Markus Heiser | 5377d91 | 2016-06-30 15:18:56 +0200 | [diff] [blame^] | 1 | .. -*- coding: utf-8; mode: rst -*- |
| 2 | |
| 3 | .. _vidioc-g-modulator: |
| 4 | |
| 5 | ******************************************** |
| 6 | ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR |
| 7 | ******************************************** |
| 8 | |
| 9 | *man VIDIOC_G_MODULATOR(2)* |
| 10 | |
| 11 | VIDIOC_S_MODULATOR |
| 12 | Get or set modulator attributes |
| 13 | |
| 14 | |
| 15 | Synopsis |
| 16 | ======== |
| 17 | |
| 18 | .. c:function:: int ioctl( int fd, int request, struct v4l2_modulator *argp ) |
| 19 | |
| 20 | .. c:function:: int ioctl( int fd, int request, const struct v4l2_modulator *argp ) |
| 21 | |
| 22 | Arguments |
| 23 | ========= |
| 24 | |
| 25 | ``fd`` |
| 26 | File descriptor returned by :ref:`open() <func-open>`. |
| 27 | |
| 28 | ``request`` |
| 29 | VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR |
| 30 | |
| 31 | ``argp`` |
| 32 | |
| 33 | |
| 34 | Description |
| 35 | =========== |
| 36 | |
| 37 | To query the attributes of a modulator applications initialize the |
| 38 | ``index`` field and zero out the ``reserved`` array of a struct |
| 39 | :ref:`v4l2_modulator <v4l2-modulator>` and call the |
| 40 | ``VIDIOC_G_MODULATOR`` ioctl with a pointer to this structure. Drivers |
| 41 | fill the rest of the structure or return an EINVAL error code when the |
| 42 | index is out of bounds. To enumerate all modulators applications shall |
| 43 | begin at index zero, incrementing by one until the driver returns |
| 44 | EINVAL. |
| 45 | |
| 46 | Modulators have two writable properties, an audio modulation set and the |
| 47 | radio frequency. To change the modulated audio subprograms, applications |
| 48 | initialize the ``index`` and ``txsubchans`` fields and the ``reserved`` |
| 49 | array and call the ``VIDIOC_S_MODULATOR`` ioctl. Drivers may choose a |
| 50 | different audio modulation if the request cannot be satisfied. However |
| 51 | this is a write-only ioctl, it does not return the actual audio |
| 52 | modulation selected. |
| 53 | |
| 54 | :ref:`SDR <sdr>` specific modulator types are ``V4L2_TUNER_SDR`` and |
| 55 | ``V4L2_TUNER_RF``. For SDR devices ``txsubchans`` field must be |
| 56 | initialized to zero. The term 'modulator' means SDR transmitter in this |
| 57 | context. |
| 58 | |
| 59 | To change the radio frequency the |
| 60 | :ref:`VIDIOC_S_FREQUENCY <vidioc-g-frequency>` ioctl is available. |
| 61 | |
| 62 | |
| 63 | .. _v4l2-modulator: |
| 64 | |
| 65 | .. flat-table:: struct v4l2_modulator |
| 66 | :header-rows: 0 |
| 67 | :stub-columns: 0 |
| 68 | :widths: 1 1 2 1 1 |
| 69 | |
| 70 | |
| 71 | - .. row 1 |
| 72 | |
| 73 | - __u32 |
| 74 | |
| 75 | - ``index`` |
| 76 | |
| 77 | - Identifies the modulator, set by the application. |
| 78 | |
| 79 | - .. row 2 |
| 80 | |
| 81 | - __u8 |
| 82 | |
| 83 | - ``name``\ [32] |
| 84 | |
| 85 | - Name of the modulator, a NUL-terminated ASCII string. This |
| 86 | information is intended for the user. |
| 87 | |
| 88 | - .. row 3 |
| 89 | |
| 90 | - __u32 |
| 91 | |
| 92 | - ``capability`` |
| 93 | |
| 94 | - Modulator capability flags. No flags are defined for this field, |
| 95 | the tuner flags in struct :ref:`v4l2_tuner <v4l2-tuner>` are |
| 96 | used accordingly. The audio flags indicate the ability to encode |
| 97 | audio subprograms. They will *not* change for example with the |
| 98 | current video standard. |
| 99 | |
| 100 | - .. row 4 |
| 101 | |
| 102 | - __u32 |
| 103 | |
| 104 | - ``rangelow`` |
| 105 | |
| 106 | - The lowest tunable frequency in units of 62.5 KHz, or if the |
| 107 | ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of |
| 108 | 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is |
| 109 | set, in units of 1 Hz. |
| 110 | |
| 111 | - .. row 5 |
| 112 | |
| 113 | - __u32 |
| 114 | |
| 115 | - ``rangehigh`` |
| 116 | |
| 117 | - The highest tunable frequency in units of 62.5 KHz, or if the |
| 118 | ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of |
| 119 | 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is |
| 120 | set, in units of 1 Hz. |
| 121 | |
| 122 | - .. row 6 |
| 123 | |
| 124 | - __u32 |
| 125 | |
| 126 | - ``txsubchans`` |
| 127 | |
| 128 | - With this field applications can determine how audio sub-carriers |
| 129 | shall be modulated. It contains a set of flags as defined in |
| 130 | :ref:`modulator-txsubchans`. Note the tuner ``rxsubchans`` flags |
| 131 | are reused, but the semantics are different. Video output devices |
| 132 | are assumed to have an analog or PCM audio input with 1-3 |
| 133 | channels. The ``txsubchans`` flags select one or more channels for |
| 134 | modulation, together with some audio subprogram indicator, for |
| 135 | example a stereo pilot tone. |
| 136 | |
