| <entry><para><link |
| linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB565</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_RGB555</constant></entry> |
| <entry><para><link |
| linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB555</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_RGB24</constant></entry> |
| <entry><para><link |
| linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR24</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_RGB32</constant></entry> |
| <entry><para><link |
| linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR32</constant></link><footnote> |
| <para>Presumably all V4L RGB formats are |
| little-endian, although some drivers might interpret them according to machine endianess. V4L2 defines little-endian, big-endian and red/blue |
| swapped variants. For details see <xref linkend="pixfmt-rgb" />.</para> |
| </footnote></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV422</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><para><constant>VIDEO_PALETTE_YUYV</constant><footnote> |
| <para><constant>VIDEO_PALETTE_YUV422</constant> |
| and <constant>VIDEO_PALETTE_YUYV</constant> are the same formats. Some |
| V4L drivers respond to one, some to the other.</para> |
| </footnote></para></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_UYVY</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-UYVY"><constant>V4L2_PIX_FMT_UYVY</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV420</constant></entry> |
| <entry>None</entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV411</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-Y41P"><constant>V4L2_PIX_FMT_Y41P</constant></link><footnote> |
| <para>Not to be confused with |
| <constant>V4L2_PIX_FMT_YUV411P</constant>, which is a planar |
| format.</para> </footnote></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_RAW</constant></entry> |
| <entry><para>None<footnote> <para>V4L explains this |
| as: "RAW capture (BT848)"</para> </footnote></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV422P</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-YUV422P"><constant>V4L2_PIX_FMT_YUV422P</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV411P</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-YUV411P"><constant>V4L2_PIX_FMT_YUV411P</constant></link><footnote> |
| <para>Not to be confused with |
| <constant>V4L2_PIX_FMT_Y41P</constant>, which is a packed |
| format.</para> </footnote></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV420P</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></link></para></entry> |
| </row> |
| <row> |
| <entry><constant>VIDEO_PALETTE_YUV410P</constant></entry> |
| <entry><para><link |
| linkend="V4L2-PIX-FMT-YVU410"><constant>V4L2_PIX_FMT_YVU410</constant></link></para></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>V4L2 image formats are defined in <xref |
| linkend="pixfmt" />. The image format can be selected with the |
| &VIDIOC-S-FMT; ioctl.</para> |
| </section> |
| |
| <section> |
| <title>Audio</title> |
| |
| <para>The <constant>VIDIOCGAUDIO</constant> and |
| <constant>VIDIOCSAUDIO</constant> ioctl and struct |
| <structname>video_audio</structname> are used to enumerate the |
| audio inputs of a V4L device. The equivalent V4L2 ioctls are |
| &VIDIOC-G-AUDIO; and &VIDIOC-S-AUDIO; using &v4l2-audio; as |
| discussed in <xref linkend="audio" />.</para> |
| |
| <para>The <structfield>audio</structfield> "channel number" |
| field counting audio inputs was renamed to |
| <structfield>index</structfield>.</para> |
| |
| <para>On <constant>VIDIOCSAUDIO</constant> the |
| <structfield>mode</structfield> field selects <emphasis>one</emphasis> |
| of the <constant>VIDEO_SOUND_MONO</constant>, |
| <constant>VIDEO_SOUND_STEREO</constant>, |
| <constant>VIDEO_SOUND_LANG1</constant> or |
| <constant>VIDEO_SOUND_LANG2</constant> audio demodulation modes. When |
| the current audio standard is BTSC |
| <constant>VIDEO_SOUND_LANG2</constant> refers to SAP and |
| <constant>VIDEO_SOUND_LANG1</constant> is meaningless. Also |
| undocumented in the V4L specification, there is no way to query the |
| selected mode. On <constant>VIDIOCGAUDIO</constant> the driver returns |
| the <emphasis>actually received</emphasis> audio programmes in this |
| field. In the V4L2 API this information is stored in the &v4l2-tuner; |
| <structfield>rxsubchans</structfield> and |
| <structfield>audmode</structfield> fields, respectively. See <xref |
| linkend="tuner" /> for more information on tuners. Related to audio |
| modes &v4l2-audio; also reports if this is a mono or stereo |
| input, regardless if the source is a tuner.</para> |
| |
| <para>The following fields where replaced by V4L2 controls |
| accessible with the &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and |
| &VIDIOC-S-CTRL; ioctls:<informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>struct |
| <structname>video_audio</structname></entry> |
| <entry>V4L2 Control ID</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><structfield>volume</structfield></entry> |
| <entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>bass</structfield></entry> |
| <entry><constant>V4L2_CID_AUDIO_BASS</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>treble</structfield></entry> |
| <entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry> |
| </row> |
| <row> |
| <entry><structfield>balance</structfield></entry> |
| <entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>To determine which of these controls are supported by a |
| driver V4L provides the <structfield>flags</structfield> |
| <constant>VIDEO_AUDIO_VOLUME</constant>, |
| <constant>VIDEO_AUDIO_BASS</constant>, |
| <constant>VIDEO_AUDIO_TREBLE</constant> and |
| <constant>VIDEO_AUDIO_BALANCE</constant>. In the V4L2 API the |
| &VIDIOC-QUERYCTRL; ioctl reports if the respective control is |
| supported. Accordingly the <constant>VIDEO_AUDIO_MUTABLE</constant> |
| and <constant>VIDEO_AUDIO_MUTE</constant> flags where replaced by the |
| boolean <constant>V4L2_CID_AUDIO_MUTE</constant> control.</para> |
| |
| <para>All V4L2 controls have a <structfield>step</structfield> |
| attribute replacing the struct <structname>video_audio</structname> |
| <structfield>step</structfield> field. The V4L audio controls are |
| assumed to range from 0 to 65535 with no particular reset value. The |
| V4L2 API permits arbitrary limits and defaults which can be queried |
| with the &VIDIOC-QUERYCTRL; ioctl. For general information about |
| controls see <xref linkend="control" />.</para> |
| </section> |
| |
| <section> |
| <title>Frame Buffer Overlay</title> |
| |
| <para>The V4L2 ioctls equivalent to |
| <constant>VIDIOCGFBUF</constant> and <constant>VIDIOCSFBUF</constant> |
| are &VIDIOC-G-FBUF; and &VIDIOC-S-FBUF;. The |
| <structfield>base</structfield> field of struct |
| <structname>video_buffer</structname> remained unchanged, except V4L2 |
| defines a flag to indicate non-destructive overlays instead of a |
| <constant>NULL</constant> pointer. All other fields moved into the |
| &v4l2-pix-format; <structfield>fmt</structfield> substructure of |
| &v4l2-framebuffer;. The <structfield>depth</structfield> field was |
| replaced by <structfield>pixelformat</structfield>. See <xref |
| linkend="pixfmt-rgb" /> for a list of RGB formats and their |
| respective color depths.</para> |
| |
| <para>Instead of the special ioctls |
| <constant>VIDIOCGWIN</constant> and <constant>VIDIOCSWIN</constant> |
| V4L2 uses the general-purpose data format negotiation ioctls |
| &VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a |
| &v4l2-format; as argument. Here the <structfield>win</structfield> |
| member of the <structfield>fmt</structfield> union is used, a |
| &v4l2-window;.</para> |
| |
| <para>The <structfield>x</structfield>, |
| <structfield>y</structfield>, <structfield>width</structfield> and |
| <structfield>height</structfield> fields of struct |
| <structname>video_window</structname> moved into &v4l2-rect; |
| substructure <structfield>w</structfield> of struct |
| <structname>v4l2_window</structname>. The |
| <structfield>chromakey</structfield>, |
| <structfield>clips</structfield>, and |
| <structfield>clipcount</structfield> fields remained unchanged. Struct |
| <structname>video_clip</structname> was renamed to &v4l2-clip;, also |
| containing a struct <structname>v4l2_rect</structname>, but the |
| semantics are still the same.</para> |
| |
| <para>The <constant>VIDEO_WINDOW_INTERLACE</constant> flag was |
| dropped. Instead applications must set the |
| <structfield>field</structfield> field to |
| <constant>V4L2_FIELD_ANY</constant> or |
| <constant>V4L2_FIELD_INTERLACED</constant>. The |
| <constant>VIDEO_WINDOW_CHROMAKEY</constant> flag moved into |
| &v4l2-framebuffer;, under the new name |
| <constant>V4L2_FBUF_FLAG_CHROMAKEY</constant>.</para> |
| |
| <para>In V4L, storing a bitmap pointer in |
| <structfield>clips</structfield> and setting |
| <structfield>clipcount</structfield> to |
| <constant>VIDEO_CLIP_BITMAP</constant> (-1) requests bitmap |
| clipping, using a fixed size bitmap of 1024 × 625 bits. Struct |
| <structname>v4l2_window</structname> has a separate |
| <structfield>bitmap</structfield> pointer field for this purpose and |
| the bitmap size is determined by <structfield>w.width</structfield> and |
| <structfield>w.height</structfield>.</para> |
| |
| <para>The <constant>VIDIOCCAPTURE</constant> ioctl to enable or |
| disable overlay was renamed to &VIDIOC-OVERLAY;.</para> |
| </section> |
| |
| <section> |
| <title>Cropping</title> |
| |
| <para>To capture only a subsection of the full picture V4L |
| defines the <constant>VIDIOCGCAPTURE</constant> and |
| <constant>VIDIOCSCAPTURE</constant> ioctls using struct |
| <structname>video_capture</structname>. The equivalent V4L2 ioctls are |
| &VIDIOC-G-CROP; and &VIDIOC-S-CROP; using &v4l2-crop;, and the related |
| &VIDIOC-CROPCAP; ioctl. This is a rather complex matter, see |
