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diff --git a/Documentation/media/uapi/v4l/vidioc-g-modulator.rst b/Documentation/media/uapi/v4l/vidioc-g-modulator.rst new file mode 100644 index 000000000000..05d83610bdc5 --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-g-modulator.rst @@ -0,0 +1,255 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_G_MODULATOR: + +******************************************** +ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR +******************************************** + +Name +==== + +VIDIOC_G_MODULATOR - VIDIOC_S_MODULATOR - Get or set modulator attributes + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, struct v4l2_modulator *argp ) + +.. cpp:function:: int ioctl( int fd, int request, const struct v4l2_modulator *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR + +``argp`` + + +Description +=========== + +To query the attributes of a modulator applications initialize the +``index`` field and zero out the ``reserved`` array of a struct +:ref:`v4l2_modulator <v4l2-modulator>` and call the +:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl with a pointer to this structure. Drivers +fill the rest of the structure or return an ``EINVAL`` error code when the +index is out of bounds. To enumerate all modulators applications shall +begin at index zero, incrementing by one until the driver returns +EINVAL. + +Modulators have two writable properties, an audio modulation set and the +radio frequency. To change the modulated audio subprograms, applications +initialize the ``index`` and ``txsubchans`` fields and the ``reserved`` +array and call the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl. Drivers may choose a +different audio modulation if the request cannot be satisfied. However +this is a write-only ioctl, it does not return the actual audio +modulation selected. + +:ref:`SDR <sdr>` specific modulator types are ``V4L2_TUNER_SDR`` and +``V4L2_TUNER_RF``. For SDR devices ``txsubchans`` field must be +initialized to zero. The term 'modulator' means SDR transmitter in this +context. + +To change the radio frequency the +:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl is available. + + +.. _v4l2-modulator: + +.. flat-table:: struct v4l2_modulator + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 1 1 + + + - .. row 1 + + - __u32 + + - ``index`` + + - Identifies the modulator, set by the application. + + - .. row 2 + + - __u8 + + - ``name``\ [32] + + - Name of the modulator, a NUL-terminated ASCII string. This + information is intended for the user. + + - .. row 3 + + - __u32 + + - ``capability`` + + - Modulator capability flags. No flags are defined for this field, + the tuner flags in struct :ref:`v4l2_tuner <v4l2-tuner>` are + used accordingly. The audio flags indicate the ability to encode + audio subprograms. They will *not* change for example with the + current video standard. + + - .. row 4 + + - __u32 + + - ``rangelow`` + + - The lowest tunable frequency in units of 62.5 KHz, or if the + ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of + 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is + set, in units of 1 Hz. + + - .. row 5 + + - __u32 + + - ``rangehigh`` + + - The highest tunable frequency in units of 62.5 KHz, or if the + ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of + 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is + set, in units of 1 Hz. + + - .. row 6 + + - __u32 + + - ``txsubchans`` + + - With this field applications can determine how audio sub-carriers + shall be modulated. It contains a set of flags as defined in + :ref:`modulator-txsubchans`. Note the tuner ``rxsubchans`` flags + are reused, but the semantics are different. Video output devices + are assumed to have an analog or PCM audio input with 1-3 + channels. The ``txsubchans`` flags select one or more channels for + modulation, together with some audio subprogram indicator, for + example a stereo pilot tone. + + - .. row 7 + + - __u32 + + - ``type`` + + - :cspan:`2` Type of the modulator, see :ref:`v4l2-tuner-type`. + + - .. row 8 + + - __u32 + + - ``reserved``\ [3] + + - Reserved for future extensions. Drivers and applications must set + the array to zero. + + + +.. _modulator-txsubchans: + +.. flat-table:: Modulator Audio Transmission Flags + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + + - .. row 1 + + - ``V4L2_TUNER_SUB_MONO`` + + - 0x0001 + + - Modulate channel 1 as mono audio, when the input has more + channels, a down-mix of channel 1 and 2. This flag does not + combine with ``V4L2_TUNER_SUB_STEREO`` or + ``V4L2_TUNER_SUB_LANG1``. + + - .. row 2 + + - ``V4L2_TUNER_SUB_STEREO`` + + - 0x0002 + + - Modulate channel 1 and 2 as left and right channel of a stereo + audio signal. When the input has only one channel or two channels + and ``V4L2_TUNER_SUB_SAP`` is also set, channel 1 is encoded as + left and right channel. This flag does not combine with + ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_LANG1``. When the + driver does not support stereo audio it shall fall back to mono. + + - .. row 3 + + - ``V4L2_TUNER_SUB_LANG1`` + + - 0x0008 + + - Modulate channel 1 and 2 as primary and secondary language of a + bilingual audio signal. When the input has only one channel it is + used for both languages. It is not possible to encode the primary + or secondary language only. This flag does not combine with + ``V4L2_TUNER_SUB_MONO``, ``V4L2_TUNER_SUB_STEREO`` or + ``V4L2_TUNER_SUB_SAP``. If the hardware does not support the + respective audio matrix, or the current video standard does not + permit bilingual audio the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall + return an ``EINVAL`` error code and the driver shall fall back to mono + or stereo mode. + + - .. row 4 + + - ``V4L2_TUNER_SUB_LANG2`` + + - 0x0004 + + - Same effect as ``V4L2_TUNER_SUB_SAP``. + + - .. row 5 + + - ``V4L2_TUNER_SUB_SAP`` + + - 0x0004 + + - When combined with ``V4L2_TUNER_SUB_MONO`` the first channel is + encoded as mono audio, the last channel as Second Audio Program. + When the input has only one channel it is used for both audio + tracks. When the input has three channels the mono track is a + down-mix of channel 1 and 2. When combined with + ``V4L2_TUNER_SUB_STEREO`` channel 1 and 2 are encoded as left and + right stereo audio, channel 3 as Second Audio Program. When the + input has only two channels, the first is encoded as left and + right channel and the second as SAP. When the input has only one + channel it is used for all audio tracks. It is not possible to + encode a Second Audio Program only. This flag must combine with + ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_STEREO``. If the + hardware does not support the respective audio matrix, or the + current video standard does not permit SAP the + :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall return an ``EINVAL`` error code and + driver shall fall back to mono or stereo mode. + + - .. row 6 + + - ``V4L2_TUNER_SUB_RDS`` + + - 0x0010 + + - Enable the RDS encoder for a radio FM transmitter. + + +Return Value +============ + +On success 0 is returned, on error -1 and the ``errno`` variable is set +appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. + +EINVAL + The struct :ref:`v4l2_modulator <v4l2-modulator>` ``index`` is + out of bounds. |