| 137 | - .. row 7 |
| 138 | |
| 139 | - __u32 |
| 140 | |
| 141 | - ``type`` |
| 142 | |
| 143 | - :cspan:`2` Type of the modulator, see :ref:`v4l2-tuner-type`. |
| 144 | |
| 145 | - .. row 8 |
| 146 | |
| 147 | - __u32 |
| 148 | |
| 149 | - ``reserved``\ [3] |
| 150 | |
| 151 | - Reserved for future extensions. Drivers and applications must set |
| 152 | the array to zero. |
| 153 | |
| 154 | |
| 155 | |
| 156 | .. _modulator-txsubchans: |
| 157 | |
| 158 | .. flat-table:: Modulator Audio Transmission Flags |
| 159 | :header-rows: 0 |
| 160 | :stub-columns: 0 |
| 161 | :widths: 3 1 4 |
| 162 | |
| 163 | |
| 164 | - .. row 1 |
| 165 | |
| 166 | - ``V4L2_TUNER_SUB_MONO`` |
| 167 | |
| 168 | - 0x0001 |
| 169 | |
| 170 | - Modulate channel 1 as mono audio, when the input has more |
| 171 | channels, a down-mix of channel 1 and 2. This flag does not |
| 172 | combine with ``V4L2_TUNER_SUB_STEREO`` or |
| 173 | ``V4L2_TUNER_SUB_LANG1``. |
| 174 | |
| 175 | - .. row 2 |
| 176 | |
| 177 | - ``V4L2_TUNER_SUB_STEREO`` |
| 178 | |
| 179 | - 0x0002 |
| 180 | |
| 181 | - Modulate channel 1 and 2 as left and right channel of a stereo |
| 182 | audio signal. When the input has only one channel or two channels |
| 183 | and ``V4L2_TUNER_SUB_SAP`` is also set, channel 1 is encoded as |
| 184 | left and right channel. This flag does not combine with |
| 185 | ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_LANG1``. When the |
| 186 | driver does not support stereo audio it shall fall back to mono. |
| 187 | |
| 188 | - .. row 3 |
| 189 | |
| 190 | - ``V4L2_TUNER_SUB_LANG1`` |
| 191 | |
| 192 | - 0x0008 |
| 193 | |
| 194 | - Modulate channel 1 and 2 as primary and secondary language of a |
| 195 | bilingual audio signal. When the input has only one channel it is |
| 196 | used for both languages. It is not possible to encode the primary |
| 197 | or secondary language only. This flag does not combine with |
| 198 | ``V4L2_TUNER_SUB_MONO``, ``V4L2_TUNER_SUB_STEREO`` or |
| 199 | ``V4L2_TUNER_SUB_SAP``. If the hardware does not support the |
| 200 | respective audio matrix, or the current video standard does not |
| 201 | permit bilingual audio the ``VIDIOC_S_MODULATOR`` ioctl shall |
| 202 | return an EINVAL error code and the driver shall fall back to mono |
| 203 | or stereo mode. |
| 204 | |
| 205 | - .. row 4 |
| 206 | |
| 207 | - ``V4L2_TUNER_SUB_LANG2`` |
| 208 | |
| 209 | - 0x0004 |
| 210 | |
| 211 | - Same effect as ``V4L2_TUNER_SUB_SAP``. |
| 212 | |
| 213 | - .. row 5 |
| 214 | |
| 215 | - ``V4L2_TUNER_SUB_SAP`` |
| 216 | |
| 217 | - 0x0004 |
| 218 | |
| 219 | - When combined with ``V4L2_TUNER_SUB_MONO`` the first channel is |
| 220 | encoded as mono audio, the last channel as Second Audio Program. |
| 221 | When the input has only one channel it is used for both audio |
| 222 | tracks. When the input has three channels the mono track is a |
| 223 | down-mix of channel 1 and 2. When combined with |
| 224 | ``V4L2_TUNER_SUB_STEREO`` channel 1 and 2 are encoded as left and |
| 225 | right stereo audio, channel 3 as Second Audio Program. When the |
| 226 | input has only two channels, the first is encoded as left and |
| 227 | right channel and the second as SAP. When the input has only one |
| 228 | channel it is used for all audio tracks. It is not possible to |
| 229 | encode a Second Audio Program only. This flag must combine with |
| 230 | ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_STEREO``. If the |
| 231 | hardware does not support the respective audio matrix, or the |
| 232 | current video standard does not permit SAP the |
| 233 | ``VIDIOC_S_MODULATOR`` ioctl shall return an EINVAL error code and |
| 234 | driver shall fall back to mono or stereo mode. |
| 235 | |
| 236 | - .. row 6 |
| 237 | |
| 238 | - ``V4L2_TUNER_SUB_RDS`` |
| 239 | |
| 240 | - 0x0010 |
| 241 | |
| 242 | - Enable the RDS encoder for a radio FM transmitter. |
| 243 | |
| 244 | |
| 245 | |
| 246 | Return Value |
| 247 | ============ |
| 248 | |
| 249 | On success 0 is returned, on error -1 and the ``errno`` variable is set |
| 250 | appropriately. The generic error codes are described at the |
| 251 | :ref:`Generic Error Codes <gen-errors>` chapter. |
| 252 | |
| 253 | EINVAL |
| 254 | The struct :ref:`v4l2_modulator <v4l2-modulator>` ``index`` is |
| 255 | out of bounds. |
| 256 | |
| 257 | |
| 258 | .. ------------------------------------------------------------------------------ |
| 259 | .. This file was automatically converted from DocBook-XML with the dbxml |
| 260 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes |
| 261 | .. from the linux kernel, refer to: |
| 262 | .. |
| 263 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook |
| 264 | .. ------------------------------------------------------------------------------ |