SYNOPSIS
int ioctl(int fd, int request =
-:ref:`FE_DISHNETWORK_SEND_LEGACY_CMD <FE_DISHNETWORK_SEND_LEGACY_CMD>`,
+:ref:`FE_DISHNETWORK_SEND_LEGACY_CMD`,
unsigned long cmd);
PARAMETERS
- int request
- - Equals :ref:`FE_GET_EVENT <FE_GET_EVENT>` for this command.
+ - Equals :ref:`FE_GET_EVENT` for this command.
- .. row 3
SYNOPSIS
int ioctl(int fd, int request =
-:ref:`FE_GET_FRONTEND <FE_GET_FRONTEND>`, struct
+:ref:`FE_GET_FRONTEND`, struct
dvb_frontend_parameters *p);
PARAMETERS
- int request
- - Equals :ref:`FE_SET_FRONTEND <FE_SET_FRONTEND>` for this
+ - Equals :ref:`FE_SET_FRONTEND` for this
command.
- .. row 3
SYNOPSIS
-int ioctl(int fd, int request = :ref:`FE_READ_BER <FE_READ_BER>`,
+int ioctl(int fd, int request = :ref:`FE_READ_BER`,
uint32_t *ber);
PARAMETERS
- int request
- - Equals :ref:`FE_READ_BER <FE_READ_BER>` for this command.
+ - Equals :ref:`FE_READ_BER` for this command.
- .. row 3
SYNOPSIS
int ioctl( int fd, int request =
-:ref:`FE_READ_SIGNAL_STRENGTH <FE_READ_SIGNAL_STRENGTH>`,
+:ref:`FE_READ_SIGNAL_STRENGTH`,
uint16_t *strength);
PARAMETERS
- int request
- Equals
- :ref:`FE_READ_SIGNAL_STRENGTH <FE_READ_SIGNAL_STRENGTH>`
+ :ref:`FE_READ_SIGNAL_STRENGTH`
for this command.
- .. row 3
SYNOPSIS
-int ioctl(int fd, int request = :ref:`FE_READ_SNR <FE_READ_SNR>`,
+int ioctl(int fd, int request = :ref:`FE_READ_SNR`,
uint16_t *snr);
PARAMETERS
- int request
- - Equals :ref:`FE_READ_SNR <FE_READ_SNR>` for this command.
+ - Equals :ref:`FE_READ_SNR` for this command.
- .. row 3
SYNOPSIS
int ioctl( int fd, int request =
-:ref:`FE_READ_UNCORRECTED_BLOCKS <FE_READ_UNCORRECTED_BLOCKS>`,
+:ref:`FE_READ_UNCORRECTED_BLOCKS`,
uint32_t *ublocks);
PARAMETERS
- int request
- Equals
- :ref:`FE_READ_UNCORRECTED_BLOCKS <FE_READ_UNCORRECTED_BLOCKS>`
+ :ref:`FE_READ_UNCORRECTED_BLOCKS`
for this command.
- .. row 3
The result of this call will be successful if the parameters were valid
and the tuning could be initiated. The result of the tuning operation in
itself, however, will arrive asynchronously as an event (see
-documentation for :ref:`FE_GET_EVENT <FE_GET_EVENT>` and
-FrontendEvent.) If a new :ref:`FE_SET_FRONTEND <FE_SET_FRONTEND>`
+documentation for :ref:`FE_GET_EVENT` and
+FrontendEvent.) If a new :ref:`FE_SET_FRONTEND`
operation is initiated before the previous one was completed, the
previous operation will be aborted in favor of the new one. This command
requires read/write access to the device.
SYNOPSIS
int ioctl(int fd, int request =
-:ref:`FE_SET_FRONTEND <FE_SET_FRONTEND>`, struct
+:ref:`FE_SET_FRONTEND`, struct
dvb_frontend_parameters *p);
PARAMETERS
- int request
- - Equals :ref:`FE_SET_FRONTEND <FE_SET_FRONTEND>` for this
+ - Equals :ref:`FE_SET_FRONTEND` for this
command.
- .. row 3
DESCRIPTION
This ioctl is for DVB devices only. To control a V4L2 decoder use the
-V4L2 :ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` with the
+V4L2 :ref:`VIDIOC_DECODER_CMD` with the
``V4L2_DEC_CMD_START_MUTE_AUDIO`` flag instead.
This ioctl call asks the audio device to mute the stream that is
signal.
The information about the frontend tuner locking status can be queried
-using :ref:`FE_READ_STATUS <FE_READ_STATUS>`.
+using :ref:`FE_READ_STATUS`.
Signal statistics are provided via
-:ref:`FE_GET_PROPERTY <FE_GET_PROPERTY>`. Please note that several
+:ref:`FE_GET_PROPERTY`. Please note that several
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
It can be used to calculate the PER indicator, by dividing
:ref:`DTV_STAT_ERROR_BLOCK_COUNT <DTV-STAT-ERROR-BLOCK-COUNT>` by
-:ref:`DTV-STAT-TOTAL-BLOCK-COUNT <DTV-STAT-TOTAL-BLOCK-COUNT>`.
+:ref:`DTV-STAT-TOTAL-BLOCK-COUNT`.
Possible scales for this metric are:
This system call opens a named frontend device
(``/dev/dvb/adapter?/frontend?``) for subsequent use. Usually the first
thing to do after a successful open is to find out the frontend type
-with :ref:`FE_GET_INFO <FE_GET_INFO>`.
+with :ref:`FE_GET_INFO`.
The device can be opened in read-only mode, which only allows monitoring
of device status and statistics, or read/write mode, which allows any
Usually, the first thing to do when the frontend is opened is to check
the frontend capabilities. This is done using
-:ref:`FE_GET_INFO <FE_GET_INFO>`. This ioctl will enumerate the
+:ref:`FE_GET_INFO`. This ioctl will enumerate the
DVB API version and other characteristics about the frontend, and can be
opened either in read only or read/write mode.
DESCRIPTION
This ioctl is for DVB devices only. To control a V4L2 decoder use the
-V4L2 :ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` instead.
+V4L2 :ref:`VIDIOC_DECODER_CMD` instead.
This ioctl call asks the Video Device to stop playing the current
stream. Depending on the input parameter, the screen can be blanked out
DESCRIPTION
This ioctl is for DVB devices only. To control a V4L2 decoder use the
-V4L2 :ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` instead.
+V4L2 :ref:`VIDIOC_DECODER_CMD` instead.
This ioctl call asks the Video Device to start playing a video stream
from the selected source.
DESCRIPTION
This ioctl is for DVB devices only. To control a V4L2 decoder use the
-V4L2 :ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` instead.
+V4L2 :ref:`VIDIOC_DECODER_CMD` instead.
This ioctl call suspends the live video stream being played. Decoding
and playing are frozen. It is then possible to restart the decoding and
DESCRIPTION
This ioctl is for DVB devices only. To control a V4L2 decoder use the
-V4L2 :ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` instead.
+V4L2 :ref:`VIDIOC_DECODER_CMD` instead.
This ioctl call restarts decoding and playing processes of the video
stream which was played before a call to VIDEO_FREEZE was made.
DESCRIPTION
This ioctl is for DVB devices only. To get events from a V4L2 decoder
-use the V4L2 :ref:`VIDIOC_DQEVENT <VIDIOC_DQEVENT>` ioctl instead.
+use the V4L2 :ref:`VIDIOC_DQEVENT` ioctl instead.
This ioctl call returns an event of type video_event if available. If
an event is not available, the behavior depends on whether the device is
This ioctl is obsolete. Do not use in new drivers. For V4L2 decoders
this ioctl has been replaced by the
-:ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` ioctl.