| <xref linkend="crop" /> for details.</para> |
| |
| <para>The <structfield>x</structfield>, |
| <structfield>y</structfield>, <structfield>width</structfield> and |
| <structfield>height</structfield> fields moved into &v4l2-rect; |
| substructure <structfield>c</structfield> of struct |
| <structname>v4l2_crop</structname>. The |
| <structfield>decimation</structfield> field was dropped. In the V4L2 |
| API the scaling factor is implied by the size of the cropping |
| rectangle and the size of the captured or overlaid image.</para> |
| |
| <para>The <constant>VIDEO_CAPTURE_ODD</constant> |
| and <constant>VIDEO_CAPTURE_EVEN</constant> flags to capture only the |
| odd or even field, respectively, were replaced by |
| <constant>V4L2_FIELD_TOP</constant> and |
| <constant>V4L2_FIELD_BOTTOM</constant> in the field named |
| <structfield>field</structfield> of &v4l2-pix-format; and |
| &v4l2-window;. These structures are used to select a capture or |
| overlay format with the &VIDIOC-S-FMT; ioctl.</para> |
| </section> |
| |
| <section> |
| <title>Reading Images, Memory Mapping</title> |
| |
| <section> |
| <title>Capturing using the read method</title> |
| |
| <para>There is no essential difference between reading images |
| from a V4L or V4L2 device using the &func-read; function, however V4L2 |
| drivers are not required to support this I/O method. Applications can |
| determine if the function is available with the &VIDIOC-QUERYCAP; |
| ioctl. All V4L2 devices exchanging data with applications must support |
| the &func-select; and &func-poll; functions.</para> |
| |
| <para>To select an image format and size, V4L provides the |
| <constant>VIDIOCSPICT</constant> and <constant>VIDIOCSWIN</constant> |
| ioctls. V4L2 uses the general-purpose data format negotiation ioctls |
| &VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a |
| &v4l2-format; as argument, here the &v4l2-pix-format; named |
| <structfield>pix</structfield> of its <structfield>fmt</structfield> |
| union is used.</para> |
| |
| <para>For more information about the V4L2 read interface see |
| <xref linkend="rw" />.</para> |
| </section> |
| <section> |
| <title>Capturing using memory mapping</title> |
| |
| <para>Applications can read from V4L devices by mapping |
| buffers in device memory, or more often just buffers allocated in |
| DMA-able system memory, into their address space. This avoids the data |
| copying overhead of the read method. V4L2 supports memory mapping as |
| well, with a few differences.</para> |
| |
| <informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>V4L</entry> |
| <entry>V4L2</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry></entry> |
| <entry>The image format must be selected before |
| buffers are allocated, with the &VIDIOC-S-FMT; ioctl. When no format |
| is selected the driver may use the last, possibly by another |
| application requested format.</entry> |
| </row> |
| <row> |
| <entry><para>Applications cannot change the number of |
| buffers. The it is built into the driver, unless it has a module |
| option to change the number when the driver module is |
| loaded.</para></entry> |
| <entry><para>The &VIDIOC-REQBUFS; ioctl allocates the |
| desired number of buffers, this is a required step in the initialization |
| sequence.</para></entry> |
| </row> |
| <row> |
| <entry><para>Drivers map all buffers as one contiguous |
| range of memory. The <constant>VIDIOCGMBUF</constant> ioctl is |
| available to query the number of buffers, the offset of each buffer |
| from the start of the virtual file, and the overall amount of memory |
| used, which can be used as arguments for the &func-mmap; |
| function.</para></entry> |
| <entry><para>Buffers are individually mapped. The |
| offset and size of each buffer can be determined with the |
| &VIDIOC-QUERYBUF; ioctl.</para></entry> |
| </row> |
| <row> |
| <entry><para>The <constant>VIDIOCMCAPTURE</constant> |
| ioctl prepares a buffer for capturing. It also determines the image |
| format for this buffer. The ioctl returns immediately, eventually with |
| an &EAGAIN; if no video signal had been detected. When the driver |
| supports more than one buffer applications can call the ioctl multiple |
| times and thus have multiple outstanding capture |
| requests.</para><para>The <constant>VIDIOCSYNC</constant> ioctl |
| suspends execution until a particular buffer has been |
| filled.</para></entry> |
| <entry><para>Drivers maintain an incoming and outgoing |
| queue. &VIDIOC-QBUF; enqueues any empty buffer into the incoming |
| queue. Filled buffers are dequeued from the outgoing queue with the |
| &VIDIOC-DQBUF; ioctl. To wait until filled buffers become available this |
| function, &func-select; or &func-poll; can be used. The |
| &VIDIOC-STREAMON; ioctl must be called once after enqueuing one or |
| more buffers to start capturing. Its counterpart |
| &VIDIOC-STREAMOFF; stops capturing and dequeues all buffers from both |
| queues. Applications can query the signal status, if known, with the |
| &VIDIOC-ENUMINPUT; ioctl.</para></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <para>For a more in-depth discussion of memory mapping and |
| examples, see <xref linkend="mmap" />.</para> |
| </section> |
| </section> |
| |
| <section> |
| <title>Reading Raw VBI Data</title> |
| |
| <para>Originally the V4L API did not specify a raw VBI capture |
| interface, only the device file <filename>/dev/vbi</filename> was |
| reserved for this purpose. The only driver supporting this interface |
| was the BTTV driver, de-facto defining the V4L VBI interface. Reading |
| from the device yields a raw VBI image with the following |
| parameters:<informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>&v4l2-vbi-format;</entry> |
| <entry>V4L, BTTV driver</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry>sampling_rate</entry> |
| <entry>28636363 Hz NTSC (or any other 525-line |
| standard); 35468950 Hz PAL and SECAM (625-line standards)</entry> |
| </row> |
| <row> |
| <entry>offset</entry> |
| <entry>?</entry> |
| </row> |
| <row> |
| <entry>samples_per_line</entry> |
| <entry>2048</entry> |
| </row> |
| <row> |
| <entry>sample_format</entry> |
| <entry>V4L2_PIX_FMT_GREY. The last four bytes (a |
| machine endianess integer) contain a frame counter.</entry> |
| </row> |
| <row> |
| <entry>start[]</entry> |
| <entry>10, 273 NTSC; 22, 335 PAL and SECAM</entry> |
| </row> |
| <row> |
| <entry>count[]</entry> |
| <entry><para>16, 16<footnote><para>Old driver |
| versions used different values, eventually the custom |
| <constant>BTTV_VBISIZE</constant> ioctl was added to query the |
| correct values.</para></footnote></para></entry> |
| </row> |
| <row> |
| <entry>flags</entry> |
| <entry>0</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>Undocumented in the V4L specification, in Linux 2.3 the |
| <constant>VIDIOCGVBIFMT</constant> and |
| <constant>VIDIOCSVBIFMT</constant> ioctls using struct |
| <structname>vbi_format</structname> were added to determine the VBI |
| image parameters. These ioctls are only partially compatible with the |
| V4L2 VBI interface specified in <xref linkend="raw-vbi" />.</para> |
| |
| <para>An <structfield>offset</structfield> field does not |
| exist, <structfield>sample_format</structfield> is supposed to be |
| <constant>VIDEO_PALETTE_RAW</constant>, equivalent to |
| <constant>V4L2_PIX_FMT_GREY</constant>. The remaining fields are |
| probably equivalent to &v4l2-vbi-format;.</para> |
| |
| <para>Apparently only the Zoran (ZR 36120) driver implements |
| these ioctls. The semantics differ from those specified for V4L2 in two |
| ways. The parameters are reset on &func-open; and |
| <constant>VIDIOCSVBIFMT</constant> always returns an &EINVAL; if the |
| parameters are invalid.</para> |
| </section> |
| |
| <section> |
| <title>Miscellaneous</title> |
| |
| <para>V4L2 has no equivalent of the |
| <constant>VIDIOCGUNIT</constant> ioctl. Applications can find the VBI |
| device associated with a video capture device (or vice versa) by |
| reopening the device and requesting VBI data. For details see |
| <xref linkend="open" />.</para> |
| |
| <para>No replacement exists for <constant>VIDIOCKEY</constant>, |
| and the V4L functions for microcode programming. A new interface for |
| MPEG compression and playback devices is documented in <xref |
| linkend="extended-controls" />.</para> |
| </section> |
| |
| </section> |
| |
| <section id="hist-v4l2"> |
| <title>Changes of the V4L2 API</title> |
| |
| <para>Soon after the V4L API was added to the kernel it was |
| criticised as too inflexible. In August 1998 Bill Dirks proposed a |
| number of improvements and began to work on documentation, example |
| drivers and applications. With the help of other volunteers this |
| eventually became the V4L2 API, not just an extension but a |
| replacement for the V4L API. However it took another four years and |
| two stable kernel releases until the new API was finally accepted for |
| inclusion into the kernel in its present form.</para> |
| |
| <section> |
| <title>Early Versions</title> |
| <para>1998-08-20: First version.</para> |
| |
| <para>1998-08-27: The &func-select; function was introduced.</para> |
| |
| <para>1998-09-10: New video standard interface.</para> |
| |
| <para>1998-09-18: The <constant>VIDIOC_NONCAP</constant> ioctl |
| was replaced by the otherwise meaningless <constant>O_TRUNC</constant> |
| &func-open; flag, and the aliases <constant>O_NONCAP</constant> and |
| <constant>O_NOIO</constant> were defined. Applications can set this |
| flag if they intend to access controls only, as opposed to capture |
| applications which need exclusive access. The |
| <constant>VIDEO_STD_XXX</constant> identifiers are now ordinals |
| instead of flags, and the <function>video_std_construct()</function> |
| helper function takes id and transmission arguments.</para> |
| |
| <para>1998-09-28: Revamped video standard. Made video controls |
