| |
| SN9C10x PC Camera Controllers |
| Driver for Linux |
| ============================= |
| |
| - Documentation - |
| |
| |
| Index |
| ===== |
| 1. Copyright |
| 2. Disclaimer |
| 3. License |
| 4. Overview and features |
| 5. Module dependencies |
| 6. Module loading |
| 7. Module parameters |
| 8. Optional device control through "sysfs" |
| 9. Supported devices |
| 10. Notes for V4L2 application developers |
| 11. Video frame formats |
| 12. Contact information |
| 13. Credits |
| |
| |
| 1. Copyright |
| ============ |
| Copyright (C) 2004-2006 by Luca Risolia <luca.risolia@studio.unibo.it> |
| |
| |
| 2. Disclaimer |
| ============= |
| SONiX is a trademark of SONiX Technology Company Limited, inc. |
| This software is not sponsored or developed by SONiX. |
| |
| |
| 3. License |
| ========== |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, write to the Free Software |
| Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| |
| |
| 4. Overview and features |
| ======================== |
| This driver attempts to support the video interface of the devices mounting the |
| SONiX SN9C101, SN9C102 and SN9C103 PC Camera Controllers. |
| |
| It's worth to note that SONiX has never collaborated with the author during the |
| development of this project, despite several requests for enough detailed |
| specifications of the register tables, compression engine and video data format |
| of the above chips. Nevertheless, these informations are no longer necessary, |
| becouse all the aspects related to these chips are known and have been |
| described in detail in this documentation. |
| |
| The driver relies on the Video4Linux2 and USB core modules. It has been |
| designed to run properly on SMP systems as well. |
| |
| The latest version of the SN9C10x driver can be found at the following URL: |
| http://www.linux-projects.org/ |
| |
| Some of the features of the driver are: |
| |
| - full compliance with the Video4Linux2 API (see also "Notes for V4L2 |
| application developers" paragraph); |
| - available mmap or read/poll methods for video streaming through isochronous |
| data transfers; |
| - automatic detection of image sensor; |
| - support for built-in microphone interface; |
| - support for any window resolutions and optional panning within the maximum |
| pixel area of image sensor; |
| - image downscaling with arbitrary scaling factors from 1, 2 and 4 in both |
| directions (see "Notes for V4L2 application developers" paragraph); |
| - two different video formats for uncompressed or compressed data in low or |
| high compression quality (see also "Notes for V4L2 application developers" |
| and "Video frame formats" paragraphs); |
| - full support for the capabilities of many of the possible image sensors that |
| can be connected to the SN9C10x bridges, including, for istance, red, green, |
| blue and global gain adjustments and exposure (see "Supported devices" |
| paragraph for details); |
| - use of default color settings for sunlight conditions; |
| - dynamic I/O interface for both SN9C10x and image sensor control and |
| monitoring (see "Optional device control through 'sysfs'" paragraph); |
| - dynamic driver control thanks to various module parameters (see "Module |
| parameters" paragraph); |
| - up to 64 cameras can be handled at the same time; they can be connected and |
| disconnected from the host many times without turning off the computer, if |
| the system supports hotplugging; |
| - no known bugs. |
| |
| |
| 5. Module dependencies |
| ====================== |
| For it to work properly, the driver needs kernel support for Video4Linux and |
| USB. |
| |
| The following options of the kernel configuration file must be enabled and |
| corresponding modules must be compiled: |
| |
| # Multimedia devices |
| # |
| CONFIG_VIDEO_DEV=m |
| |
| To enable advanced debugging functionality on the device through /sysfs: |
| |
| # Multimedia devices |
| # |
| CONFIG_VIDEO_ADV_DEBUG=y |
| |
| # USB support |
| # |
| CONFIG_USB=m |
| |