+:ref:`VIDIOC_DECODER_CMD` ioctl.
This ioctl commands the decoder. The ``video_command`` struct is a
subset of the ``v4l2_decoder_cmd`` struct, so refer to the
-:ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>` documentation for
+:ref:`VIDIOC_DECODER_CMD` documentation for
more information.
SYNOPSIS
time.
Since these features cannot be implemented entirely in user space V4L2
-defines the :ref:`VIDIOC_G_PRIORITY <VIDIOC_G_PRIORITY>` and
+defines the :ref:`VIDIOC_G_PRIORITY` and
:ref:`VIDIOC_S_PRIORITY <VIDIOC_G_PRIORITY>` ioctls to request and
query the access priority associate with a file descriptor. Opening a
device assigns a medium priority, compatible with earlier versions of
V4L2 and drivers not supporting these ioctls. Applications requiring a
different priority will usually call :ref:`VIDIOC_S_PRIORITY
<VIDIOC_G_PRIORITY>` after verifying the device with the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl.
+:ref:`VIDIOC_QUERYCAP` ioctl.
Ioctls changing driver properties, such as
:ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>`, return an EBUSY error code
To learn about the number and attributes of the available inputs and
outputs applications can enumerate them with the
-:ref:`VIDIOC_ENUMAUDIO <VIDIOC_ENUMAUDIO>` and
+:ref:`VIDIOC_ENUMAUDIO` and
:ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDIOout>` ioctl, respectively.
The struct :ref:`v4l2_audio <v4l2-audio>` returned by the
-:ref:`VIDIOC_ENUMAUDIO <VIDIOC_ENUMAUDIO>` ioctl also contains signal
+:ref:`VIDIOC_ENUMAUDIO` ioctl also contains signal
:status information applicable when the current audio input is queried.
-The :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` and
+The :ref:`VIDIOC_G_AUDIO` and
:ref:`VIDIOC_G_AUDOUT <VIDIOC_G_AUDIOout>` ioctls report the current
audio input and output, respectively. 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 <VIDIOC_ENUMAUDIO>` and
+:ref:`VIDIOC_G_INPUT` and
+:ref:`VIDIOC_G_OUTPUT` these ioctls return a
+structure as :ref:`VIDIOC_ENUMAUDIO` and
:ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDIOout>` do, not just an index.
To select an audio input and change its properties applications call the
device has multiple selectable audio outputs. When the device has any
audio inputs or outputs the driver must set the ``V4L2_CAP_AUDIO`` flag
in the struct :ref:`v4l2_capability <v4l2-capability>` returned by
-the :ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl.
+the :ref:`VIDIOC_QUERYCAP` ioctl.
.. code-block:: c
Only pointers to buffers (planes) are exchanged, the data itself is not
copied. These pointers, together with meta-information like timestamps
or field parity, are stored in a struct :c:type:`struct v4l2_buffer`,
-argument to the :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`,
-:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` and
+argument to the :ref:`VIDIOC_QUERYBUF`,
+:ref:`VIDIOC_QBUF` and
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. In the multi-planar API,
some plane-specific members of struct :c:type:`struct v4l2_buffer`,
such as pointers and sizes for each plane, are stored in struct
- Number of the buffer, set by the application except when calling
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, then it is set by the
driver. This field can range from zero to the number of buffers
- allocated with the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl
+ allocated with the :ref:`VIDIOC_REQBUFS` ioctl
(struct :ref:`v4l2_requestbuffers <v4l2-requestbuffers>`
``count``), plus any buffers allocated with
- :ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>` minus one.
+ :ref:`VIDIOC_CREATE_BUFS` minus one.
- .. row 2
-
- Size of the buffer (not the payload) in bytes for the
single-planar API. This is set by the driver based on the calls to
- :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` and/or
- :ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>`. For the
+ :ref:`VIDIOC_REQBUFS` and/or
+ :ref:`VIDIOC_CREATE_BUFS`. For the
multi-planar API the application sets this to the number of
elements in the ``planes`` array. The driver will fill in the
actual number of valid elements in that array.
-
- Size in bytes of the plane (not its payload). This is set by the
driver based on the calls to
- :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` and/or
- :ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>`.
+ :ref:`VIDIOC_REQBUFS` and/or
+ :ref:`VIDIOC_CREATE_BUFS`.
- .. row 3
- The buffer resides in device memory and has been mapped into the
application's address space, see :ref:`mmap` for details.
Drivers set or clear this flag when the
- :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`,
- :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` or
+ :ref:`VIDIOC_QUERYBUF`,
+ :ref:`VIDIOC_QBUF` or
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl is called. Set by the
driver.
- The buffer has been prepared for I/O and can be queued by the
application. Drivers set or clear this flag when the
- :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`,
+ :ref:`VIDIOC_QUERYBUF`,
:ref:`VIDIOC_PREPARE_BUF <VIDIOC_QBUF>`,
- :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` or
+ :ref:`VIDIOC_QBUF` or
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl is called.
- .. row 10
- Last buffer produced by the hardware. mem2mem codec drivers set
this flag on the capture queue for the last buffer when the
- :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` or
+ :ref:`VIDIOC_QUERYBUF` or
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl is called. Due to
hardware limitations, the last buffer may be empty. In this case
the driver will set the ``bytesused`` field to 0, regardless of
V4L2 specifies an event mechanism to notify applications when controls
change value (see
-:ref:`VIDIOC_SUBSCRIBE_EVENT <VIDIOC_SUBSCRIBE_EVENT>`, event
+:ref:`VIDIOC_SUBSCRIBE_EVENT`, event
``V4L2_EVENT_CTRL``), panel applications might want to make use of that
in order to always reflect the correct control value.
and version, see :ref:`querycap`.
Applications can enumerate the available controls with the
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` and
+:ref:`VIDIOC_QUERYCTRL` and
:ref:`VIDIOC_QUERYMENU <VIDIOC_QUERYCTRL>` ioctls, get and set a
-control value with the :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
+control value with the :ref:`VIDIOC_G_CTRL` and
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls. Drivers must implement
``VIDIOC_QUERYCTRL``, ``VIDIOC_G_CTRL`` and ``VIDIOC_S_CTRL`` when the
device has one or more controls, ``VIDIOC_QUERYMENU`` when it has one or
the real IDs.
Many applications today still use the ``V4L2_CID_PRIVATE_BASE`` IDs
- instead of using :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` with
+ instead of using :ref:`VIDIOC_QUERYCTRL` with
the ``V4L2_CTRL_FLAG_NEXT_CTRL`` flag to enumerate all IDs, so
support for ``V4L2_CID_PRIVATE_BASE`` is still around.
Applications can use the following API to select an area in the video
signal, query the default area and the hardware limits. *Despite their
-name, the :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>`,
-:ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` and
+name, the :ref:`VIDIOC_CROPCAP`,
+:ref:`VIDIOC_G_CROP` and
:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctls apply to input as well
as output devices.*
device the source is the video signal, and the cropping ioctls determine
the area actually sampled. The target are images read by the application
or overlaid onto the graphics screen. Their size (and position for an
-overlay) is negotiated with the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`
+overlay) is negotiated with the :ref:`VIDIOC_G_FMT`
and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls.