| individually enumerable.</para> |
| |
| <para>1998-10-02: The <structfield>id</structfield> field was |
| removed from struct <structname>video_standard</structname> and the |
| color subcarrier fields were renamed. The &VIDIOC-QUERYSTD; ioctl was |
| renamed to &VIDIOC-ENUMSTD;, &VIDIOC-G-INPUT; to &VIDIOC-ENUMINPUT;. A |
| first draft of the Codec API was released.</para> |
| |
| <para>1998-11-08: Many minor changes. Most symbols have been |
| renamed. Some material changes to &v4l2-capability;.</para> |
| |
| <para>1998-11-12: The read/write directon of some ioctls was misdefined.</para> |
| |
| <para>1998-11-14: <constant>V4L2_PIX_FMT_RGB24</constant> |
| changed to <constant>V4L2_PIX_FMT_BGR24</constant>, and |
| <constant>V4L2_PIX_FMT_RGB32</constant> changed to |
| <constant>V4L2_PIX_FMT_BGR32</constant>. Audio controls are now |
| accessible with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls under |
| names starting with <constant>V4L2_CID_AUDIO</constant>. The |
| <constant>V4L2_MAJOR</constant> define was removed from |
| <filename>videodev.h</filename> since it was only used once in the |
| <filename>videodev</filename> kernel module. The |
| <constant>YUV422</constant> and <constant>YUV411</constant> planar |
| image formats were added.</para> |
| |
| <para>1998-11-28: A few ioctl symbols changed. Interfaces for codecs and |
| video output devices were added.</para> |
| |
| <para>1999-01-14: A raw VBI capture interface was added.</para> |
| |
| <para>1999-01-19: The <constant>VIDIOC_NEXTBUF</constant> ioctl |
| was removed.</para> |
| </section> |
| |
| <section> |
| <title>V4L2 Version 0.16 1999-01-31</title> |
| <para>1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF |
| are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added |
| digital zoom (cropping) controls.</para> |
| </section> |
| |
| <!-- Where's 0.17? mhs couldn't find that videodev.h, perhaps Bill |
| forgot to bump the version number or never released it. --> |
| |
| <section> |
| <title>V4L2 Version 0.18 1999-03-16</title> |
| <para>Added a v4l to V4L2 ioctl compatibility layer to |
| videodev.c. Driver writers, this changes how you implement your ioctl |
| handler. See the Driver Writer's Guide. Added some more control id |
| codes.</para> |
| </section> |
| |
| <section> |
| <title>V4L2 Version 0.19 1999-06-05</title> |
| <para>1999-03-18: Fill in the category and catname fields of |
| v4l2_queryctrl objects before passing them to the driver. Required a |
| minor change to the VIDIOC_QUERYCTRL handlers in the sample |
| drivers.</para> |
| <para>1999-03-31: Better compatibility for v4l memory capture |
| ioctls. Requires changes to drivers to fully support new compatibility |
| features, see Driver Writer's Guide and v4l2cap.c. Added new control |
| IDs: V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P, |
| and _YUV411P to _YUV411P.</para> |
| <para>1999-04-04: Added a few more control IDs.</para> |
| <para>1999-04-07: Added the button control type.</para> |
| <para>1999-05-02: Fixed a typo in videodev.h, and added the |
| V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.</para> |
| <para>1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing |
| a malfunction of this ioctl.</para> |
| <para>1999-06-05: Changed the value of |
| V4L2_CID_WHITENESS.</para> |
| </section> |
| |
| <section> |
| <title>V4L2 Version 0.20 (1999-09-10)</title> |
| |
| <para>Version 0.20 introduced a number of changes which were |
| <emphasis>not backward compatible</emphasis> with 0.19 and earlier |
| versions. Purpose of these changes was to simplify the API, while |
| making it more extensible and following common Linux driver API |
| conventions.</para> |
| |
| <orderedlist> |
| <listitem> |
| <para>Some typos in <constant>V4L2_FMT_FLAG</constant> |
| symbols were fixed. &v4l2-clip; was changed for compatibility with |
| v4l. (1999-08-30)</para> |
| </listitem> |
| |
| <listitem> |
| <para><constant>V4L2_TUNER_SUB_LANG1</constant> was added. |
| (1999-09-05)</para> |
| </listitem> |
| |
| <listitem> |
| <para>All ioctl() commands that used an integer argument now |
| take a pointer to an integer. Where it makes sense, ioctls will return |
| the actual new value in the integer pointed to by the argument, a |
| common convention in the V4L2 API. The affected ioctls are: |
| VIDIOC_PREVIEW, VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ, |
| VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example |
| <programlisting> |
| err = ioctl (fd, VIDIOC_XXX, V4L2_XXX); |
| </programlisting> becomes <programlisting> |
| int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a); |
| </programlisting> |
| </para> |
| </listitem> |
| |
| <listitem> |
| <para>All the different get- and set-format commands were |
| swept into one &VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctl taking a union |
| and a type field selecting the union member as parameter. Purpose is to |
| simplify the API by eliminating several ioctls and to allow new and |
| driver private data streams without adding new ioctls.</para> |
| |
| <para>This change obsoletes the following ioctls: |
| <constant>VIDIOC_S_INFMT</constant>, |
| <constant>VIDIOC_G_INFMT</constant>, |
| <constant>VIDIOC_S_OUTFMT</constant>, |
| <constant>VIDIOC_G_OUTFMT</constant>, |
| <constant>VIDIOC_S_VBIFMT</constant> and |
| <constant>VIDIOC_G_VBIFMT</constant>. The image format structure |
| <structname>v4l2_format</structname> was renamed to &v4l2-pix-format;, |
| while &v4l2-format; is now the envelopping structure for all format |
| negotiations.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Similar to the changes above, the |
| <constant>VIDIOC_G_PARM</constant> and |
| <constant>VIDIOC_S_PARM</constant> ioctls were merged with |
| <constant>VIDIOC_G_OUTPARM</constant> and |
| <constant>VIDIOC_S_OUTPARM</constant>. A |
| <structfield>type</structfield> field in the new &v4l2-streamparm; |
| selects the respective union member.</para> |
| |
| <para>This change obsoletes the |
| <constant>VIDIOC_G_OUTPARM</constant> and |
| <constant>VIDIOC_S_OUTPARM</constant> ioctls.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Control enumeration was simplified, and two new |
| control flags were introduced and one dropped. The |
| <structfield>catname</structfield> field was replaced by a |
| <structfield>group</structfield> field.</para> |
| |
| <para>Drivers can now flag unsupported and temporarily |
| unavailable controls with <constant>V4L2_CTRL_FLAG_DISABLED</constant> |
| and <constant>V4L2_CTRL_FLAG_GRABBED</constant> respectively. The |
| <structfield>group</structfield> name indicates a possibly narrower |
| classification than the <structfield>category</structfield>. In other |
| words, there may be multiple groups within a category. Controls within |
| a group would typically be drawn within a group box. Controls in |
| different categories might have a greater separation, or may even |
| appear in separate windows.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &v4l2-buffer; <structfield>timestamp</structfield> |
| was changed to a 64 bit integer, containing the sampling or output |
| time of the frame in nanoseconds. Additionally timestamps will be in |
| absolute system time, not starting from zero at the beginning of a |
| stream. The data type name for timestamps is stamp_t, defined as a |
| signed 64-bit integer. Output devices should not send a buffer out |
| until the time in the timestamp field has arrived. I would like to |
| follow SGI's lead, and adopt a multimedia timestamping system like |
| their UST (Unadjusted System Time). See |
| http://reality.sgi.com/cpirazzi_engr/lg/time/intro.html. [This link is |
| no longer valid.] UST uses timestamps that are 64-bit signed integers |
| (not struct timeval's) and given in nanosecond units. The UST clock |
| starts at zero when the system is booted and runs continuously and |
| uniformly. It takes a little over 292 years for UST to overflow. There |
| is no way to set the UST clock. The regular Linux time-of-day clock |
| can be changed periodically, which would cause errors if it were being |
| used for timestamping a multimedia stream. A real UST style clock will |
| require some support in the kernel that is not there yet. But in |
| anticipation, I will change the timestamp field to a 64-bit integer, |
| and I will change the v4l2_masterclock_gettime() function (used only |
| by drivers) to return a 64-bit integer.</para> |
| </listitem> |
| |
| <listitem> |
| <para>A <structfield>sequence</structfield> field was added |
| to &v4l2-buffer;. The <structfield>sequence</structfield> field counts |
| captured frames, it is ignored by output devices. When a capture |
| driver drops a frame, the sequence number of that frame is |
| skipped.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 Version 0.20 incremental changes</title> |
| <!-- Version number didn't change anymore, reason unknown. --> |
| |
| <para>1999-12-23: In &v4l2-vbi-format; the |
| <structfield>reserved1</structfield> field became |
| <structfield>offset</structfield>. Previously drivers were required to |
| clear the <structfield>reserved1</structfield> field.</para> |
| |
| <para>2000-01-13: The |
| <constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant> flag was added.</para> |
| |
| <para>2000-07-31: The <filename>linux/poll.h</filename> header |
| is now included by <filename>videodev.h</filename> for compatibility |
| with the original <filename>videodev.h</filename> file.</para> |
| |
| <para>2000-11-20: <constant>V4L2_TYPE_VBI_OUTPUT</constant> and |
| <constant>V4L2_PIX_FMT_Y41P</constant> were added.</para> |
| |
| <para>2000-11-25: <constant>V4L2_TYPE_VBI_INPUT</constant> was |
| added.</para> |
| |
| <para>2000-12-04: A couple typos in symbol names were fixed.</para> |
| |
| <para>2001-01-18: To avoid namespace conflicts the |
| <constant>fourcc</constant> macro defined in the |
