Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
Closes the cec device. Resources associated with the file descriptor are
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
The :c:func:`ioctl()` function manipulates cec device parameters. The
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
To open a cec device applications call :c:func:`open()` with the
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
With the :c:func:`poll()` function applications can wait for CEC
Introduction
============
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
HDMI connectors provide a single pin for use by the Consumer Electronics
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
All cec devices must support :ref:`ioctl CEC_ADAP_G_CAPS <CEC_ADAP_G_CAPS>`. To query
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
To query the current CEC logical addresses, applications call
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
To query the current physical address applications call
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
CEC devices can send asynchronous events. These can be retrieved by
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
By default any filehandle can use :ref:`CEC_TRANSMIT`, but in order to prevent
Description
===========
-.. note:: This documents the proposed CEC API. This API is not yet finalized
+.. note::
+
+ This documents the proposed CEC API. This API is not yet finalized
and is currently only available as a staging kernel module.
To receive a CEC message the application has to fill in the
Signal statistics are provided via
:ref:`FE_GET_PROPERTY`.
-.. note:: Most statistics require the demodulator to be fully locked
+.. note::
+
+ Most statistics require the demodulator to be fully locked
(e. g. with FE_HAS_LOCK bit set). See
:ref:`Frontend statistics indicators <frontend-stat-properties>` for
more details.
Part II - Digital TV API
########################
-.. note:: This API is also known as **DVB API**, although it is generic
+.. note::
+
+ This API is also known as **DVB API**, although it is generic
enough to support all digital TV standards.
**Version 5.10**
breaking userspace. So, the decision was to deprecate the legacy
union/struct based approach, in favor of a properties set approach.
-.. note:: On Linux DVB API version 3, setting a frontend were done via
+.. note::
+
+ On Linux DVB API version 3, setting a frontend were done via
:ref:`struct dvb_frontend_parameters <dvb-frontend-parameters>`.
This got replaced on version 5 (also called "S2API", as this API were
added originally_enabled to provide support for DVB-S2), because the
In this section we would like to present some examples for using the DVB
API.
-..note:: This section is out of date, and the code below won't even
+..note::
+
+ This section is out of date, and the code below won't even
compile. Please refer to the
`libdvbv5 <https://linuxtv.org/docs/libdvbv5/index.html>`__ for
updated/recommended examples.
- Capabilities supported by the frontend
-.. note:: The frequencies are specified in Hz for Terrestrial and Cable
+.. note::
+
+ The frequencies are specified in Hz for Terrestrial and Cable
systems. They're specified in kHz for Satellite systems
tuned. The ioctl takes a pointer to an integer where the status will be
written.
-.. note:: The size of status is actually sizeof(enum fe_status), with
+.. note::
+
+ The size of status is actually sizeof(enum fe_status), with
varies according with the architecture. This needs to be fixed in the
future.
Data types and ioctl definitions can be accessed by including
``linux/dvb/frontend.h`` in your application.
-.. note:: Transmission via the internet (DVB-IP) is not yet handled by this
+.. note::
+
+ Transmission via the internet (DVB-IP) is not yet handled by this
API but a future extension is possible.
On Satellite systems, the API support for the Satellite Equipment
also be more precise. On the other hand its disadvantage it usually
reduced range of reception.
-.. note:: Wide band receiver might be implictly enabled if you enable
+.. note::
+
+ Wide band receiver might be implictly enabled if you enable
carrier reports. In that case it will be disabled as soon as you disable
carrier reports. Trying to disable wide band receiver while carrier
reports are active will do nothing.
:ref:`VIDIOC_G_AUDOUT <VIDIOC_G_AUDOUT>` ioctls report the current
audio input and output, respectively.
-.. note:: Note that, unlike :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and
+.. note::
+
+ Note that, unlike :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and
:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` these ioctls return a
structure as :ref:`VIDIOC_ENUMAUDIO` and
:ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDOUT>` do, not just an index.
output device because the application did not pass new data in
time.
- .. note:: This may count the frames received e.g. over USB, without
+ .. note::
+
+ This may count the frames received e.g. over USB, without
taking into account the frames dropped by the remote hardware due
to limited compression throughput or bus bandwidth. These devices
identify by not enumerating any video standards, see
:ref:`standard`.