| In addition, depending on the hardware being used, the modules below are |
| necessary: |
| |
| # USB Host Controller Drivers |
| # |
| CONFIG_USB_EHCI_HCD=m |
| CONFIG_USB_UHCI_HCD=m |
| CONFIG_USB_OHCI_HCD=m |
| |
| The SN9C103 controller also provides a built-in microphone interface. It is |
| supported by the USB Audio driver thanks to the ALSA API: |
| |
| # Sound |
| # |
| CONFIG_SOUND=y |
| |
| # Advanced Linux Sound Architecture |
| # |
| CONFIG_SND=m |
| |
| # USB devices |
| # |
| CONFIG_SND_USB_AUDIO=m |
| |
| And finally: |
| |
| # USB Multimedia devices |
| # |
| CONFIG_USB_SN9C102=m |
| |
| |
| 6. Module loading |
| ================= |
| To use the driver, it is necessary to load the "sn9c102" module into memory |
| after every other module required: "videodev", "usbcore" and, depending on |
| the USB host controller you have, "ehci-hcd", "uhci-hcd" or "ohci-hcd". |
| |
| Loading can be done as shown below: |
| |
| [root@localhost home]# modprobe sn9c102 |
| |
| At this point the devices should be recognized. You can invoke "dmesg" to |
| analyze kernel messages and verify that the loading process has gone well: |
| |
| [user@localhost home]$ dmesg |
| |
| |
| 7. Module parameters |
| ==================== |
| Module parameters are listed below: |
| ------------------------------------------------------------------------------- |
| Name: video_nr |
| Type: short array (min = 0, max = 64) |
| Syntax: <-1|n[,...]> |
| Description: Specify V4L2 minor mode number: |
| -1 = use next available |
| n = use minor number n |
| You can specify up to 64 cameras this way. |
| For example: |
| video_nr=-1,2,-1 would assign minor number 2 to the second |
| recognized camera and use auto for the first one and for every |
| other camera. |
| Default: -1 |
| ------------------------------------------------------------------------------- |
| Name: force_munmap |
| Type: bool array (min = 0, max = 64) |
| Syntax: <0|1[,...]> |
| Description: Force the application to unmap previously mapped buffer memory |
| before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not |
| all the applications support this feature. This parameter is |
| specific for each detected camera. |
| 0 = do not force memory unmapping |
| 1 = force memory unmapping (save memory) |
| Default: 0 |
| ------------------------------------------------------------------------------- |
| Name: frame_timeout |
| Type: uint array (min = 0, max = 64) |
| Syntax: <n[,...]> |
| Description: Timeout for a video frame in seconds. This parameter is |
| specific for each detected camera. This parameter can be |
| changed at runtime thanks to the /sys filesystem interface. |
| Default: 2 |
| ------------------------------------------------------------------------------- |
| Name: debug |
| Type: ushort |
| Syntax: <n> |
| Description: Debugging information level, from 0 to 3: |
| 0 = none (use carefully) |
| 1 = critical errors |
| 2 = significant informations |
| 3 = more verbose messages |
| Level 3 is useful for testing only, when only one device |
| is used. It also shows some more informations about the |
| hardware being detected. This parameter can be changed at |
| runtime thanks to the /sys filesystem interface. |
| Default: 2 |
| ------------------------------------------------------------------------------- |
| |
| |
| 8. Optional device control through "sysfs" [1] |
| ========================================== |
| If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled, |
| it is possible to read and write both the SN9C10x and the image sensor |
| registers by using the "sysfs" filesystem interface. |
| |
| Every time a supported device is recognized, a write-only file named "green" is |
| created in the /sys/class/video4linux/videoX directory. You can set the green |
| channel's gain by writing the desired value to it. The value may range from 0 |
| to 15 for SN9C101 or SN9C102 bridges, from 0 to 127 for SN9C103 bridges. |
| Similarly, only for SN9C103 controllers, blue and red gain control files are |
