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diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-modulator.rst b/Documentation/userspace-api/media/v4l/vidioc-g-modulator.rst new file mode 100644 index 000000000..6bdf925f9 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-g-modulator.rst @@ -0,0 +1,193 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_G_MODULATOR: + +******************************************** +ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR +******************************************** + +Name +==== + +VIDIOC_G_MODULATOR - VIDIOC_S_MODULATOR - Get or set modulator attributes + +Synopsis +======== + +.. c:macro:: VIDIOC_G_MODULATOR + +``int ioctl(int fd, VIDIOC_G_MODULATOR, struct v4l2_modulator *argp)`` + +.. c:macro:: VIDIOC_S_MODULATOR + +``int ioctl(int fd, VIDIOC_S_MODULATOR, const struct v4l2_modulator *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_modulator`. + +Description +=========== + +To query the attributes of a modulator applications initialize the +``index`` field and zero out the ``reserved`` array of a struct +:c:type:`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. + +.. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{2.4cm}| + +.. c:type:: v4l2_modulator + +.. flat-table:: struct v4l2_modulator + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 1 1 + + * - __u32 + - ``index`` + - Identifies the modulator, set by the application. + * - __u8 + - ``name``\ [32] + - Name of the modulator, a NUL-terminated ASCII string. + + This information is intended for the user. + * - __u32 + - ``capability`` + - Modulator capability flags. No flags are defined for this field, + the tuner flags in struct :c:type:`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. + * - __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. + * - __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. + * - __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. + * - __u32 + - ``type`` + - :cspan:`2` Type of the modulator, see :c:type:`v4l2_tuner_type`. + * - __u32 + - ``reserved``\ [3] + - Reserved for future extensions. + + Drivers and applications must set the array to zero. + +.. tabularcolumns:: |p{6.0cm}|p{2.0cm}|p{9.3cm}| + +.. cssclass:: longtable + +.. _modulator-txsubchans: + +.. flat-table:: Modulator Audio Transmission Flags + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - ``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``. + * - ``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. + * - ``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. + * - ``V4L2_TUNER_SUB_LANG2`` + - 0x0004 + - Same effect as ``V4L2_TUNER_SUB_SAP``. + * - ``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. + * - ``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 :c:type:`v4l2_modulator` ``index`` is + out of bounds. |