+
- .. row 10
- __u32
``bytesused`` will be set to the size of the plane (see the
``length`` field of this struct) by the driver.
- .. note:: Note that the actual image data starts at ``data_offset``
+ .. note::
+
+ Note that the actual image data starts at ``data_offset``
which may not be 0.
- .. row 2
field when ``type`` refers to a capture stream, applications when
it refers to an output stream.
- .. note:: That data_offset is included in ``bytesused``. So the
+ .. note::
+
+ That data_offset is included in ``bytesused``. So the
size of the image in the plane is ``bytesused``-``data_offset``
at offset ``data_offset`` from the start of the plane.
Applications can use the following API to select an area in the video
signal, query the default area and the hardware limits.
-.. note:: Despite their name, the :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>`,
+.. note::
+
+ Despite their name, the :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>`,
:ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` and :ref:`VIDIOC_S_CROP
<VIDIOC_G_CROP>` ioctls apply to input as well as output devices.
:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctls. Their size (and position
where applicable) will be fixed in this case.
-.. note:: All capture and output devices must support the
+.. note::
+
+ All capture and output devices must support the
:ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>` ioctl such that applications
can determine if scaling takes place.
work without special preparations. More advanced applications should
ensure the parameters are suitable before starting I/O.
-.. note:: On the next two examples, a video capture device is assumed;
+.. note::
+
+ On the next two examples, a video capture device is assumed;
change ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` for other types of device.
Example: Resetting the cropping parameters
Video compression codecs use the MPEG controls to setup their codec
parameters
-.. note:: The MPEG controls actually support many more codecs than
+.. note::
+
+ The MPEG controls actually support many more codecs than
just MPEG. See :ref:`mpeg-controls`.
Memory-to-memory devices can often be used as a shared resource: you can
The OSD function is accessible through the same character special file
as the :ref:`Video Output <capture>` function.
-.. note:: The default function of such a ``/dev/video`` device is video
+.. note::
+
+ The default function of such a ``/dev/video`` device is video
capturing or output. The OSD function is only available after calling
the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl.
Video overlay devices are accessed through the same character special
files as :ref:`video capture <capture>` devices.
-.. note:: The default function of a ``/dev/video`` device is video
+.. note::
+
+ The default function of a ``/dev/video`` device is video
capturing. The overlay function is only available after calling
the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl.
:ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`,
:ref:`framebuffer-flags`).
- .. note:: This field was added in Linux 2.6.23, extending the
+ .. note::
+
+ This field was added in Linux 2.6.23, extending the
structure. However the :ref:`VIDIOC_[G|S|TRY]_FMT <VIDIOC_G_FMT>`
ioctls, which take a pointer to a :ref:`v4l2_format <v4l2-format>`
parent structure with padding bytes at the end, are not affected.
For more information see the core RDS standard :ref:`iec62106` and the
RBDS standard :ref:`nrsc4`.
-.. note:: Note that the RBDS standard as is used in the USA is almost
+.. note::
+
+ Note that the RBDS standard as is used in the USA is almost
identical to the RDS standard. Any RDS decoder/encoder can also handle
RBDS. Only some of the fields have slightly different meanings. See the
RBDS standard for more information.
Below all controls within the Codec control class are described. First
the generic controls, then controls specific for certain hardware.
-.. note:: These controls are applicable to all codecs and not just MPEG. The
+.. note::
+
+ These controls are applicable to all codecs and not just MPEG. The
defines are prefixed with V4L2_CID_MPEG/V4L2_MPEG as the controls
were originally made for MPEG codecs and later extended to cover all
encoding formats.
``MAP_SHARED`` allows applications to share the mapped memory with
other (e. g. child-) processes.
- .. note:: The Linux ``videobuf`` module which is used by some
+ .. note::
+
+ The Linux ``videobuf`` module which is used by some
drivers supports only ``MAP_SHARED``. ``MAP_PRIVATE`` requests
copy-on-write semantics. V4L2 applications should not set the
``MAP_PRIVATE``, ``MAP_DENYWRITE``, ``MAP_EXECUTABLE`` or ``MAP_ANON``
or struct :ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>`
needs to be filled in.