| <filename>videodev.h</filename> header file was renamed to |
| <constant>v4l2_fourcc</constant>.</para> |
| |
| <para>2001-01-25: A possible driver-level compatibility problem |
| between the <filename>videodev.h</filename> file in Linux 2.4.0 and |
| the <filename>videodev.h</filename> file included in the |
| <filename>videodevX</filename> patch was fixed. Users of an earlier |
| version of <filename>videodevX</filename> on Linux 2.4.0 should |
| recompile their V4L and V4L2 drivers.</para> |
| |
| <para>2001-01-26: A possible kernel-level incompatibility |
| between the <filename>videodev.h</filename> file in the |
| <filename>videodevX</filename> patch and the |
| <filename>videodev.h</filename> file in Linux 2.2.x with devfs patches |
| applied was fixed.</para> |
| |
| <para>2001-03-02: Certain V4L ioctls which pass data in both |
| direction although they are defined with read-only parameter, did not |
| work correctly through the backward compatibility layer. |
| [Solution?]</para> |
| |
| <para>2001-04-13: Big endian 16-bit RGB formats were added.</para> |
| |
| <para>2001-09-17: New YUV formats and the &VIDIOC-G-FREQUENCY; and |
| &VIDIOC-S-FREQUENCY; ioctls were added. (The old |
| <constant>VIDIOC_G_FREQ</constant> and |
| <constant>VIDIOC_S_FREQ</constant> ioctls did not take multiple tuners |
| into account.)</para> |
| |
| <para>2000-09-18: <constant>V4L2_BUF_TYPE_VBI</constant> was |
| added. This may <emphasis>break compatibility</emphasis> as the |
| &VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctls may fail now if the struct |
| <structname>v4l2_fmt</structname> <structfield>type</structfield> |
| field does not contain <constant>V4L2_BUF_TYPE_VBI</constant>. In the |
| documentation of the &v4l2-vbi-format; |
| <structfield>offset</structfield> field the ambiguous phrase "rising |
| edge" was changed to "leading edge".</para> |
| </section> |
| |
| <section> |
| <title>V4L2 Version 0.20 2000-11-23</title> |
| |
| <para>A number of changes were made to the raw VBI |
| interface.</para> |
| |
| <orderedlist> |
| <listitem> |
| <para>Figures clarifying the line numbering scheme were |
| added to the V4L2 API specification. The |
| <structfield>start</structfield>[0] and |
| <structfield>start</structfield>[1] fields no longer count line |
| numbers beginning at zero. Rationale: a) The previous definition was |
| unclear. b) The <structfield>start</structfield>[] values are ordinal |
| numbers. c) There is no point in inventing a new line numbering |
| scheme. We now use line number as defined by ITU-R, period. |
| Compatibility: Add one to the start values. Applications depending on |
| the previous semantics may not function correctly.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The restriction "count[0] > 0 and count[1] > 0" |
| has been relaxed to "(count[0] + count[1]) > 0". Rationale: |
| Drivers may allocate resources at scan line granularity and some data |
| services are transmitted only on the first field. The comment that |
| both <structfield>count</structfield> values will usually be equal is |
| misleading and pointless and has been removed. This change |
| <emphasis>breaks compatibility</emphasis> with earlier versions: |
| Drivers may return EINVAL, applications may not function |
| correctly.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Drivers are again permitted to return negative |
| (unknown) start values as proposed earlier. Why this feature was |
| dropped is unclear. This change may <emphasis>break |
| compatibility</emphasis> with applications depending on the start |
| values being positive. The use of <constant>EBUSY</constant> and |
| <constant>EINVAL</constant> error codes with the &VIDIOC-S-FMT; ioctl |
| was clarified. The &EBUSY; was finally documented, and the |
| <structfield>reserved2</structfield> field which was previously |
| mentioned only in the <filename>videodev.h</filename> header |
| file.</para> |
| </listitem> |
| |
| <listitem> |
| <para>New buffer types |
| <constant>V4L2_TYPE_VBI_INPUT</constant> and |
| <constant>V4L2_TYPE_VBI_OUTPUT</constant> were added. The former is an |
| alias for the old <constant>V4L2_TYPE_VBI</constant>, the latter was |
| missing in the <filename>videodev.h</filename> file.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 Version 0.20 2002-07-25</title> |
| <para>Added sliced VBI interface proposal.</para> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.5.46, 2002-10</title> |
| |
| <para>Around October-November 2002, prior to an announced |
| feature freeze of Linux 2.5, the API was revised, drawing from |
| experience with V4L2 0.20. This unnamed version was finally merged |
| into Linux 2.5.46.</para> |
| |
| <orderedlist> |
| <listitem> |
| <para>As specified in <xref linkend="related" />, drivers |
| must make related device functions available under all minor device |
| numbers.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &func-open; function requires access mode |
| <constant>O_RDWR</constant> regardless of the device type. All V4L2 |
| drivers exchanging data with applications must support the |
| <constant>O_NONBLOCK</constant> flag. The <constant>O_NOIO</constant> |
| flag, a V4L2 symbol which aliased the meaningless |
| <constant>O_TRUNC</constant> to indicate accesses without data |
| exchange (panel applications) was dropped. Drivers must stay in "panel |
| mode" until the application attempts to initiate a data exchange, see |
| <xref linkend="open" />.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &v4l2-capability; changed dramatically. Note that |
| also the size of the structure changed, which is encoded in the ioctl |
| request code, thus older V4L2 devices will respond with an &EINVAL; to |
| the new &VIDIOC-QUERYCAP; ioctl.</para> |
| |
| <para>There are new fields to identify the driver, a new RDS |
| device function <constant>V4L2_CAP_RDS_CAPTURE</constant>, the |
| <constant>V4L2_CAP_AUDIO</constant> flag indicates if the device has |
| any audio connectors, another I/O capability |
| <constant>V4L2_CAP_ASYNCIO</constant> can be flagged. In response to |
| these changes the <structfield>type</structfield> field became a bit |
| set and was merged into the <structfield>flags</structfield> field. |
| <constant>V4L2_FLAG_TUNER</constant> was renamed to |
| <constant>V4L2_CAP_TUNER</constant>, |
| <constant>V4L2_CAP_VIDEO_OVERLAY</constant> replaced |
| <constant>V4L2_FLAG_PREVIEW</constant> and |
| <constant>V4L2_CAP_VBI_CAPTURE</constant> and |
| <constant>V4L2_CAP_VBI_OUTPUT</constant> replaced |
| <constant>V4L2_FLAG_DATA_SERVICE</constant>. |
| <constant>V4L2_FLAG_READ</constant> and |
| <constant>V4L2_FLAG_WRITE</constant> were merged into |
| <constant>V4L2_CAP_READWRITE</constant>.</para> |
| |
| <para>The redundant fields |
| <structfield>inputs</structfield>, <structfield>outputs</structfield> |
| and <structfield>audios</structfield> were removed. These properties |
| can be determined as described in <xref linkend="video" /> and <xref |
| linkend="audio" />.</para> |
| |
| <para>The somewhat volatile and therefore barely useful |
| fields <structfield>maxwidth</structfield>, |
| <structfield>maxheight</structfield>, |
| <structfield>minwidth</structfield>, |
| <structfield>minheight</structfield>, |
| <structfield>maxframerate</structfield> were removed. This information |
| is available as described in <xref linkend="format" /> and |
| <xref linkend="standard" />.</para> |
| |
| <para><constant>V4L2_FLAG_SELECT</constant> was removed. We |
| believe the select() function is important enough to require support |
| of it in all V4L2 drivers exchanging data with applications. The |
| redundant <constant>V4L2_FLAG_MONOCHROME</constant> flag was removed, |
| this information is available as described in <xref |
| linkend="format" />.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-input; the |
| <structfield>assoc_audio</structfield> field and the |
| <structfield>capability</structfield> field and its only flag |
| <constant>V4L2_INPUT_CAP_AUDIO</constant> was replaced by the new |
| <structfield>audioset</structfield> field. Instead of linking one |
| video input to one audio input this field reports all audio inputs |
| this video input combines with.</para> |
| |
| <para>New fields are <structfield>tuner</structfield> |
| (reversing the former link from tuners to video inputs), |
| <structfield>std</structfield> and |
| <structfield>status</structfield>.</para> |
| |
| <para>Accordingly &v4l2-output; lost its |
| <structfield>capability</structfield> and |
| <structfield>assoc_audio</structfield> fields. |
| <structfield>audioset</structfield>, |
| <structfield>modulator</structfield> and |
| <structfield>std</structfield> where added instead.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &v4l2-audio; field |
| <structfield>audio</structfield> was renamed to |
| <structfield>index</structfield>, for consistency with other |
| structures. A new capability flag |
| <constant>V4L2_AUDCAP_STEREO</constant> was added to indicated if the |
| audio input in question supports stereo sound. |
| <constant>V4L2_AUDCAP_EFFECTS</constant> and the corresponding |
| <constant>V4L2_AUDMODE</constant> flags where removed. This can be |
| easily implemented using controls. (However the same applies to AVL |
| which is still there.)</para> |
| |
| <para>Again for consistency the &v4l2-audioout; field |
| <structfield>audio</structfield> was renamed to |
| <structfield>index</structfield>.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &v4l2-tuner; |
| <structfield>input</structfield> field was replaced by an |
| <structfield>index</structfield> field, permitting devices with |
| multiple tuners. The link between video inputs and tuners is now |
| reversed, inputs point to their tuner. The |
| <structfield>std</structfield> substructure became a |
| simple set (more about this below) and moved into &v4l2-input;. A |
| <structfield>type</structfield> field was added.</para> |