On a video output device the source are the images passed in by the
``V4L2_CAP_VIDEO_CAPTURE`` or ``V4L2_CAP_VIDEO_CAPTURE_MPLANE`` flag in
the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. As secondary device
+:ref:`VIDIOC_QUERYCAP` ioctl. As secondary device
functions they may also support the :ref:`video overlay <overlay>`
(``V4L2_CAP_VIDEO_OVERLAY``) and the :ref:`raw VBI capture <raw-vbi>`
(``V4L2_CAP_VBI_CAPTURE``) interface. At least one of the read/write or
======================
Video capture devices shall support :ref:`audio input <audio>`,
-:ref:`tuner <tuner>`, :ref:`controls <control>`,
+:ref:`tuner`, :ref:`controls <control>`,
:ref:`cropping and scaling <crop>` and
:ref:`streaming parameter <streaming-par>` ioctls as needed. The
:ref:`video input <video>` and :ref:`video standard <standard>`
a struct :ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or
``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and call the
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl with a pointer to this
+:ref:`VIDIOC_G_FMT` ioctl with a pointer to this
structure. Drivers fill the struct
:ref:`v4l2_pix_format <v4l2-pix-format>` ``pix`` or the struct
:ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` ``pix_mp``
supports both output (sending frames from memory to the codec hardware)
and capture (receiving the processed frames from the codec hardware into
memory) stream I/O. An application will have to setup the stream I/O for
-both sides and finally call :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`
+both sides and finally call :ref:`VIDIOC_STREAMON`
for both capture and output to start the codec.
Video compression codecs use the MPEG controls to setup their codec
To receive events, the events the user is interested in first must be
subscribed using the
-:ref:`VIDIOC_SUBSCRIBE_EVENT <VIDIOC_SUBSCRIBE_EVENT>` ioctl. Once
+:ref:`VIDIOC_SUBSCRIBE_EVENT` ioctl. Once
an event is subscribed, the events of subscribed types are dequeueable
-using the :ref:`VIDIOC_DQEVENT <VIDIOC_DQEVENT>` ioctl. Events may be
+using the :ref:`VIDIOC_DQEVENT` ioctl. Events may be
unsubscribed using VIDIOC_UNSUBSCRIBE_EVENT ioctl. The special event
type V4L2_EVENT_ALL may be used to unsubscribe all the events the
driver supports.
Devices supporting the *Video Output Overlay* interface set the
``V4L2_CAP_VIDEO_OUTPUT_OVERLAY`` flag in the ``capabilities`` field of
struct :ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl.
+:ref:`VIDIOC_QUERYCAP` ioctl.
Framebuffer
implemented on the TV card and not the graphics card. On Linux it is
accessible as a framebuffer device (``/dev/fbN``). Given a V4L2 device,
applications can find the corresponding framebuffer device by calling
-the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` ioctl. It returns, amongst
+the :ref:`VIDIOC_G_FBUF` ioctl. It returns, amongst
other information, the physical address of the framebuffer in the
``base`` field of struct :ref:`v4l2_framebuffer <v4l2-framebuffer>`.
The framebuffer device ioctl ``FBIOGET_FSCREENINFO`` returns the same
parameters applications set the ``type`` field of a struct
:ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY`` and call the
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl. The driver fills the
+:ref:`VIDIOC_G_FMT` ioctl. The driver fills the
:c:type:`struct v4l2_window` substructure named ``win``. It is not
possible to retrieve a previously programmed clipping list or bitmap.
``V4L2_CAP_VIDEO_OUTPUT`` or ``V4L2_CAP_VIDEO_OUTPUT_MPLANE`` flag in
the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. As secondary device
+:ref:`VIDIOC_QUERYCAP` ioctl. As secondary device
functions they may also support the :ref:`raw VBI output <raw-vbi>`
(``V4L2_CAP_VBI_OUTPUT``) interface. At least one of the read/write or
streaming I/O methods must be supported. Modulators and audio outputs
To query the current image format applications set the ``type`` field of
a struct :ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_VIDEO_OUTPUT`` or ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``
-and call the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl with a pointer
+and call the :ref:`VIDIOC_G_FMT` ioctl with a pointer
to this structure. Drivers fill the struct
:ref:`v4l2_pix_format <v4l2-pix-format>` ``pix`` or the struct
:ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` ``pix_mp``
Devices supporting the video overlay interface set the
``V4L2_CAP_VIDEO_OVERLAY`` flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. The overlay I/O
+:ref:`VIDIOC_QUERYCAP` ioctl. The overlay I/O
method specified below must be supported. Tuners and audio inputs are
optional.
======================
Video overlay devices shall support :ref:`audio input <audio>`,
-:ref:`tuner <tuner>`, :ref:`controls <control>`,
+:ref:`tuner`, :ref:`controls <control>`,
:ref:`cropping and scaling <crop>` and
:ref:`streaming parameter <streaming-par>` ioctls as needed. The
:ref:`video input <video>` and :ref:`video standard <standard>`
Before overlay can commence applications must program the driver with
frame buffer parameters, namely the address and size of the frame buffer
and the image format, for example RGB 5:6:5. The
-:ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` and
+:ref:`VIDIOC_G_FBUF` and
:ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` ioctls are available to get and
set these parameters, respectively. The ``VIDIOC_S_FBUF`` ioctl is
privileged because it allows to set up DMA into physical memory,
To get the current parameters applications set the ``type`` field of a
struct :ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_VIDEO_OVERLAY`` and call the
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl. The driver fills the
+:ref:`VIDIOC_G_FMT` ioctl. The driver fills the
:c:type:`struct v4l2_window` substructure named ``win``. It is not
possible to retrieve a previously programmed clipping list or bitmap.
``struct v4l2_clip * clips``
When chroma-keying has *not* been negotiated and
- :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` indicated this capability,
+ :ref:`VIDIOC_G_FBUF` indicated this capability,
applications can set this field to point to an array of clipping
rectangles.
``void * bitmap``
When chroma-keying has *not* been negotiated and
- :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` indicated this capability,
+ :ref:`VIDIOC_G_FBUF` indicated this capability,
applications can set this field to point to a clipping bit mask.
It must be of the same size as the window, ``w.width`` and ``w.height``.
================
To start or stop the frame buffer overlay applications call the
-:ref:`VIDIOC_OVERLAY <VIDIOC_OVERLAY>` ioctl.
+:ref:`VIDIOC_OVERLAY` ioctl.
.. [1]
A common application of two file descriptors is the XFree86
``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` flag in the
``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. Other combinations of
+:ref:`VIDIOC_QUERYCAP` ioctl. Other combinations of
capability flags are reserved for future extensions.
frequency and to determine if a monaural or FM stereo program is
received/emitted. Drivers switch automatically between AM and FM
depending on the selected frequency. The
-:ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` or
-:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl reports the
+:ref:`VIDIOC_G_TUNER` or
+:ref:`VIDIOC_G_MODULATOR` ioctl reports the
supported frequency range.
``V4L2_CAP_VBI_CAPTURE`` or ``V4L2_CAP_VBI_OUTPUT`` flags, respectively,
in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. At least one of the
+:ref:`VIDIOC_QUERYCAP` ioctl. At least one of the
read/write, streaming or asynchronous I/O methods must be supported. VBI
devices may or may not have a tuner or modulator.
To query the current raw VBI capture parameters applications set the
``type`` field of a struct :ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_VBI_CAPTURE`` or ``V4L2_BUF_TYPE_VBI_OUTPUT``, and call
-the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl with a pointer to this
+the :ref:`VIDIOC_G_FMT` ioctl with a pointer to this
structure. Drivers fill the struct
:ref:`v4l2_vbi_format <v4l2-vbi-format>` ``vbi`` member of the
``fmt`` union.
overlap, or when the driver supports multiple opens and another process
already requested VBI capturing or output. Anyway, applications must
expect other resource allocation points which may return EBUSY, at the
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` ioctl and the first read(),
+:ref:`VIDIOC_STREAMON` ioctl and the first read(),
write() and select() call.