-.. note:: The default R'G'B' quantization is full range for all
+.. note::
+
+ The default R'G'B' quantization is full range for all
colorspaces except for BT.2020 which uses limited range R'G'B'
quantization.
is ``V4L2_XFER_FUNC_DCI_P3``. The default Y'CbCr encoding is
``V4L2_YCBCR_ENC_709``.
-.. note:: Note that this colorspace does not specify a
+.. note::
+
+ Note that this colorspace does not specify a
Y'CbCr encoding since it is not meant to be encoded to Y'CbCr. So this
default Y'CbCr encoding was picked because it is the HDTV encoding. The
default Y'CbCr quantization is limited range. The chromaticities of the
- 0.316
-.. note:: This colorspace uses Illuminant C instead of D65 as the white
+.. note::
+
+ This colorspace uses Illuminant C instead of D65 as the white
reference. To correctly convert an image in this colorspace to another
that uses D65 you need to apply a chromatic adaptation algorithm such as
the Bradford method.
with full range quantization where Y' is scaled to [0…255] and Cb/Cr are
scaled to [-128…128] and then clipped to [-128…127].
-.. note:: The JPEG standard does not actually store colorspace
+.. note::
+
+ The JPEG standard does not actually store colorspace
information. So if something other than sRGB is used, then the driver
will have to set that information explicitly. Effectively
``V4L2_COLORSPACE_JPEG`` can be considered to be an abbreviation for
has a depth of 16 bits. The least significant byte is stored at lower
memory addresses (little-endian).
-..note:: The actual sampling precision may be lower than 16 bits,
+..note::
+
+ The actual sampling precision may be lower than 16 bits,
for example 10 bits per pixel with values in tange 0 to 1023.
**Byte Order.**
This is a grey-scale image with a depth of 16 bits per pixel. The most
significant byte is stored at lower memory addresses (big-endian).
-.. note:: Tthe actual sampling precision may be lower than 16 bits, for
+.. note::
+
+ The actual sampling precision may be lower than 16 bits, for
example 10 bits per pixel with values in range 0 to 1023.
**Byte Order.**
This is a grey-scale image with a depth of 16 bits per pixel. The least
significant byte is stored at lower memory addresses (little-endian).
-.. note:: The actual sampling precision may be lower than 16 bits, for
+.. note::
+
+ The actual sampling precision may be lower than 16 bits, for
example 10 bits per pixel with values in range 0 to 1023.
**Byte Order.**
*received* standard can be sensed with the
:ref:`VIDIOC_QUERYSTD` ioctl.
-..note:: The parameter of all these ioctls is a pointer to a
+..note::
+
+ The parameter of all these ioctls is a pointer to a
:ref:`v4l2_std_id <v4l2-std-id>` type (a standard set), *not* an
index into the standard enumeration. Drivers must implement all video
standard ioctls when the device has one or more video inputs or outputs.
also contains signal status information applicable when the tuner of the
current video or radio input is queried.
-.. note:: :ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` does not switch the
+.. note::
+
+ :ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` does not switch the
current tuner, when there is more than one at all. The tuner is solely
determined by the current video input. Drivers must support both ioctls
and set the ``V4L2_CAP_TUNER`` flag in the struct :ref:`v4l2_capability
:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctl.
-.. note:: ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` removes all buffers from
+.. note::
+
+ ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` removes all buffers from
both queues and unlocks all buffers as a side effect. Since there is no
notion of doing anything "now" on a multitasking system, if an
application needs to synchronize with another event it should examine
``VIDIOC_DV_TIMINGS_CAP`` ioctl on a video node and the driver will fill
in the structure.
-.. note:: Drivers may return different values after
+.. note::
+
+ Drivers may return different values after
switching the video input or output.
When implemented by the driver DV capabilities of subdevices can be
DV timings, applications shall begin at index zero, incrementing by one
until the driver returns ``EINVAL``.
-.. note:: Drivers may enumerate a different set of DV timings after
+.. note::
+
+ Drivers may enumerate a different set of DV timings after
switching the video input or output.