| |
| <para>Accordingly in &v4l2-modulator; the |
| <structfield>output</structfield> was replaced by an |
| <structfield>index</structfield> field.</para> |
| |
| <para>In &v4l2-frequency; the |
| <structfield>port</structfield> field was replaced by a |
| <structfield>tuner</structfield> field containing the respective tuner |
| or modulator index number. A tuner <structfield>type</structfield> |
| field was added and the <structfield>reserved</structfield> field |
| became larger for future extensions (satellite tuners in |
| particular).</para> |
| </listitem> |
| |
| <listitem> |
| <para>The idea of completely transparent video standards was |
| dropped. Experience showed that applications must be able to work with |
| video standards beyond presenting the user a menu. Instead of |
| enumerating supported standards with an ioctl applications can now |
| refer to standards by &v4l2-std-id; and symbols defined in the |
| <filename>videodev2.h</filename> header file. For details see <xref |
| linkend="standard" />. The &VIDIOC-G-STD; and |
| &VIDIOC-S-STD; now take a pointer to this type as argument. |
| &VIDIOC-QUERYSTD; was added to autodetect the received standard, if |
| the hardware has this capability. In &v4l2-standard; an |
| <structfield>index</structfield> field was added for &VIDIOC-ENUMSTD;. |
| A &v4l2-std-id; field named <structfield>id</structfield> was added as |
| machine readable identifier, also replacing the |
| <structfield>transmission</structfield> field. The misleading |
| <structfield>framerate</structfield> field was renamed |
| to <structfield>frameperiod</structfield>. The now obsolete |
| <structfield>colorstandard</structfield> information, originally |
| needed to distguish between variations of standards, were |
| removed.</para> |
| |
| <para>Struct <structname>v4l2_enumstd</structname> ceased to |
| be. &VIDIOC-ENUMSTD; now takes a pointer to a &v4l2-standard; |
| directly. The information which standards are supported by a |
| particular video input or output moved into &v4l2-input; and |
| &v4l2-output; fields named <structfield>std</structfield>, |
| respectively.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &v4l2-queryctrl; fields |
| <structfield>category</structfield> and |
| <structfield>group</structfield> did not catch on and/or were not |
| implemented as expected and therefore removed.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &VIDIOC-TRY-FMT; ioctl was added to negotiate data |
| formats as with &VIDIOC-S-FMT;, but without the overhead of |
| programming the hardware and regardless of I/O in progress.</para> |
| |
| <para>In &v4l2-format; the <structfield>fmt</structfield> |
| union was extended to contain &v4l2-window;. All image format |
| negotiations are now possible with <constant>VIDIOC_G_FMT</constant>, |
| <constant>VIDIOC_S_FMT</constant> and |
| <constant>VIDIOC_TRY_FMT</constant>; ioctl. The |
| <constant>VIDIOC_G_WIN</constant> and |
| <constant>VIDIOC_S_WIN</constant> ioctls to prepare for a video |
| overlay were removed. The <structfield>type</structfield> field |
| changed to type &v4l2-buf-type; and the buffer type names changed as |
| follows.<informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>Old defines</entry> |
| <entry>&v4l2-buf-type;</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_CAPTURE</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant></entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_CODECIN</constant></entry> |
| <entry>Omitted for now</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_CODECOUT</constant></entry> |
| <entry>Omitted for now</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_EFFECTSIN</constant></entry> |
| <entry>Omitted for now</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_EFFECTSIN2</constant></entry> |
| <entry>Omitted for now</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_EFFECTSOUT</constant></entry> |
| <entry>Omitted for now</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_VIDEOOUT</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_VBI_CAPTURE</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_VBI_OUTPUT</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant></entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_BUF_TYPE_PRIVATE_BASE</constant></entry> |
| <entry><constant>V4L2_BUF_TYPE_PRIVATE</constant></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-fmtdesc; a &v4l2-buf-type; field named |
| <structfield>type</structfield> was added as in &v4l2-format;. The |
| <constant>VIDIOC_ENUM_FBUFFMT</constant> ioctl is no longer needed and |
| was removed. These calls can be replaced by &VIDIOC-ENUM-FMT; with |
| type <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-pix-format; the |
| <structfield>depth</structfield> field was removed, assuming |
| applications which recognize the format by its four-character-code |
| already know the color depth, and others do not care about it. The |
| same rationale lead to the removal of the |
| <constant>V4L2_FMT_FLAG_COMPRESSED</constant> flag. The |
| <constant>V4L2_FMT_FLAG_SWCONVECOMPRESSED</constant> flag was removed |
| because drivers are not supposed to convert images in kernel space. A |
| user library of conversion functions should be provided instead. The |
| <constant>V4L2_FMT_FLAG_BYTESPERLINE</constant> flag was redundant. |
| Applications can set the <structfield>bytesperline</structfield> field |
| to zero to get a reasonable default. Since the remaining flags were |
| replaced as well, the <structfield>flags</structfield> field itself |
| was removed.</para> |
| <para>The interlace flags were replaced by a &v4l2-field; |
| value in a newly added <structfield>field</structfield> |
| field.<informaltable> |
| <tgroup cols="2"> |
| <thead> |
| <row> |
| <entry>Old flag</entry> |
| <entry>&v4l2-field;</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant></entry> |
| <entry>?</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_FMT_FLAG_INTERLACED</constant> |
| = <constant>V4L2_FMT_FLAG_COMBINED</constant></entry> |
| <entry><constant>V4L2_FIELD_INTERLACED</constant></entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_FMT_FLAG_TOPFIELD</constant> |
| = <constant>V4L2_FMT_FLAG_ODDFIELD</constant></entry> |
| <entry><constant>V4L2_FIELD_TOP</constant></entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_FMT_FLAG_BOTFIELD</constant> |
| = <constant>V4L2_FMT_FLAG_EVENFIELD</constant></entry> |
| <entry><constant>V4L2_FIELD_BOTTOM</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_FIELD_SEQ_TB</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_FIELD_SEQ_BT</constant></entry> |
| </row> |
| <row> |
| <entry><constant>-</constant></entry> |
| <entry><constant>V4L2_FIELD_ALTERNATE</constant></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable></para> |
| |
| <para>The color space flags were replaced by a |
| &v4l2-colorspace; value in a newly added |
| <structfield>colorspace</structfield> field, where one of |
| <constant>V4L2_COLORSPACE_SMPTE170M</constant>, |
| <constant>V4L2_COLORSPACE_BT878</constant>, |
| <constant>V4L2_COLORSPACE_470_SYSTEM_M</constant> or |
| <constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant> replaces |
| <constant>V4L2_FMT_CS_601YUV</constant>.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-requestbuffers; the |
| <structfield>type</structfield> field was properly defined as |
| &v4l2-buf-type;. Buffer types changed as mentioned above. A new |
| <structfield>memory</structfield> field of type &v4l2-memory; was |
| added to distinguish between I/O methods using buffers allocated |
| by the driver or the application. See <xref linkend="io" /> for |
| details.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-buffer; the <structfield>type</structfield> |
| field was properly defined as &v4l2-buf-type;. Buffer types changed as |
| mentioned above. A <structfield>field</structfield> field of type |
| &v4l2-field; was added to indicate if a buffer contains a top or |
| bottom field. The old field flags were removed. Since no unadjusted |
| system time clock was added to the kernel as planned, the |
| <structfield>timestamp</structfield> field changed back from type |
| stamp_t, an unsigned 64 bit integer expressing the sample time in |
| nanoseconds, to struct <structname>timeval</structname>. With the |
| addition of a second memory mapping method the |
| <structfield>offset</structfield> field moved into union |
| <structfield>m</structfield>, and a new |
| <structfield>memory</structfield> field of type &v4l2-memory; was |
| added to distinguish between I/O methods. See <xref linkend="io" /> |
| for details.</para> |
| |
| <para>The <constant>V4L2_BUF_REQ_CONTIG</constant> |
| flag was used by the V4L compatibility layer, after changes to this |
| code it was no longer needed. The |
| <constant>V4L2_BUF_ATTR_DEVICEMEM</constant> flag would indicate if |
| the buffer was indeed allocated in device memory rather than DMA-able |
| system memory. It was barely useful and so was removed.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-framebuffer; the |
| <structfield>base[3]</structfield> array anticipating double- and |
| triple-buffering in off-screen video memory, however without defining |
| a synchronization mechanism, was replaced by a single pointer. The |
| <constant>V4L2_FBUF_CAP_SCALEUP</constant> and |
| <constant>V4L2_FBUF_CAP_SCALEDOWN</constant> flags were removed. |
| Applications can determine this capability more accurately using the |
| new cropping and scaling interface. The |
| <constant>V4L2_FBUF_CAP_CLIPPING</constant> flag was replaced by |
| <constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant> and |
| <constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant>.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-clip; the <structfield>x</structfield>, |
| <structfield>y</structfield>, <structfield>width</structfield> and |
| <structfield>height</structfield> field moved into a |