VBI devices must implement both the ``VIDIOC_G_FMT`` and
The latter bears the possibility of synchronizing video and VBI data by
using buffer timestamps.
-Remember the :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` ioctl and the
+Remember the :ref:`VIDIOC_STREAMON` ioctl and the
first read(), write() and select() call can be resource allocation
points returning an EBUSY error code if the required hardware resources
are temporarily unavailable, for example the device is already in use by
Devices supporting the RDS capturing API set the
``V4L2_CAP_RDS_CAPTURE`` flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. Any tuner that
+:ref:`VIDIOC_QUERYCAP` ioctl. Any tuner that
supports RDS will set the ``V4L2_TUNER_CAP_RDS`` flag in the
``capability`` field of struct :ref:`v4l2_tuner <v4l2-tuner>`. If the
driver only passes RDS blocks without interpreting the data the
Devices supporting the RDS output API set the ``V4L2_CAP_RDS_OUTPUT``
flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. Any modulator that
+:ref:`VIDIOC_QUERYCAP` ioctl. Any modulator that
supports RDS will set the ``V4L2_TUNER_CAP_RDS`` flag in the
``capability`` field of struct
:ref:`v4l2_modulator <v4l2-modulator>`. In order to enable the RDS
``V4L2_CAP_SDR_CAPTURE`` and ``V4L2_CAP_TUNER`` flag in the
``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. That flag means the
+:ref:`VIDIOC_QUERYCAP` ioctl. That flag means the
device has an Analog to Digital Converter (ADC), which is a mandatory
element for the SDR receiver.
``V4L2_CAP_SDR_OUTPUT`` and ``V4L2_CAP_MODULATOR`` flag in the
``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. That flag means the
+:ref:`VIDIOC_QUERYCAP` ioctl. That flag means the
device has an Digital to Analog Converter (DAC), which is a mandatory
element for the SDR transmitter.
======================
SDR devices can support :ref:`controls <control>`, and must support
-the :ref:`tuner <tuner>` ioctls. Tuner ioctls are used for setting the
+the :ref:`tuner` ioctls. Tuner ioctls are used for setting the
ADC/DAC sampling rate (sampling frequency) and the possible radio
frequency (RF).
follow the SDR tuner index. Normally the SDR tuner is #0 and the RF
tuner is #1.
-The :ref:`VIDIOC_S_HW_FREQ_SEEK <VIDIOC_S_HW_FREQ_SEEK>` ioctl is
+The :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl is
not supported.
Data Format Negotiation
=======================
-The SDR device uses the :ref:`format <format>` ioctls to select the
+The SDR device uses the :ref:`format` ioctls to select the
capture and output format. Both the sampling resolution and the data
streaming format are bound to that selectable format. In addition to the
-basic :ref:`format <format>` ioctls, the
-:ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` ioctl must be supported as
+basic :ref:`format` ioctls, the
+:ref:`VIDIOC_ENUM_FMT` ioctl must be supported as
well.
-To use the :ref:`format <format>` ioctls applications set the ``type``
+To use the :ref:`format` ioctls applications set the ``type``
field of a struct :ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_SDR_CAPTURE`` or ``V4L2_BUF_TYPE_SDR_OUTPUT`` and use
the struct :ref:`v4l2_sdr_format <v4l2-sdr-format>` ``sdr`` member
``V4L2_CAP_SLICED_VBI_CAPTURE`` or ``V4L2_CAP_SLICED_VBI_OUTPUT`` flag
respectively, in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. At least one of the
+:ref:`VIDIOC_QUERYCAP` ioctl. At least one of the
read/write, streaming or asynchronous :ref:`I/O methods <io>` must be
supported. Sliced VBI devices may have a tuner or modulator.
Sliced VBI devices shall support :ref:`video input or output <video>`
and :ref:`tuner or modulator <tuner>` ioctls if they have these
-capabilities, and they may support :ref:`control <control>` ioctls.
+capabilities, and they may support :ref:`control` ioctls.
The :ref:`video standard <standard>` ioctls provide information vital
to program a sliced VBI device, therefore must be supported.
To find out which data services are supported by the hardware
applications can call the
-:ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl.
+:ref:`VIDIOC_G_SLICED_VBI_CAP` ioctl.
All drivers implementing the sliced VBI interface must support this
ioctl. The results may differ from those of the
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl when the number of VBI
``type`` field of struct :ref:`v4l2_format <v4l2-format>` to
``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` or
``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``, and the
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl fills the ``fmt.sliced``
+:ref:`VIDIOC_G_FMT` ioctl fills the ``fmt.sliced``
member, a struct
:ref:`v4l2_sliced_vbi_format <v4l2-sliced-vbi-format>`.
at this point, it may return an EBUSY error code if the required
resources are temporarily unavailable. Other resource allocation points
which may return EBUSY can be the
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` ioctl and the first
+:ref:`VIDIOC_STREAMON` ioctl and the first
:ref:`read() <func-read>`, :ref:`write() <func-write>` and
:ref:`select() <func-select>` call.
- :cspan:`2` Maximum number of bytes passed by one
:ref:`read() <func-read>` or :ref:`write() <func-write>` call,
and the buffer size in bytes for the
- :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` and
+ :ref:`VIDIOC_QBUF` and
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. Drivers set this field
to the size of struct
:ref:`v4l2_sliced_vbi_data <v4l2-sliced-vbi-data>` times the
a side effect). The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl may
return an EBUSY error code when applications attempt to change the
format while i/o is in progress (between a
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
+:ref:`VIDIOC_STREAMON` and
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` call, and after the first
:ref:`read() <func-read>` or :ref:`write() <func-write>` call).
Packets are always passed in ascending line number order, without
duplicate line numbers. The :ref:`write() <func-write>` function and
-the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl must return an EINVAL
+the :ref:`VIDIOC_QBUF` ioctl must return an EINVAL
error code when applications violate this rule. They must also return an
EINVAL error code when applications pass an incorrect field or line
number, or a combination of ``field``, ``line`` and ``id`` which has not
-been negotiated with the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` or
+been negotiated with the :ref:`VIDIOC_G_FMT` or
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. When the line numbers are
unknown the driver must pass the packets in transmitted order. The
driver can insert empty packets with ``id`` set to zero anywhere in the
Drivers that implement the :ref:`media API <media-controller-intro>`
can expose pad-level image format configuration to applications. When
they do, applications can use the
-:ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` and
+:ref:`VIDIOC_SUBDEV_G_FMT` and
:ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` ioctls. to
negotiate formats on a per-pad basis.
Applications are responsible for configuring coherent parameters on the
whole pipeline and making sure that connected pads have compatible
formats. The pipeline is checked for formats mismatch at
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` time, and an EPIPE error
+:ref:`VIDIOC_STREAMON` time, and an EPIPE error
code is then returned if the configuration is invalid.
Pad-level image format configuration support can be tested by calling
-the :ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` ioctl on pad
+the :ref:`VIDIOC_SUBDEV_G_FMT` ioctl on pad
0. If the driver returns an EINVAL error code pad-level format
configuration is not supported by the sub-device.