| available in the same directory, for which accepted values may range from 0 to |
| 127. |
| |
| There are other four entries in the directory above for each registered camera: |
| "reg", "val", "i2c_reg" and "i2c_val". The first two files control the |
| SN9C10x bridge, while the other two control the sensor chip. "reg" and |
| "i2c_reg" hold the values of the current register index where the following |
| reading/writing operations are addressed at through "val" and "i2c_val". Their |
| use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not |
| be created if the sensor does not actually support the standard I2C protocol or |
| its registers are not 8-bit long. Also, remember that you must be logged in as |
| root before writing to them. |
| |
| As an example, suppose we were to want to read the value contained in the |
| register number 1 of the sensor register table - which is usually the product |
| identifier - of the camera registered as "/dev/video0": |
| |
| [root@localhost #] cd /sys/class/video4linux/video0 |
| [root@localhost #] echo 1 > i2c_reg |
| [root@localhost #] cat i2c_val |
| |
| Note that "cat" will fail if sensor registers cannot be read. |
| |
| Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2: |
| |
| [root@localhost #] echo 0x11 > reg |
| [root@localhost #] echo 2 > val |
| |
| Note that the SN9C10x always returns 0 when some of its registers are read. |
| To avoid race conditions, all the I/O accesses to the above files are |
| serialized. |
| |
| The sysfs interface also provides the "frame_header" entry, which exports the |
| frame header of the most recent requested and captured video frame. The header |
| is always 18-bytes long and is appended to every video frame by the SN9C10x |
| controllers. As an example, this additional information can be used by the user |
| application for implementing auto-exposure features via software. |
| |
| The following table describes the frame header: |
| |
| Byte # Value Description |
| ------ ----- ----------- |
| 0x00 0xFF Frame synchronisation pattern. |
| 0x01 0xFF Frame synchronisation pattern. |
| 0x02 0x00 Frame synchronisation pattern. |
| 0x03 0xC4 Frame synchronisation pattern. |
| 0x04 0xC4 Frame synchronisation pattern. |
| 0x05 0x96 Frame synchronisation pattern. |
| 0x06 0xXX Unknown meaning. The exact value depends on the chip; |
| possible values are 0x00, 0x01 and 0x20. |
| 0x07 0xXX Variable value, whose bits are ff00uzzc, where ff is a |
| frame counter, u is unknown, zz is a size indicator |
| (00 = VGA, 01 = SIF, 10 = QSIF) and c stands for |
| "compression enabled" (1 = yes, 0 = no). |
| 0x08 0xXX Brightness sum inside Auto-Exposure area (low-byte). |
| 0x09 0xXX Brightness sum inside Auto-Exposure area (high-byte). |
| For a pure white image, this number will be equal to 500 |
| times the area of the specified AE area. For images |
| that are not pure white, the value scales down according |
| to relative whiteness. |
| 0x0A 0xXX Brightness sum outside Auto-Exposure area (low-byte). |
| 0x0B 0xXX Brightness sum outside Auto-Exposure area (high-byte). |
| For a pure white image, this number will be equal to 125 |
| times the area outside of the specified AE area. For |
| images that are not pure white, the value scales down |
| according to relative whiteness. |
| according to relative whiteness. |
| |
| The following bytes are used by the SN9C103 bridge only: |
| |
| 0x0C 0xXX Unknown meaning |
| 0x0D 0xXX Unknown meaning |
| 0x0E 0xXX Unknown meaning |
| 0x0F 0xXX Unknown meaning |
| 0x10 0xXX Unknown meaning |
| 0x11 0xXX Unknown meaning |
| |
| The AE area (sx, sy, ex, ey) in the active window can be set by programming the |
| registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C10x controllers, where one unit |
| corresponds to 32 pixels. |
| |
| [1] Part of the meaning of the frame header has been documented by Bertrik |
| Sikken. |
| |
| |
| 9. Supported devices |
| ==================== |