When implemented by the driver DV timings of subdevices can be queried
formats are enumerable by beginning at index zero and incrementing by
one until ``EINVAL`` is returned.
-.. note:: After switching input or output the list of enumerated image
+.. note::
+
+ After switching input or output the list of enumerated image
formats may be different.
:stub-columns: 0
:widths: 1 1 2
-
- .. row 1
- __u32
Several image formats are already defined by this specification in
:ref:`pixfmt`.
- .. attention:: These codes are not the same as those used
+ .. attention::
+
+ These codes are not the same as those used
in the Windows world.
- .. row 7
does it make sense to increase the index value to receive more frame
intervals.
-.. note:: The order in which the frame intervals are returned has no
+.. note::
+
+ The order in which the frame intervals are returned has no
special meaning. In particular does it not say anything about potential
default frame intervals.
device supports. Only for the ``V4L2_FRMSIZE_TYPE_DISCRETE`` type does
it make sense to increase the index value to receive more frame sizes.
-.. note:: The order in which the frame sizes are returned has no special
+.. note::
+
+ The order in which the frame sizes are returned has no special
meaning. In particular does it not say anything about potential default
format sizes.
- :cspan:`2` The supported modulation systems of this frequency
band. See :ref:`band-modulation`.
- .. note:: Currently only one modulation system per frequency band
+ .. note::
+
+ Currently only one modulation system per frequency band
is supported. More work will need to be done if multiple
modulation systems are possible. Contact the linux-media
mailing list
bounds. To enumerate all audio outputs applications shall begin at index
zero, incrementing by one until the driver returns ``EINVAL``.
-.. note:: Connectors on a TV card to loop back the received audio signal
+.. note::
+
+ Connectors on a TV card to loop back the received audio signal
to a sound card are not audio outputs in this sense.
See :ref:`VIDIOC_G_AUDIOout <VIDIOC_G_AUDOUT>` for a description of struct
write-only ioctl, it does not return the current audio output attributes
as ``VIDIOC_G_AUDOUT`` does.
-.. note:: Connectors on a TV card to loop back the received audio signal
+.. note::
+
+ Connectors on a TV card to loop back the received audio signal
to a sound card are not audio outputs in this sense.
copying any data. This is an easy way to discover how many EDID blocks
there are.
-.. note:: If there are no EDID blocks available at all, then
+.. note::
+
+ If there are no EDID blocks available at all, then
the driver will set ``blocks`` to 0 and it returns 0.
To set the EDID blocks of a receiver the application has to fill in the
to a value large enough to store the payload result and ``ENOSPC`` is
returned.
- .. note:: For string controls, this ``size`` field should
+ .. note::
+
+ For string controls, this ``size`` field should
not be confused with the length of the string. This field refers
to the size of the memory that contains the string. The actual
*length* of the string may well be much smaller.
control and ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default
value of the control.
- .. note:: You can only get the default value of the control,
+ .. note::
+
+ You can only get the default value of the control,
you cannot set or try it.
For backwards compatibility you can also use a control class here
shall be modulated. It contains a set of flags as defined in
:ref:`modulator-txsubchans`.
- .. note:: The tuner ``rxsubchans`` flags are reused, but the
+ .. 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
driver fills in the remaining fields or returns an ``EINVAL`` error code if
the sliced VBI API is unsupported or ``type`` is invalid.
-.. note:: The ``type`` field was added, and the ioctl changed from read-only
+.. note::
+
+ The ``type`` field was added, and the ioctl changed from read-only
to write-read, in Linux 2.6.19.
carrier for a monaural secondary language. Only
``V4L2_TUNER_ANALOG_TV`` tuners can have this capability.
- .. note:: The ``V4L2_TUNER_CAP_LANG2`` and ``V4L2_TUNER_CAP_SAP``
+ .. note::
+
+ The ``V4L2_TUNER_CAP_LANG2`` and ``V4L2_TUNER_CAP_SAP``
flags are synonyms. ``V4L2_TUNER_CAP_SAP`` applies when the tuner
supports the ``V4L2_STD_NTSC_M`` video standard.
- The tuner receives a Second Audio Program.