| <structfield>c</structfield> substructure of type &v4l2-rect;. The |
| <structfield>x</structfield> and <structfield>y</structfield> fields |
| were renamed to <structfield>left</structfield> and |
| <structfield>top</structfield>, &ie; offsets to a context dependent |
| origin.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-window; the <structfield>x</structfield>, |
| <structfield>y</structfield>, <structfield>width</structfield> and |
| <structfield>height</structfield> field moved into a |
| <structfield>w</structfield> substructure as above. A |
| <structfield>field</structfield> field of type %v4l2-field; was added |
| to distinguish between field and frame (interlaced) overlay.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The digital zoom interface, including struct |
| <structname>v4l2_zoomcap</structname>, struct |
| <structname>v4l2_zoom</structname>, |
| <constant>V4L2_ZOOM_NONCAP</constant> and |
| <constant>V4L2_ZOOM_WHILESTREAMING</constant> was replaced by a new |
| cropping and scaling interface. The previously unused struct |
| <structname>v4l2_cropcap</structname> and |
| <structname>v4l2_crop</structname> where redefined for this purpose. |
| See <xref linkend="crop" /> for details.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-vbi-format; the |
| <structfield>SAMPLE_FORMAT</structfield> field now contains a |
| four-character-code as used to identify video image formats and |
| <constant>V4L2_PIX_FMT_GREY</constant> replaces the |
| <constant>V4L2_VBI_SF_UBYTE</constant> define. The |
| <structfield>reserved</structfield> field was extended.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In &v4l2-captureparm; the type of the |
| <structfield>timeperframe</structfield> field changed from unsigned |
| long to &v4l2-fract;. This allows the accurate expression of multiples |
| of the NTSC-M frame rate 30000 / 1001. A new field |
| <structfield>readbuffers</structfield> was added to control the driver |
| behaviour in read I/O mode.</para> |
| |
| <para>Similar changes were made to &v4l2-outputparm;.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The struct <structname>v4l2_performance</structname> |
| and <constant>VIDIOC_G_PERF</constant> ioctl were dropped. Except when |
| using the <link linkend="rw">read/write I/O method</link>, which is |
| limited anyway, this information is already available to |
| applications.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The example transformation from RGB to YCbCr color |
| space in the old V4L2 documentation was inaccurate, this has been |
| corrected in <xref linkend="pixfmt" />.<!-- 0.5670G should be |
| 0.587, and 127/112 != 255/224 --></para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 2003-06-19</title> |
| |
| <orderedlist> |
| <listitem> |
| <para>A new capability flag |
| <constant>V4L2_CAP_RADIO</constant> was added for radio devices. Prior |
| to this change radio devices would identify solely by having exactly one |
| tuner whose type field reads <constant>V4L2_TUNER_RADIO</constant>.</para> |
| </listitem> |
| |
| <listitem> |
| <para>An optional driver access priority mechanism was |
| added, see <xref linkend="app-pri" /> for details.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The audio input and output interface was found to be |
| incomplete.</para> |
| <para>Previously the &VIDIOC-G-AUDIO; |
| ioctl would enumerate the available audio inputs. An ioctl to |
| determine the current audio input, if more than one combines with the |
| current video input, did not exist. So |
| <constant>VIDIOC_G_AUDIO</constant> was renamed to |
| <constant>VIDIOC_G_AUDIO_OLD</constant>, this ioctl will be removed in |
| the future. The &VIDIOC-ENUMAUDIO; ioctl was added to enumerate |
| audio inputs, while &VIDIOC-G-AUDIO; now reports the current audio |
| input.</para> |
| <para>The same changes were made to &VIDIOC-G-AUDOUT; and |
| &VIDIOC-ENUMAUDOUT;.</para> |
| <para>Until further the "videodev" module will automatically |
| translate between the old and new ioctls, but drivers and applications |
| must be updated to successfully compile again.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &VIDIOC-OVERLAY; ioctl was incorrectly defined with |
| write-read parameter. It was changed to write-only, while the write-read |
| version was renamed to <constant>VIDIOC_OVERLAY_OLD</constant>. The old |
| ioctl will be removed in the future. Until further the "videodev" |
| kernel module will automatically translate to the new version, so drivers |
| must be recompiled, but not applications.</para> |
| </listitem> |
| |
| <listitem> |
| <para><xref linkend="overlay" /> incorrectly stated that |
| clipping rectangles define regions where the video can be seen. |
| Correct is that clipping rectangles define regions where |
| <emphasis>no</emphasis> video shall be displayed and so the graphics |
| surface can be seen.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The &VIDIOC-S-PARM; and &VIDIOC-S-CTRL; ioctls were |
| defined with write-only parameter, inconsistent with other ioctls |
| modifying their argument. They were changed to write-read, while a |
| <constant>_OLD</constant> suffix was added to the write-only versions. |
| The old ioctls will be removed in the future. Drivers and |
| applications assuming a constant parameter need an update.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 2003-11-05</title> |
| <orderedlist> |
| <listitem> |
| <para>In <xref linkend="pixfmt-rgb" /> the following pixel |
| formats were incorrectly transferred from Bill Dirks' V4L2 |
| specification. Descriptions below refer to bytes in memory, in |
| ascending address order.<informaltable> |
| <tgroup cols="3"> |
| <thead> |
| <row> |
| <entry>Symbol</entry> |
| <entry>In this document prior to revision |
| 0.5</entry> |
| <entry>Corrected</entry> |
| </row> |
| </thead> |
| <tbody valign="top"> |
| <row> |
| <entry><constant>V4L2_PIX_FMT_RGB24</constant></entry> |
| <entry>B, G, R</entry> |
| <entry>R, G, B</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_PIX_FMT_BGR24</constant></entry> |
| <entry>R, G, B</entry> |
| <entry>B, G, R</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_PIX_FMT_RGB32</constant></entry> |
| <entry>B, G, R, X</entry> |
| <entry>R, G, B, X</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_PIX_FMT_BGR32</constant></entry> |
| <entry>R, G, B, X</entry> |
| <entry>B, G, R, X</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> The |
| <constant>V4L2_PIX_FMT_BGR24</constant> example was always |
| correct.</para> |
| <para>In <xref linkend="v4l-image-properties" /> the mapping |
| of the V4L <constant>VIDEO_PALETTE_RGB24</constant> and |
| <constant>VIDEO_PALETTE_RGB32</constant> formats to V4L2 pixel formats |
| was accordingly corrected.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Unrelated to the fixes above, drivers may still |
| interpret some V4L2 RGB pixel formats differently. These issues have |
| yet to be addressed, for details see <xref |
| linkend="pixfmt-rgb" />.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.6, 2004-05-09</title> |
| <orderedlist> |
| <listitem> |
| <para>The &VIDIOC-CROPCAP; ioctl was incorrectly defined |
| with read-only parameter. It is now defined as write-read ioctl, while |
| the read-only version was renamed to |
| <constant>VIDIOC_CROPCAP_OLD</constant>. The old ioctl will be removed |
| in the future.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.8</title> |
| <orderedlist> |
| <listitem> |
| <para>A new field <structfield>input</structfield> (former |
| <structfield>reserved[0]</structfield>) was added to the &v4l2-buffer; |
| structure. Purpose of this field is to alternate between video inputs |
| (⪚ cameras) in step with the video capturing process. This function |
| must be enabled with the new <constant>V4L2_BUF_FLAG_INPUT</constant> |
| flag. The <structfield>flags</structfield> field is no longer |
| read-only.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2004-08-01</title> |
| |
| <orderedlist> |
| <listitem> |
| <para>The return value of the |
| <xref linkend="func-open" /> function was incorrectly documented.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Audio output ioctls end in -AUDOUT, not -AUDIOOUT.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In the Current Audio Input example the |
| <constant>VIDIOC_G_AUDIO</constant> ioctl took the wrong |
| argument.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The documentation of the &VIDIOC-QBUF; and |
| &VIDIOC-DQBUF; ioctls did not mention the &v4l2-buffer; |
| <structfield>memory</structfield> field. It was also missing from |
| examples. Also on the <constant>VIDIOC_DQBUF</constant> page the &EIO; |
| was not documented.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.14</title> |
| <orderedlist> |
| <listitem> |
| <para>A new sliced VBI interface was added. It is documented |
| in <xref linkend="sliced" /> and replaces the interface first |
| proposed in V4L2 specification 0.8.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.15</title> |
| <orderedlist> |
| <listitem> |
| <para>The &VIDIOC-LOG-STATUS; ioctl was added.</para> |
| </listitem> |
| |
| <listitem> |
| <para>New video standards |
| <constant>V4L2_STD_NTSC_443</constant>, |
| <constant>V4L2_STD_SECAM_LC</constant>, |
| <constant>V4L2_STD_SECAM_DK</constant> (a set of SECAM D, K and K1), |
| and <constant>V4L2_STD_ATSC</constant> (a set of |
| <constant>V4L2_STD_ATSC_8_VSB</constant> and |
| <constant>V4L2_STD_ATSC_16_VSB</constant>) were defined. Note the |
| <constant>V4L2_STD_525_60</constant> set now includes |
| <constant>V4L2_STD_NTSC_443</constant>. See also <xref |
| linkend="v4l2-std-id" />.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The <constant>VIDIOC_G_COMP</constant> and |
| <constant>VIDIOC_S_COMP</constant> ioctl were renamed to |
| <constant>VIDIOC_G_MPEGCOMP</constant> and |
| <constant>VIDIOC_S_MPEGCOMP</constant> respectively. Their argument |