| None of the names of the companies as well as their products will be mentioned |
| here. They have never collaborated with the author, so no advertising. |
| |
| From the point of view of a driver, what unambiguously identify a device are |
| its vendor and product USB identifiers. Below is a list of known identifiers of |
| devices mounting the SN9C10x PC camera controllers: |
| |
| Vendor ID Product ID |
| --------- ---------- |
| 0x0c45 0x6001 |
| 0x0c45 0x6005 |
| 0x0c45 0x6007 |
| 0x0c45 0x6009 |
| 0x0c45 0x600d |
| 0x0c45 0x6024 |
| 0x0c45 0x6025 |
| 0x0c45 0x6028 |
| 0x0c45 0x6029 |
| 0x0c45 0x602a |
| 0x0c45 0x602b |
| 0x0c45 0x602c |
| 0x0c45 0x602d |
| 0x0c45 0x602e |
| 0x0c45 0x6030 |
| 0x0c45 0x6080 |
| 0x0c45 0x6082 |
| 0x0c45 0x6083 |
| 0x0c45 0x6088 |
| 0x0c45 0x608a |
| 0x0c45 0x608b |
| 0x0c45 0x608c |
| 0x0c45 0x608e |
| 0x0c45 0x608f |
| 0x0c45 0x60a0 |
| 0x0c45 0x60a2 |
| 0x0c45 0x60a3 |
| 0x0c45 0x60a8 |
| 0x0c45 0x60aa |
| 0x0c45 0x60ab |
| 0x0c45 0x60ac |
| 0x0c45 0x60ae |
| 0x0c45 0x60af |
| 0x0c45 0x60b0 |
| 0x0c45 0x60b2 |
| 0x0c45 0x60b3 |
| 0x0c45 0x60b8 |
| 0x0c45 0x60ba |
| 0x0c45 0x60bb |
| 0x0c45 0x60bc |
| 0x0c45 0x60be |
| |
| The list above does not imply that all those devices work with this driver: up |
| until now only the ones that mount the following image sensors are supported; |
| kernel messages will always tell you whether this is the case: |
| |
| Model Manufacturer |
| ----- ------------ |
| HV7131D Hynix Semiconductor, Inc. |
| MI-0343 Micron Technology, Inc. |
| OV7630 OmniVision Technologies, Inc. |
| PAS106B PixArt Imaging, Inc. |
| PAS202BCA PixArt Imaging, Inc. |
| PAS202BCB PixArt Imaging, Inc. |
| TAS5110C1B Taiwan Advanced Sensor Corporation |
| TAS5130D1B Taiwan Advanced Sensor Corporation |
| |
| All the available control settings of each image sensor are supported through |
| the V4L2 interface. |
| |
| Donations of new models for further testing and support would be much |
| appreciated. Non-available hardware will not be supported by the author of this |
| driver. |
| |
| |
| 10. Notes for V4L2 application developers |
| ========================================= |
| This driver follows the V4L2 API specifications. In particular, it enforces two |
| rules: |
| |
| - exactly one I/O method, either "mmap" or "read", is associated with each |
| file descriptor. Once it is selected, the application must close and reopen the |
| device to switch to the other I/O method; |
| |
| - although it is not mandatory, previously mapped buffer memory should always |
| be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's. |
| The same number of buffers as before will be allocated again to match the size |
| of the new video frames, so you have to map the buffers again before any I/O |
| attempts on them. |
| |
| Consistently with the hardware limits, this driver also supports image |
| downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions. |
| However, the V4L2 API specifications don't correctly define how the scaling |
| factor can be chosen arbitrarily by the "negotiation" of the "source" and |
| "target" rectangles. To work around this flaw, we have added the convention |
| that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the |
| scaling factor is restored to 1. |
| |
| This driver supports two different video formats: the first one is the "8-bit |
| Sequential Bayer" format and can be used to obtain uncompressed video data |
| from the device through the current I/O method, while the second one provides |
| "raw" compressed video data (without frame headers not related to the |
| compressed data). The compression quality may vary from 0 to 1 and can be |
| selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2 |
| ioctl's. For maximum flexibility, both the default active video format and the |
| default compression quality depend on how the image sensor being used is |
| initialized (as described in the documentation of the API for the image sensors |
| supplied by this driver). |
| |
| |
| 11. Video frame formats [1] |