Central to the format negotiation mechanism are the get/set format
operations. When called with the ``which`` argument set to
``V4L2_SUBDEV_FORMAT_TRY``, the
-:ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` and
+:ref:`VIDIOC_SUBDEV_G_FMT` and
:ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` ioctls operate on
a set of formats parameters that are not connected to the hardware
configuration. Modifying those 'try' formats leaves the device state
While not kept as part of the device state, try formats are stored in
the sub-device file handles. A
-:ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` call will return
+:ref:`VIDIOC_SUBDEV_G_FMT` call will return
the last try format set *on the same sub-device file handle*. Several
applications querying the same sub-device at the same time will thus not
interact with each other.
Teletext API in kernel 2.6.37.
Modern devices all use the :ref:`raw <raw-vbi>` or
-:ref:`sliced <sliced>` VBI API.
+:ref:`sliced` VBI API.
.. ------------------------------------------------------------------------------
=====================
The V4L ``VIDIOCGCAP`` ioctl is equivalent to V4L2's
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>`.
+:ref:`VIDIOC_QUERYCAP`.
The ``name`` field in struct :c:type:`struct video_capability` became
``card`` in struct :ref:`v4l2_capability <v4l2-capability>`, ``type``
- ``-``
- Applications can enumerate the supported image formats with the
- :ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` ioctl to determine if
+ :ref:`VIDIOC_ENUM_FMT` ioctl to determine if
the device supports grey scale capturing only. For more
information on image formats see :ref:`pixfmt`.
- ``-``
- - Applications can call the :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>`
+ - Applications can call the :ref:`VIDIOC_G_CROP`
ioctl to determine if the device supports capturing a subsection
of the full picture ("cropping" in V4L2). If not, the ioctl
returns the EINVAL error code. For more information on cropping
- ``-``
- Applications can enumerate the supported image formats with the
- :ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` ioctl to determine if
+ :ref:`VIDIOC_ENUM_FMT` ioctl to determine if
the device supports MPEG streams.
- .. row 13
The ``audios`` field was replaced by ``capabilities`` flag
``V4L2_CAP_AUDIO``, indicating *if* the device has any audio inputs or
outputs. To determine their number applications can enumerate audio
-inputs with the :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl. The
+inputs with the :ref:`VIDIOC_G_AUDIO` ioctl. The
audio ioctls are described in :ref:`audio`.
The ``maxwidth``, ``maxheight``, ``minwidth`` and ``minheight`` fields
V4L provides the ``VIDIOCGCHAN`` and ``VIDIOCSCHAN`` ioctl using struct
:c:type:`struct video_channel` to enumerate the video inputs of a V4L
device. The equivalent V4L2 ioctls are
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>`,
-:ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and
+:ref:`VIDIOC_ENUMINPUT`,
+:ref:`VIDIOC_G_INPUT` and
:ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>` using struct
:ref:`v4l2_input <v4l2-input>` as discussed in :ref:`video`.
The V4L ``VIDIOCGTUNER`` and ``VIDIOCSTUNER`` ioctl and struct
:c:type:`struct video_tuner` can be used to enumerate the tuners of a
V4L TV or radio device. The equivalent V4L2 ioctls are
-:ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` and
+:ref:`VIDIOC_G_TUNER` and
:ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` using struct
:ref:`v4l2_tuner <v4l2-tuner>`. Tuners are covered in :ref:`tuner`.
The ``VIDIOCGFREQ`` and ``VIDIOCSFREQ`` ioctl to change the tuner
frequency where renamed to
-:ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
+:ref:`VIDIOC_G_FREQUENCY` and
:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>`. They take a pointer
to a struct :ref:`v4l2_frequency <v4l2-frequency>` instead of an
unsigned long integer.
V4L2 has no equivalent of the ``VIDIOCGPICT`` and ``VIDIOCSPICT`` ioctl
and struct :c:type:`struct video_picture`. The following fields where
replaced by V4L2 controls accessible with the
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>`,
-:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
+:ref:`VIDIOC_QUERYCTRL`,
+:ref:`VIDIOC_G_CTRL` and
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls:
The V4L picture controls are assumed to range from 0 to 65535 with no
particular reset value. The V4L2 API permits arbitrary limits and
defaults which can be queried with the
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` ioctl. For general
+:ref:`VIDIOC_QUERYCTRL` ioctl. For general
information about controls see :ref:`control`.
The ``depth`` (average number of bits per pixel) of a video image is
The ``VIDIOCGAUDIO`` and ``VIDIOCSAUDIO`` ioctl and struct
:c:type:`struct video_audio` are used to enumerate the audio inputs
of a V4L device. The equivalent V4L2 ioctls are
-:ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` and
+:ref:`VIDIOC_G_AUDIO` and
:ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` using struct
:ref:`v4l2_audio <v4l2-audio>` as discussed in :ref:`audio`.
stereo input, regardless if the source is a tuner.
The following fields where replaced by V4L2 controls accessible with the
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>`,
-:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
+:ref:`VIDIOC_QUERYCTRL`,
+:ref:`VIDIOC_G_CTRL` and
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls:
To determine which of these controls are supported by a driver V4L
provides the ``flags`` ``VIDEO_AUDIO_VOLUME``, ``VIDEO_AUDIO_BASS``,
``VIDEO_AUDIO_TREBLE`` and ``VIDEO_AUDIO_BALANCE``. In the V4L2 API the
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` ioctl reports if the
+:ref:`VIDIOC_QUERYCTRL` ioctl reports if the
respective control is supported. Accordingly the ``VIDEO_AUDIO_MUTABLE``
and ``VIDEO_AUDIO_MUTE`` flags where replaced by the boolean
``V4L2_CID_AUDIO_MUTE`` control.
:c:type:`struct video_audio` ``step`` field. The V4L audio controls
are assumed to range from 0 to 65535 with no particular reset value. The
V4L2 API permits arbitrary limits and defaults which can be queried with
-the :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` ioctl. For general
+the :ref:`VIDIOC_QUERYCTRL` ioctl. For general
information about controls see :ref:`control`.
====================
The V4L2 ioctls equivalent to ``VIDIOCGFBUF`` and ``VIDIOCSFBUF`` are
-:ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` and
+:ref:`VIDIOC_G_FBUF` and
:ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`. The ``base`` field of struct
:c:type:`struct video_buffer` remained unchanged, except V4L2 defines
a flag to indicate non-destructive overlays instead of a ``NULL``
Instead of the special ioctls ``VIDIOCGWIN`` and ``VIDIOCSWIN`` V4L2
uses the general-purpose data format negotiation ioctls
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+:ref:`VIDIOC_G_FMT` and
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`. They take a pointer to a struct
:ref:`v4l2_format <v4l2-format>` as argument. Here the ``win`` member
of the ``fmt`` union is used, a struct
size is determined by ``w.width`` and ``w.height``.
The ``VIDIOCCAPTURE`` ioctl to enable or disable overlay was renamed to
-:ref:`VIDIOC_OVERLAY <VIDIOC_OVERLAY>`.
+:ref:`VIDIOC_OVERLAY`.
Cropping
To capture only a subsection of the full picture V4L defines the
``VIDIOCGCAPTURE`` and ``VIDIOCSCAPTURE`` ioctls using struct
:c:type:`struct video_capture`. The equivalent V4L2 ioctls are
-:ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` and
+:ref:`VIDIOC_G_CROP` and
:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` using struct
:ref:`v4l2_crop <v4l2-crop>`, and the related
-:ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>` ioctl. This is a rather
+:ref:`VIDIOC_CROPCAP` ioctl. This is a rather
complex matter, see :ref:`crop` for details.
The ``x``, ``y``, ``width`` and ``height`` fields moved into struct
V4L2 device using the :ref:`read() <func-read>` function, however V4L2
drivers are not required to support this I/O method. Applications can
determine if the function is available with the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. All V4L2 devices
+:ref:`VIDIOC_QUERYCAP` ioctl. All V4L2 devices
exchanging data with applications must support the
:ref:`select() <func-select>` and :ref:`poll() <func-poll>`
functions.
