summaryrefslogtreecommitdiffstats
path: root/Documentation/userspace-api/media/v4l/vidioc-g-modulator.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/userspace-api/media/v4l/vidioc-g-modulator.rst')
-rw-r--r--Documentation/userspace-api/media/v4l/vidioc-g-modulator.rst193
1 files changed, 193 insertions, 0 deletions
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.