| ======================= |
| The SN9C10x PC Camera Controllers can send images in two possible video |
| formats over the USB: either native "Sequential RGB Bayer" or Huffman |
| compressed. The latter is used to achieve high frame rates. The current video |
| format may be selected or queried from the user application by calling the |
| VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2 API |
| specifications. |
| |
| The name "Sequential Bayer" indicates the organization of the red, green and |
| blue pixels in one video frame. Each pixel is associated with a 8-bit long |
| value and is disposed in memory according to the pattern shown below: |
| |
| B[0] G[1] B[2] G[3] ... B[m-2] G[m-1] |
| G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1] |
| ... |
| ... B[(n-1)(m-2)] G[(n-1)(m-1)] |
| ... G[n(m-2)] R[n(m-1)] |
| |
| The above matrix also represents the sequential or progressive read-out mode of |
| the (n, m) Bayer color filter array used in many CCD/CMOS image sensors. |
| |
| One compressed video frame consists of a bitstream that encodes for every R, G, |
| or B pixel the difference between the value of the pixel itself and some |
| reference pixel value. Pixels are organised in the Bayer pattern and the Bayer |
| sub-pixels are tracked individually and alternatingly. For example, in the |
| first line values for the B and G1 pixels are alternatingly encoded, while in |
| the second line values for the G2 and R pixels are alternatingly encoded. |
| |
| The pixel reference value is calculated as follows: |
| - the 4 top left pixels are encoded in raw uncompressed 8-bit format; |
| - the value in the top two rows is the value of the pixel left of the current |
| pixel; |
| - the value in the left column is the value of the pixel above the current |
| pixel; |
| - for all other pixels, the reference value is the average of the value of the |
| pixel on the left and the value of the pixel above the current pixel; |
| - there is one code in the bitstream that specifies the value of a pixel |
| directly (in 4-bit resolution); |
| - pixel values need to be clamped inside the range [0..255] for proper |
| decoding. |
| |
| The algorithm purely describes the conversion from compressed Bayer code used |
| in the SN9C10x chips to uncompressed Bayer. Additional steps are required to |
| convert this to a color image (i.e. a color interpolation algorithm). |
| |
| The following Huffman codes have been found: |
| 0: +0 (relative to reference pixel value) |
| 100: +4 |
| 101: -4? |
| 1110xxxx: set absolute value to xxxx.0000 |
| 1101: +11 |
| 1111: -11 |
| 11001: +20 |
| 110000: -20 |
| 110001: ??? - these codes are apparently not used |
| |
| [1] The Huffman compression algorithm has been reverse-engineered and |
| documented by Bertrik Sikken. |
| |
| |
| 12. Contact information |
| ======================= |
| The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>. |
| |
| GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is |
| 'FCE635A4'; the public 1024-bit key should be available at any keyserver; |
| the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'. |
| |
| |
| 13. Credits |
| =========== |
| Many thanks to following persons for their contribute (listed in alphabetical |
| order): |
| |
| - Luca Capello for the donation of a webcam; |
| - Philippe Coval for having helped testing the PAS202BCA image sensor; |
| - Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the |
| donation of a webcam; |
| - Jon Hollstrom for the donation of a webcam; |
| - Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB |
| image sensor; |
| - Stefano Mozzi, who donated 45 EU; |
| - Andrew Pearce for the donation of a webcam; |
| - Bertrik Sikken, who reverse-engineered and documented the Huffman compression |
| algorithm used in the SN9C10x controllers and implemented the first decoder; |
| - Mizuno Takafumi for the donation of a webcam; |
| - an "anonymous" donator (who didn't want his name to be revealed) for the |
| donation of a webcam. |