To select an image format and size, V4L provides the ``VIDIOCSPICT`` and
``VIDIOCSWIN`` ioctls. V4L2 uses the general-purpose data format
-negotiation ioctls :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+negotiation ioctls :ref:`VIDIOC_G_FMT` and
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`. They take a pointer to a struct
:ref:`v4l2_format <v4l2-format>` as argument, here the struct
:ref:`v4l2_pix_format <v4l2-pix-format>` named ``pix`` of its
into the driver, unless it has a module option to change the
number when the driver module is loaded.
- - The :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl allocates the
+ - The :ref:`VIDIOC_REQBUFS` ioctl allocates the
desired number of buffers, this is a required step in the
initialization sequence.
- Buffers are individually mapped. The offset and size of each
buffer can be determined with the
- :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl.
+ :ref:`VIDIOC_QUERYBUF` ioctl.
- .. row 5
buffer has been filled.
- Drivers maintain an incoming and outgoing queue.
- :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` enqueues any empty buffer into
+ :ref:`VIDIOC_QBUF` enqueues any empty buffer into
the incoming queue. Filled buffers are dequeued from the outgoing
queue with the :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. To wait
until filled buffers become available this function,
:ref:`select() <func-select>` or :ref:`poll() <func-poll>` can
- be used. The :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` ioctl
+ be used. The :ref:`VIDIOC_STREAMON` ioctl
must be called once after enqueuing one or more buffers to start
capturing. Its counterpart
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` stops capturing and
dequeues all buffers from both queues. Applications can query the
signal status, if known, with the
- :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` ioctl.
+ :ref:`VIDIOC_ENUMINPUT` ioctl.
For a more in-depth discussion of memory mapping and examples, see
Input and output devices support the streaming I/O method when the
``V4L2_CAP_STREAMING`` flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl is set. Whether
+:ref:`VIDIOC_QUERYCAP` ioctl is set. Whether
importing DMA buffers through DMABUF file descriptors is supported is
-determined by calling the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`
+determined by calling the :ref:`VIDIOC_REQBUFS`
ioctl with the memory type set to ``V4L2_MEMORY_DMABUF``.
This I/O method is dedicated to sharing DMA buffers between different
are passed in struct :ref:`v4l2_buffer <v4l2-buffer>` (or in struct
:ref:`v4l2_plane <v4l2-plane>` in the multi-planar API case). The
driver must be switched into DMABUF I/O mode by calling the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` with the desired buffer type.
+:ref:`VIDIOC_REQBUFS` with the desired buffer type.
.. code-block:: c
}
The buffer (plane) file descriptor is passed on the fly with the
-:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. In case of multiplanar
+:ref:`VIDIOC_QBUF` ioctl. In case of multiplanar
buffers, every plane can be associated with a different DMABUF
descriptor. Although buffers are commonly cycled, applications can pass
a different DMABUF descriptor at each ``VIDIOC_QBUF`` call.
buffer at any time between the completion of the DMA and this ioctl. The
memory is also unlocked when
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` is called,
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`, or when the device is closed.
+:ref:`VIDIOC_REQBUFS`, or when the device is closed.
For capturing applications it is customary to enqueue a number of empty
buffers, to start capturing and enter the read loop. Here the
functions are always available.
To start and stop capturing or displaying applications call the
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
+:ref:`VIDIOC_STREAMON` and
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctls. Note that
``VIDIOC_STREAMOFF`` removes all buffers from both queues and unlocks
all buffers as a side effect. Since there is no notion of doing anything
To enumerate and query the attributes of the DV timings supported by a
device applications use the
-:ref:`VIDIOC_ENUM_DV_TIMINGS <VIDIOC_ENUM_DV_TIMINGS>` and
-:ref:`VIDIOC_DV_TIMINGS_CAP <VIDIOC_DV_TIMINGS_CAP>` ioctls. To set
+:ref:`VIDIOC_ENUM_DV_TIMINGS` and
+:ref:`VIDIOC_DV_TIMINGS_CAP` ioctls. To set
DV timings for the device applications use the
:ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl and to get
current DV timings they use the
-:ref:`VIDIOC_G_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl. To detect
+:ref:`VIDIOC_G_DV_TIMINGS` ioctl. To detect
the DV timings as seen by the video receiver applications use the
-:ref:`VIDIOC_QUERY_DV_TIMINGS <VIDIOC_QUERY_DV_TIMINGS>` ioctl.
+:ref:`VIDIOC_QUERY_DV_TIMINGS` ioctl.
Applications can make use of the :ref:`input-capabilities` and
:ref:`output-capabilities` flags to determine whether the digital
========================
Three new ioctls are available:
-:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
+:ref:`VIDIOC_G_EXT_CTRLS`,
:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`. These ioctls act
on arrays of controls (as opposed to the
-:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
+:ref:`VIDIOC_G_CTRL` and
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls that act on a single
control). This is needed since it is often required to atomically change
several controls at once.
Since such compound controls need to expose more information about
themselves than is possible with
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` the
+:ref:`VIDIOC_QUERYCTRL` the
:ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>` ioctl was added. In
particular, this ioctl gives the dimensions of the N-dimensional array
if this control consists of more than one element.
It is important to realize that due to the flexibility of controls it is
necessary to check whether the control you want to set actually is
supported in the driver and what the valid range of values is. So use
-the :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` (or
+the :ref:`VIDIOC_QUERYCTRL` (or
:ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`) and
:ref:`VIDIOC_QUERYMENU <VIDIOC_QUERYCTRL>` ioctls to check this. Also
note that it is possible that some of the menu indices in a control of
=============================
The recommended way to enumerate over the extended controls is by using
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` in combination with the
+:ref:`VIDIOC_QUERYCTRL` in combination with the
``V4L2_CTRL_FLAG_NEXT_CTRL`` flag:
The flags field of struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` also
contains hints on the behavior of the control. See the
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` documentation for more
+:ref:`VIDIOC_QUERYCTRL` documentation for more
details.
``V4L2_CID_MPEG_CLASS (class)``
The Codec class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class. This description can be
used as the caption of a Tab page in a GUI, for example.
This read-only control returns the 33-bit video Presentation Time
Stamp as defined in ITU T-REC-H.222.0 and ISO/IEC 13818-1 of the
currently displayed frame. This is the same PTS as is used in
- :ref:`VIDIOC_DECODER_CMD <VIDIOC_DECODER_CMD>`.
+ :ref:`VIDIOC_DECODER_CMD`.
.. _`v4l2-mpeg-video-dec-frame`:
``V4L2_CID_CAMERA_CLASS (class)``
The Camera class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class.
.. _`v4l2-exposure-auto-type`:
``V4L2_CID_FM_TX_CLASS (class)``
The FM_TX class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class.
``V4L2_CID_RDS_TX_DEVIATION (integer)``
``V4L2_CID_JPEG_CLASS (class)``
The JPEG class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class.
``V4L2_CID_JPEG_CHROMA_SUBSAMPLING (menu)``
``V4L2_CID_FM_RX_CLASS (class)``
The FM_RX class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class.
``V4L2_CID_RDS_RECEPTION (boolean)``
``V4L2_CID_DETECT_CLASS (class)``
The Detect class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class.
``V4L2_CID_DETECT_MD_MODE (menu)``
``V4L2_CID_RF_TUNER_CLASS (class)``
The RF_TUNER class descriptor. Calling
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` for this control will
+ :ref:`VIDIOC_QUERYCTRL` for this control will
return a description of this control class.