| was replaced by a struct |
| <structname>v4l2_mpeg_compression</structname> pointer. (The |
| <constant>VIDIOC_G_MPEGCOMP</constant> and |
| <constant>VIDIOC_S_MPEGCOMP</constant> ioctls where removed in Linux |
| 2.6.25.)</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2005-11-27</title> |
| <para>The capture example in <xref linkend="capture-example" /> |
| called the &VIDIOC-S-CROP; ioctl without checking if cropping is |
| supported. In the video standard selection example in |
| <xref linkend="standard" /> the &VIDIOC-S-STD; call used the wrong |
| argument type.</para> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2006-01-10</title> |
| <orderedlist> |
| <listitem> |
| <para>The <constant>V4L2_IN_ST_COLOR_KILL</constant> flag in |
| &v4l2-input; not only indicates if the color killer is enabled, but |
| also if it is active. (The color killer disables color decoding when |
| it detects no color in the video signal to improve the image |
| quality.)</para> |
| </listitem> |
| |
| <listitem> |
| <para>&VIDIOC-S-PARM; is a write-read ioctl, not write-only as |
| stated on its reference page. The ioctl changed in 2003 as noted above.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2006-02-03</title> |
| <orderedlist> |
| <listitem> |
| <para>In &v4l2-captureparm; and &v4l2-outputparm; the |
| <structfield>timeperframe</structfield> field gives the time in |
| seconds, not microseconds.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2006-02-04</title> |
| <orderedlist> |
| <listitem> |
| <para>The <structfield>clips</structfield> field in |
| &v4l2-window; must point to an array of &v4l2-clip;, not a linked |
| list, because drivers ignore the struct |
| <structname>v4l2_clip</structname>.<structfield>next</structfield> |
| pointer.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.17</title> |
| <orderedlist> |
| <listitem> |
| <para>New video standard macros were added: |
| <constant>V4L2_STD_NTSC_M_KR</constant> (NTSC M South Korea), and the |
| sets <constant>V4L2_STD_MN</constant>, |
| <constant>V4L2_STD_B</constant>, <constant>V4L2_STD_GH</constant> and |
| <constant>V4L2_STD_DK</constant>. The |
| <constant>V4L2_STD_NTSC</constant> and |
| <constant>V4L2_STD_SECAM</constant> sets now include |
| <constant>V4L2_STD_NTSC_M_KR</constant> and |
| <constant>V4L2_STD_SECAM_LC</constant> respectively.</para> |
| </listitem> |
| |
| <listitem> |
| <para>A new <constant>V4L2_TUNER_MODE_LANG1_LANG2</constant> |
| was defined to record both languages of a bilingual program. The |
| use of <constant>V4L2_TUNER_MODE_STEREO</constant> for this purpose |
| is deprecated now. See the &VIDIOC-G-TUNER; section for |
| details.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2006-09-23 (Draft 0.15)</title> |
| <orderedlist> |
| <listitem> |
| <para>In various places |
| <constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant> and |
| <constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant> of the sliced VBI |
| interface were not mentioned along with other buffer types.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In <xref linkend="vidioc-g-audio" /> it was clarified |
| that the &v4l2-audio; <structfield>mode</structfield> field is a flags |
| field.</para> |
| </listitem> |
| |
| <listitem> |
| <para><xref linkend="vidioc-querycap" /> did not mention the |
| sliced VBI and radio capability flags.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In <xref linkend="vidioc-g-frequency" /> it was |
| clarified that applications must initialize the tuner |
| <structfield>type</structfield> field of &v4l2-frequency; before |
| calling &VIDIOC-S-FREQUENCY;.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The <structfield>reserved</structfield> array |
| in &v4l2-requestbuffers; has 2 elements, not 32.</para> |
| </listitem> |
| |
| <listitem> |
| <para>In <xref linkend="output" /> and <xref |
| linkend="raw-vbi" /> the device file names |
| <filename>/dev/vout</filename> which never caught on were replaced |
| by <filename>/dev/video</filename>.</para> |
| </listitem> |
| |
| <listitem> |
| <para>With Linux 2.6.15 the possible range for VBI device minor |
| numbers was extended from 224-239 to 224-255. Accordingly device file names |
| <filename>/dev/vbi0</filename> to <filename>/dev/vbi31</filename> are |
| possible now.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.18</title> |
| <orderedlist> |
| <listitem> |
| <para>New ioctls &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; |
| and &VIDIOC-TRY-EXT-CTRLS; were added, a flag to skip unsupported |
| controls with &VIDIOC-QUERYCTRL;, new control types |
| <constant>V4L2_CTRL_TYPE_INTEGER64</constant> and |
| <constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant> (<xref |
| linkend="v4l2-ctrl-type" />), and new control flags |
| <constant>V4L2_CTRL_FLAG_READ_ONLY</constant>, |
| <constant>V4L2_CTRL_FLAG_UPDATE</constant>, |
| <constant>V4L2_CTRL_FLAG_INACTIVE</constant> and |
| <constant>V4L2_CTRL_FLAG_SLIDER</constant> (<xref |
| linkend="control-flags" />). See <xref |
| linkend="extended-controls" /> for details.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.19</title> |
| <orderedlist> |
| <listitem> |
| <para>In &v4l2-sliced-vbi-cap; a buffer type field was added |
| replacing a reserved field. Note on architectures where the size of |
| enum types differs from int types the size of the structure changed. |
| The &VIDIOC-G-SLICED-VBI-CAP; ioctl was redefined from being read-only |
| to write-read. Applications must initialize the type field and clear |
| the reserved fields now. These changes may <emphasis>break the |
| compatibility</emphasis> with older drivers and applications.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The ioctls &VIDIOC-ENUM-FRAMESIZES; and |
| &VIDIOC-ENUM-FRAMEINTERVALS; were added.</para> |
| </listitem> |
| |
| <listitem> |
| <para>A new pixel format <constant>V4L2_PIX_FMT_RGB444</constant> (<xref |
| linkend="rgb-formats" />) was added.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 spec erratum 2006-10-12 (Draft 0.17)</title> |
| <orderedlist> |
| <listitem> |
| <para><constant>V4L2_PIX_FMT_HM12</constant> (<xref |
| linkend="reserved-formats" />) is a YUV 4:2:0, not 4:2:2 format.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.21</title> |
| <orderedlist> |
| <listitem> |
| <para>The <filename>videodev2.h</filename> header file is |
| now dual licensed under GNU General Public License version two or |
| later, and under a 3-clause BSD-style license.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.22</title> |
| <orderedlist> |
| <listitem> |
| <para>Two new field orders |
| <constant>V4L2_FIELD_INTERLACED_TB</constant> and |
| <constant>V4L2_FIELD_INTERLACED_BT</constant> were |
| added. See <xref linkend="v4l2-field" /> for details.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Three new clipping/blending methods with a global or |
| straight or inverted local alpha value were added to the video overlay |
| interface. See the description of the &VIDIOC-G-FBUF; and |
| &VIDIOC-S-FBUF; ioctls for details.</para> |
| <para>A new <structfield>global_alpha</structfield> field |
| was added to <link |
| linkend="v4l2-window"><structname>v4l2_window</structname></link>, |
| extending the structure. This may <emphasis>break |
| compatibility</emphasis> with applications using a struct |
| <structname>v4l2_window</structname> directly. However the <link |
| linkend="vidioc-g-fmt">VIDIOC_G/S/TRY_FMT</link> ioctls, which take a |
| pointer to a <link linkend="v4l2-format">v4l2_format</link> parent |
| structure with padding bytes at the end, are not affected.</para> |
| </listitem> |
| |
| <listitem> |
| <para>The format of the <structfield>chromakey</structfield> |
| field in &v4l2-window; changed from "host order RGB32" to a pixel |
| value in the same format as the framebuffer. This may <emphasis>break |
| compatibility</emphasis> with existing applications. Drivers |
| supporting the "host order RGB32" format are not known.</para> |
| </listitem> |
| |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.24</title> |
| <orderedlist> |
| <listitem> |
| <para>The pixel formats |
| <constant>V4L2_PIX_FMT_PAL8</constant>, |
| <constant>V4L2_PIX_FMT_YUV444</constant>, |
| <constant>V4L2_PIX_FMT_YUV555</constant>, |
| <constant>V4L2_PIX_FMT_YUV565</constant> and |
| <constant>V4L2_PIX_FMT_YUV32</constant> were added.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.25</title> |
| <orderedlist> |
| <listitem> |
| <para>The pixel formats <link linkend="V4L2-PIX-FMT-Y16"> |
| <constant>V4L2_PIX_FMT_Y16</constant></link> and <link |
| linkend="V4L2-PIX-FMT-SBGGR16"> |
| <constant>V4L2_PIX_FMT_SBGGR16</constant></link> were added.</para> |
| </listitem> |
| <listitem> |
| <para>New <link linkend="control">controls</link> |
| <constant>V4L2_CID_POWER_LINE_FREQUENCY</constant>, |
| <constant>V4L2_CID_HUE_AUTO</constant>, |
| <constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant>, |
| <constant>V4L2_CID_SHARPNESS</constant> and |
| <constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant> were added. The |
| controls <constant>V4L2_CID_BLACK_LEVEL</constant>, |
| <constant>V4L2_CID_WHITENESS</constant>, |
| <constant>V4L2_CID_HCENTER</constant> and |
| <constant>V4L2_CID_VCENTER</constant> were deprecated. |
| </para> |
| </listitem> |
| <listitem> |
| <para>A <link linkend="camera-controls">Camera controls |
| class</link> was added, with the new controls |
| <constant>V4L2_CID_EXPOSURE_AUTO</constant>, |
| <constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>, |
| <constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>, |
| <constant>V4L2_CID_PAN_RELATIVE</constant>, |
| <constant>V4L2_CID_TILT_RELATIVE</constant>, |
| <constant>V4L2_CID_PAN_RESET</constant>, |
| <constant>V4L2_CID_TILT_RESET</constant>, |
| <constant>V4L2_CID_PAN_ABSOLUTE</constant>, |
| <constant>V4L2_CID_TILT_ABSOLUTE</constant>, |