- .. note:: The ``V4L2_TUNER_SUB_LANG2`` and ``V4L2_TUNER_SUB_SAP``
+ .. note::
+
+ The ``V4L2_TUNER_SUB_LANG2`` and ``V4L2_TUNER_SUB_SAP``
flags are synonyms. The ``V4L2_TUNER_SUB_SAP`` flag applies
when the current video standard is ``V4L2_STD_NTSC_M``.
``VIDIOC_DQBUF`` failed due to an internal error. Can also indicate
temporary problems like signal loss.
- .. note:: The driver might dequeue an (empty) buffer despite returning
+ .. note::
+
+ The driver might dequeue an (empty) buffer despite returning
an error, or even stop capturing. Reusing such buffer may be unsafe
though and its details (e.g. ``index``) may not be returned either.
It is recommended that drivers indicate recoverable errors by setting
:ref:`v4l2_dv_timings <v4l2-dv-timings>`. Once the hardware detects
the timings, it will fill in the timings structure.
-.. note:: Drivers shall *not* switch timings automatically if new
+.. note::
+
+ Drivers shall *not* switch timings automatically if new
timings are detected. Instead, drivers should send the
``V4L2_EVENT_SOURCE_CHANGE`` event (if they support this) and expect
that userspace will take action by calling :ref:`VIDIOC_QUERY_DV_TIMINGS`.
:ref:`v4l2_queryctrl <v4l2-queryctrl>` ``minimum`` to ``maximum``,
inclusive.
-.. note:: It is possible for ``VIDIOC_QUERYMENU`` to return
+.. note::
+
+ It is possible for ``VIDIOC_QUERYMENU`` to return
an ``EINVAL`` error code for some indices between ``minimum`` and
``maximum``. In that case that particular menu item is not supported by
this driver. Also note that the ``minimum`` value is not necessarily 0.
``_BITMASK``, ``_MENU`` or ``_INTEGER_MENU`` control. Not valid
for other types of controls.
- .. note:: Drivers reset controls to their default value only when
+ .. note::
+
+ Drivers reset controls to their default value only when
the driver is first loaded, never afterwards.
- .. row 8
``_BOOLEAN``, ``_BITMASK``, ``_MENU``, ``_INTEGER_MENU``, ``_U8``
or ``_U16`` control. Not valid for other types of controls.
- .. note:: Drivers reset controls to their default value only when
+ .. note::
+
+ Drivers reset controls to their default value only when
the driver is first loaded, never afterwards.
- .. row 8
case the hardware calculates the gain value based on the lighting
conditions which can change over time.
- .. note:: Setting a new value for a volatile control will have no
+ .. note::
+
+ Setting a new value for a volatile control will have no
effect and no ``V4L2_EVENT_CTRL_CH_VALUE`` will be sent, unless
the ``V4L2_CTRL_FLAG_EXECUTE_ON_WRITE`` flag (see below) is
also set. Otherwise the new value will just be ignored.
the set must contain all standards supported by the current video input
or output.
-.. note:: Drivers shall *not* switch the video standard
+.. note::
+
+ Drivers shall *not* switch the video standard
automatically if a new video standard is detected. Instead, drivers
should send the ``V4L2_EVENT_SOURCE_CHANGE`` event (if they support
this) and expect that userspace will take action by calling
but ``VIDIOC_STREAMOFF`` will return queued buffers to their starting
state as mentioned above.
-.. note:: Applications can be preempted for unknown periods right before
+.. note::
+
+ Applications can be preempted for unknown periods right before
or after the ``VIDIOC_STREAMON`` or ``VIDIOC_STREAMOFF`` calls, there is
no notion of starting or stopping "now". Buffer timestamps can be used
to synchronize with other events.
- Type of the event, see :ref:`event-type`.
- .. note:: ``V4L2_EVENT_ALL`` can be used with
+ .. note::
+
+ ``V4L2_EVENT_ALL`` can be used with
:ref:`VIDIOC_UNSUBSCRIBE_EVENT <VIDIOC_SUBSCRIBE_EVENT>` for
unsubscribing all events at once.
-----
.. note::
+
For a more updated list, please check
https://linuxtv.org/wiki/index.php/Hardware_Device_Information
projects / deliverable / linux.git / commitdiff