``V4L2_CID_RF_TUNER_BANDWIDTH_AUTO (boolean)``
A single mechanism exists to negotiate all data formats using the
aggregate struct :ref:`v4l2_format <v4l2-format>` and the
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+:ref:`VIDIOC_G_FMT` and
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls. Additionally the
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl can be used to examine
what the hardware *could* do, without actually selecting a new data
When applications omit the ``VIDIOC_S_FMT`` ioctl its locking side
effects are implied by the next step, the selection of an I/O method
-with the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl or implicit
+with the :ref:`VIDIOC_REQBUFS` ioctl or implicit
with the first :ref:`read() <func-read>` or
:ref:`write() <func-write>` call.
enumerate all image formats supported by video capture, overlay or
output devices is available. [1]_
-The :ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` ioctl must be supported
+The :ref:`VIDIOC_ENUM_FMT` ioctl must be supported
by all drivers exchanging image data with applications.
**Important**
address is a hint only, and is usually specified as 0.
Suitable length and offset parameters are queried with the
-:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl. Buffers must be
-allocated with the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl
+:ref:`VIDIOC_QUERYBUF` ioctl. Buffers must be
+allocated with the :ref:`VIDIOC_REQBUFS` ioctl
before they can be queried.
To unmap buffers the :ref:`munmap() <func-munmap>` function is used.
The ``flags`` or ``prot`` value is not supported.
No buffers have been allocated with the
- :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl.
+ :ref:`VIDIOC_REQBUFS` ioctl.
ENOMEM
Not enough physical or virtual memory was available to complete the
buffer has been filled by the capture device and can be dequeued with
the :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. For output devices this
function waits until the device is ready to accept a new buffer to be
-queued up with the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl for
+queued up with the :ref:`VIDIOC_QBUF` ioctl for
display. When buffers are already in the outgoing queue of the driver
(capture) or the incoming queue isn't full (display) the function
returns immediately.
``POLLWRNORM`` flags. When the function timed out it returns a value of
zero, on failure it returns -1 and the ``errno`` variable is set
appropriately. When the application did not call
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` the :c:func:`poll()`
+:ref:`VIDIOC_STREAMON` the :c:func:`poll()`
function succeeds, but sets the ``POLLERR`` flag in the ``revents``
field. When the application has called
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` for a capture device but
-hasn't yet called :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`, the
+:ref:`VIDIOC_STREAMON` for a capture device but
+hasn't yet called :ref:`VIDIOC_QBUF`, the
:c:func:`poll()` function succeeds and sets the ``POLLERR`` flag in
the ``revents`` field. For output devices this same situation will cause
:c:func:`poll()` to succeed as well, but it sets the ``POLLOUT`` and
``POLLWRNORM`` flags in the ``revents`` field.
-If an event occurred (see :ref:`VIDIOC_DQEVENT <VIDIOC_DQEVENT>`)
+If an event occurred (see :ref:`VIDIOC_DQEVENT`)
then ``POLLPRI`` will be set in the ``revents`` field and
:c:func:`poll()` will return.
depends on the discarding policy.
Applications can get and set the number of buffers used internally by
-the driver with the :ref:`VIDIOC_G_PARM <VIDIOC_G_PARM>` and
+the driver with the :ref:`VIDIOC_G_PARM` and
:ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctls. They are optional,
however. The discarding policy is not reported and cannot be changed.
For minimum requirements see :ref:`devices`.
the :c:type:`struct fd_set`s. When the function timed out it returns
a value of zero. On failure it returns -1 and the ``errno`` variable is
set appropriately. When the application did not call
-:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` or
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` yet the :c:func:`select()`
+:ref:`VIDIOC_QBUF` or
+:ref:`VIDIOC_STREAMON` yet the :c:func:`select()`
function succeeds, setting the bit of the file descriptor in ``readfds``
or ``writefds``, but subsequent :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`
calls will fail. [1]_
1998-10-02: The ``id`` field was removed from struct
:c:type:`struct video_standard` and the color subcarrier fields were
-renamed. The :ref:`VIDIOC_QUERYSTD <VIDIOC_QUERYSTD>` ioctl was
-renamed to :ref:`VIDIOC_ENUMSTD <VIDIOC_ENUMSTD>`,
-:ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` to
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>`. A first draft of the
+renamed. The :ref:`VIDIOC_QUERYSTD` ioctl was
+renamed to :ref:`VIDIOC_ENUMSTD`,
+:ref:`VIDIOC_G_INPUT` to
+:ref:`VIDIOC_ENUMINPUT`. A first draft of the
Codec API was released.
1998-11-08: Many minor changes. Most symbols have been renamed. Some
1998-11-14: ``V4L2_PIX_FMT_RGB24`` changed to ``V4L2_PIX_FMT_BGR24``,
and ``V4L2_PIX_FMT_RGB32`` changed to ``V4L2_PIX_FMT_BGR32``. Audio
controls are now accessible with the
-:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
+:ref:`VIDIOC_G_CTRL` and
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls under names starting
with ``V4L2_CID_AUDIO``. The ``V4L2_MAJOR`` define was removed from
``videodev.h`` since it was only used once in the ``videodev`` kernel
int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a);
4. All the different get- and set-format commands were swept into one
- :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+ :ref:`VIDIOC_G_FMT` and
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl taking a union and a
type field selecting the union member as parameter. Purpose is to
simplify the API by eliminating several ioctls and to allow new and
2001-04-13: Big endian 16-bit RGB formats were added.
2001-09-17: New YUV formats and the
-:ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
+:ref:`VIDIOC_G_FREQUENCY` and
:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctls were added.
(The old ``VIDIOC_G_FREQ`` and ``VIDIOC_S_FREQ`` ioctls did not take
multiple tuners into account.)
2000-09-18: ``V4L2_BUF_TYPE_VBI`` was added. This may *break
-compatibility* as the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+compatibility* as the :ref:`VIDIOC_G_FMT` and
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls may fail now if the struct
:c:type:`struct v4l2_fmt` ``type`` field does not contain
``V4L2_BUF_TYPE_VBI``. In the documentation of the struct
dramatically. Note that also the size of the structure changed,
which is encoded in the ioctl request code, thus older V4L2 devices
will respond with an EINVAL error code to the new
- :ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl.
+ :ref:`VIDIOC_QUERYCAP` ioctl.
There are new fields to identify the driver, a new RDS device
function ``V4L2_CAP_RDS_CAPTURE``, the ``V4L2_CAP_AUDIO`` flag
supported standards with an ioctl applications can now refer to
standards by :ref:`v4l2_std_id <v4l2-std-id>` and symbols
defined in the ``videodev2.h`` header file. For details see
- :ref:`standard`. The :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and
+ :ref:`standard`. The :ref:`VIDIOC_G_STD` and
:ref:`VIDIOC_S_STD <VIDIOC_G_STD>` now take a pointer to this
- type as argument. :ref:`VIDIOC_QUERYSTD <VIDIOC_QUERYSTD>` was
+ type as argument. :ref:`VIDIOC_QUERYSTD` was
added to autodetect the received standard, if the hardware has this
capability. In struct :ref:`v4l2_standard <v4l2-standard>` an
``index`` field was added for
- :ref:`VIDIOC_ENUMSTD <VIDIOC_ENUMSTD>`. A
+ :ref:`VIDIOC_ENUMSTD`. A
:ref:`v4l2_std_id <v4l2-std-id>` field named ``id`` was added as
machine readable identifier, also replacing the ``transmission``
field. The misleading ``framerate`` field was renamed to
removed.