| <constant>V4L2_CID_FOCUS_ABSOLUTE</constant>, |
| <constant>V4L2_CID_FOCUS_RELATIVE</constant> and |
| <constant>V4L2_CID_FOCUS_AUTO</constant>.</para> |
| </listitem> |
| <listitem> |
| <para>The <constant>VIDIOC_G_MPEGCOMP</constant> and |
| <constant>VIDIOC_S_MPEGCOMP</constant> ioctls, which were superseded |
| by the <link linkend="extended-controls">extended controls</link> |
| interface in Linux 2.6.18, where finally removed from the |
| <filename>videodev2.h</filename> header file.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.26</title> |
| <orderedlist> |
| <listitem> |
| <para>The pixel formats |
| <constant>V4L2_PIX_FMT_Y16</constant> and |
| <constant>V4L2_PIX_FMT_SBGGR16</constant> were added.</para> |
| </listitem> |
| <listitem> |
| <para>Added user controls |
| <constant>V4L2_CID_CHROMA_AGC</constant> and |
| <constant>V4L2_CID_COLOR_KILLER</constant>.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.27</title> |
| <orderedlist> |
| <listitem> |
| <para>The &VIDIOC-S-HW-FREQ-SEEK; ioctl and the |
| <constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability were added.</para> |
| </listitem> |
| <listitem> |
| <para>The pixel formats |
| <constant>V4L2_PIX_FMT_YVYU</constant>, |
| <constant>V4L2_PIX_FMT_PCA501</constant>, |
| <constant>V4L2_PIX_FMT_PCA505</constant>, |
| <constant>V4L2_PIX_FMT_PCA508</constant>, |
| <constant>V4L2_PIX_FMT_PCA561</constant>, |
| <constant>V4L2_PIX_FMT_SGBRG8</constant>, |
| <constant>V4L2_PIX_FMT_PAC207</constant> and |
| <constant>V4L2_PIX_FMT_PJPG</constant> were added.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.28</title> |
| <orderedlist> |
| <listitem> |
| <para>Added <constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant> and |
| <constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant> MPEG audio encodings.</para> |
| </listitem> |
| <listitem> |
| <para>Added <constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant> MPEG |
| video encoding.</para> |
| </listitem> |
| <listitem> |
| <para>The pixel formats |
| <constant>V4L2_PIX_FMT_SGRBG10</constant> and |
| <constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant> were added.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section> |
| <title>V4L2 in Linux 2.6.29</title> |
| <orderedlist> |
| <listitem> |
| <para>The <constant>VIDIOC_G_CHIP_IDENT</constant> ioctl was renamed |
| to <constant>VIDIOC_G_CHIP_IDENT_OLD</constant> and &VIDIOC-DBG-G-CHIP-IDENT; |
| was introduced in its place. The old struct <structname>v4l2_chip_ident</structname> |
| was renamed to <structname id="v4l2-chip-ident-old">v4l2_chip_ident_old</structname>.</para> |
| </listitem> |
| <listitem> |
| <para>The pixel formats |
| <constant>V4L2_PIX_FMT_VYUY</constant>, |
| <constant>V4L2_PIX_FMT_NV16</constant> and |
| <constant>V4L2_PIX_FMT_NV61</constant> were added.</para> |
| </listitem> |
| <listitem> |
| <para>Added camera controls |
| <constant>V4L2_CID_ZOOM_ABSOLUTE</constant>, |
| <constant>V4L2_CID_ZOOM_RELATIVE</constant>, |
| <constant>V4L2_CID_ZOOM_CONTINUOUS</constant> and |
| <constant>V4L2_CID_PRIVACY</constant>.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| <section> |
| <title>V4L2 in Linux 2.6.30</title> |
| <orderedlist> |
| <listitem> |
| <para>New control flag <constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant> was added.</para> |
| </listitem> |
| <listitem> |
| <para>New control <constant>V4L2_CID_COLORFX</constant> was added.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| <section> |
| <title>V4L2 in Linux 2.6.32</title> |
| <orderedlist> |
| <listitem> |
| <para>In order to be easier to compare a V4L2 API and a kernel |
| version, now V4L2 API is numbered using the Linux Kernel version numeration.</para> |
| </listitem> |
| <listitem> |
| <para>Finalized the RDS capture API. See <xref linkend="rds" /> for |
| more information.</para> |
| </listitem> |
| <listitem> |
| <para>Added new capabilities for modulators and RDS encoders.</para> |
| </listitem> |
| <listitem> |
| <para>Add description for libv4l API.</para> |
| </listitem> |
| <listitem> |
| <para>Added support for string controls via new type <constant>V4L2_CTRL_TYPE_STRING</constant>.</para> |
| </listitem> |
| <listitem> |
| <para>Added <constant>V4L2_CID_BAND_STOP_FILTER</constant> documentation.</para> |
| </listitem> |
| <listitem> |
| <para>Added FM Modulator (FM TX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_TX</constant> and their Control IDs.</para> |
| </listitem> |
| <listitem> |
| <para>Added Remote Controller chapter, describing the default Remote Controller mapping for media devices.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| <section> |
| <title>V4L2 in Linux 2.6.33</title> |
| <orderedlist> |
| <listitem> |
| <para>Added support for Digital Video timings in order to support HDTV receivers and transmitters.</para> |
| </listitem> |
| </orderedlist> |
| </section> |
| <section> |
| <title>V4L2 in Linux 2.6.34</title> |
| <orderedlist> |
| <listitem> |
| <para>Added |
| <constant>V4L2_CID_IRIS_ABSOLUTE</constant> and |
| <constant>V4L2_CID_IRIS_RELATIVE</constant> controls to the |
| <link linkend="camera-controls">Camera controls class</link>. |
| </para> |
| </listitem> |
| </orderedlist> |
| </section> |
| |
| <section id="other"> |
| <title>Relation of V4L2 to other Linux multimedia APIs</title> |
| |
| <section id="xvideo"> |
| <title>X Video Extension</title> |
| |
| <para>The X Video Extension (abbreviated XVideo or just Xv) is |
| an extension of the X Window system, implemented for example by the |
| XFree86 project. Its scope is similar to V4L2, an API to video capture |
| and output devices for X clients. Xv allows applications to display |
| live video in a window, send window contents to a TV output, and |
| capture or output still images in XPixmaps<footnote> |
| <para>This is not implemented in XFree86.</para> |
| </footnote>. With their implementation XFree86 makes the |
| extension available across many operating systems and |
| architectures.</para> |
| |
| <para>Because the driver is embedded into the X server Xv has a |
| number of advantages over the V4L2 <link linkend="overlay">video |
| overlay interface</link>. The driver can easily determine the overlay |
| target, &ie; visible graphics memory or off-screen buffers for a |
| destructive overlay. It can program the RAMDAC for a non-destructive |
| overlay, scaling or color-keying, or the clipping functions of the |
| video capture hardware, always in sync with drawing operations or |
| windows moving or changing their stacking order.</para> |
| |
| <para>To combine the advantages of Xv and V4L a special Xv |
| driver exists in XFree86 and XOrg, just programming any overlay capable |
| Video4Linux device it finds. To enable it |
| <filename>/etc/X11/XF86Config</filename> must contain these lines:</para> |
| <para><screen> |
| Section "Module" |
| Load "v4l" |
| EndSection</screen></para> |
| |
| <para>As of XFree86 4.2 this driver still supports only V4L |
| ioctls, however it should work just fine with all V4L2 devices through |
| the V4L2 backward-compatibility layer. Since V4L2 permits multiple |
| opens it is possible (if supported by the V4L2 driver) to capture |
| video while an X client requested video overlay. Restrictions of |
| simultaneous capturing and overlay are discussed in <xref |
| linkend="overlay" /> apply.</para> |
| |
| <para>Only marginally related to V4L2, XFree86 extended Xv to |
| support hardware YUV to RGB conversion and scaling for faster video |
| playback, and added an interface to MPEG-2 decoding hardware. This API |
| is useful to display images captured with V4L2 devices.</para> |
| </section> |
| |
| <section> |
| <title>Digital Video</title> |
| |
| <para>V4L2 does not support digital terrestrial, cable or |
| satellite broadcast. A separate project aiming at digital receivers |
| exists. You can find its homepage at <ulink |
| url="http://linuxtv.org">http://linuxtv.org</ulink>. The Linux DVB API |
| has no connection to the V4L2 API except that drivers for hybrid |
| hardware may support both.</para> |
| </section> |
| |
| <section> |
| <title>Audio Interfaces</title> |
| |
| <para>[to do - OSS/ALSA]</para> |
| </section> |
| </section> |
| |
| <section id="experimental"> |
| <title>Experimental API Elements</title> |
| |
| <para>The following V4L2 API elements are currently experimental |
| and may change in the future.</para> |
| |
| <itemizedlist> |
| <listitem> |
| <para>Video Output Overlay (OSD) Interface, <xref |
| linkend="osd" />.</para> |
| </listitem> |
| <listitem> |
| <para><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant>, |
| &v4l2-buf-type;, <xref linkend="v4l2-buf-type" />.</para> |
| </listitem> |
| <listitem> |
| <para><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant>, |
| &VIDIOC-QUERYCAP; ioctl, <xref linkend="device-capabilities" />.</para> |
| </listitem> |
| <listitem> |
| <para>&VIDIOC-ENUM-FRAMESIZES; and |
| &VIDIOC-ENUM-FRAMEINTERVALS; ioctls.</para> |
| </listitem> |
| <listitem> |
| <para>&VIDIOC-G-ENC-INDEX; ioctl.</para> |
| </listitem> |
| <listitem> |
| <para>&VIDIOC-ENCODER-CMD; and &VIDIOC-TRY-ENCODER-CMD; |
| ioctls.</para> |
| </listitem> |
| <listitem> |
| <para>&VIDIOC-DBG-G-REGISTER; and &VIDIOC-DBG-S-REGISTER; |
| ioctls.</para> |
| </listitem> |
| <listitem> |
| <para>&VIDIOC-DBG-G-CHIP-IDENT; ioctl.</para> |
| </listitem> |
| </itemizedlist> |
| </section> |
| |
| <section id="obsolete"> |
| <title>Obsolete API Elements</title> |
| |
| <para>The following V4L2 API elements were superseded by new |
| interfaces and should not be implemented in new drivers.</para> |
| |
| <itemizedlist> |
| <listitem> |
| <para><constant>VIDIOC_G_MPEGCOMP</constant> and |
| <constant>VIDIOC_S_MPEGCOMP</constant> ioctls. Use Extended Controls, |
| <xref linkend="extended-controls" />.</para> |
| </listitem> |
| </itemizedlist> |
| </section> |
| |
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