Struct :c:type:`struct v4l2_enumstd` ceased to be.
- :ref:`VIDIOC_ENUMSTD <VIDIOC_ENUMSTD>` now takes a pointer to a
+ :ref:`VIDIOC_ENUMSTD` now takes a pointer to a
struct :ref:`v4l2_standard <v4l2-standard>` directly. The
information which standards are supported by a particular video
input or output moved into struct :ref:`v4l2_input <v4l2-input>`
added as in struct :ref:`v4l2_format <v4l2-format>`. The
``VIDIOC_ENUM_FBUFFMT`` ioctl is no longer needed and was removed.
These calls can be replaced by
- :ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` with type
+ :ref:`VIDIOC_ENUM_FMT` with type
``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
11. In struct :ref:`v4l2_pix_format <v4l2-pix-format>` the ``depth``
3. The audio input and output interface was found to be incomplete.
- Previously the :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl would
+ Previously the :ref:`VIDIOC_G_AUDIO` ioctl would
enumerate the available audio inputs. An ioctl to determine the
current audio input, if more than one combines with the current video
input, did not exist. So ``VIDIOC_G_AUDIO`` was renamed to
``VIDIOC_G_AUDIO_OLD``, this ioctl was removed on Kernel 2.6.39. The
- :ref:`VIDIOC_ENUMAUDIO <VIDIOC_ENUMAUDIO>` ioctl was added to
+ :ref:`VIDIOC_ENUMAUDIO` ioctl was added to
enumerate audio inputs, while
- :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` now reports the current
+ :ref:`VIDIOC_G_AUDIO` now reports the current
audio input.
The same changes were made to
between the old and new ioctls, but drivers and applications must be
updated to successfully compile again.
-4. The :ref:`VIDIOC_OVERLAY <VIDIOC_OVERLAY>` ioctl was incorrectly
+4. The :ref:`VIDIOC_OVERLAY` ioctl was incorrectly
defined with write-read parameter. It was changed to write-only,
while the write-read version was renamed to ``VIDIOC_OVERLAY_OLD``.
The old ioctl was removed on Kernel 2.6.39. Until further the
V4L2 in Linux 2.6.6, 2004-05-09
===============================
-1. The :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>` ioctl was incorrectly
+1. The :ref:`VIDIOC_CROPCAP` ioctl was incorrectly
defined with read-only parameter. It is now defined as write-read
ioctl, while the read-only version was renamed to
``VIDIOC_CROPCAP_OLD``. The old ioctl was removed on Kernel 2.6.39.
3. In the Current Audio Input example the ``VIDIOC_G_AUDIO`` ioctl took
the wrong argument.
-4. The documentation of the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` and
+4. The documentation of the :ref:`VIDIOC_QBUF` and
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctls did not mention the
struct :ref:`v4l2_buffer <v4l2-buffer>` ``memory`` field. It was
also missing from examples. Also on the ``VIDIOC_DQBUF`` page the EIO
V4L2 in Linux 2.6.15
====================
-1. The :ref:`VIDIOC_LOG_STATUS <VIDIOC_LOG_STATUS>` ioctl was added.
+1. The :ref:`VIDIOC_LOG_STATUS` ioctl was added.
2. New video standards ``V4L2_STD_NTSC_443``, ``V4L2_STD_SECAM_LC``,
``V4L2_STD_SECAM_DK`` (a set of SECAM D, K and K1), and
2. A new ``V4L2_TUNER_MODE_LANG1_LANG2`` was defined to record both
languages of a bilingual program. The use of
``V4L2_TUNER_MODE_STEREO`` for this purpose is deprecated now. See
- the :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` section for details.
+ the :ref:`VIDIOC_G_TUNER` section for details.
V4L2 spec erratum 2006-09-23 (Draft 0.15)
V4L2 in Linux 2.6.18
====================
-1. New ioctls :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
+1. New ioctls :ref:`VIDIOC_G_EXT_CTRLS`,
:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` were added, a
flag to skip unsupported controls with
- :ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>`, new control types
+ :ref:`VIDIOC_QUERYCTRL`, new control types
``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_TYPE_CTRL_CLASS``
(:ref:`v4l2-ctrl-type`), and new control flags
``V4L2_CTRL_FLAG_READ_ONLY``, ``V4L2_CTRL_FLAG_UPDATE``,
buffer type field was added replacing a reserved field. Note on
architectures where the size of enum types differs from int types the
size of the structure changed. The
- :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl
+ :ref:`VIDIOC_G_SLICED_VBI_CAP` ioctl
was redefined from being read-only to write-read. Applications must
initialize the type field and clear the reserved fields now. These
changes may *break the compatibility* with older drivers and
applications.
-2. The ioctls :ref:`VIDIOC_ENUM_FRAMESIZES <VIDIOC_ENUM_FRAMESIZES>`
+2. The ioctls :ref:`VIDIOC_ENUM_FRAMESIZES`
and
- :ref:`VIDIOC_ENUM_FRAMEINTERVALS <VIDIOC_ENUM_FRAMEINTERVALS>`
+ :ref:`VIDIOC_ENUM_FRAMEINTERVALS`
were added.
3. A new pixel format ``V4L2_PIX_FMT_RGB444`` (:ref:`rgb-formats`) was
2. Three new clipping/blending methods with a global or straight or
inverted local alpha value were added to the video overlay interface.
- See the description of the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
+ See the description of the :ref:`VIDIOC_G_FBUF`
and :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` ioctls for details.
A new ``global_alpha`` field was added to
V4L2 in Linux 2.6.27
====================
-1. The :ref:`VIDIOC_S_HW_FREQ_SEEK <VIDIOC_S_HW_FREQ_SEEK>` ioctl
+1. The :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
and the ``V4L2_CAP_HW_FREQ_SEEK`` capability were added.
2. The pixel formats ``V4L2_PIX_FMT_YVYU``, ``V4L2_PIX_FMT_PCA501``,
1. Added :ref:`JPEG compression control class <jpeg-controls>`.
2. Extended the DV Timings API:
- :ref:`VIDIOC_ENUM_DV_TIMINGS <VIDIOC_ENUM_DV_TIMINGS>`,
- :ref:`VIDIOC_QUERY_DV_TIMINGS <VIDIOC_QUERY_DV_TIMINGS>` and
- :ref:`VIDIOC_DV_TIMINGS_CAP <VIDIOC_DV_TIMINGS_CAP>`.
+ :ref:`VIDIOC_ENUM_DV_TIMINGS`,
+ :ref:`VIDIOC_QUERY_DV_TIMINGS` and
+ :ref:`VIDIOC_DV_TIMINGS_CAP`.
V4L2 in Linux 3.5
V4L2_CTRL_TYPE_INTEGER_MENU.
2. Added selection API for V4L2 subdev interface:
- :ref:`VIDIOC_SUBDEV_G_SELECTION <VIDIOC_SUBDEV_G_SELECTION>` and
+ :ref:`VIDIOC_SUBDEV_G_SELECTION` and
:ref:`VIDIOC_SUBDEV_S_SELECTION <VIDIOC_SUBDEV_G_SELECTION>`.
3. Added ``V4L2_COLORFX_ANTIQUE``, ``V4L2_COLORFX_ART_FREEZE``,
capabilities.
3. Added support for frequency band enumerations:
- :ref:`VIDIOC_ENUM_FREQ_BANDS <VIDIOC_ENUM_FREQ_BANDS>`.
+ :ref:`VIDIOC_ENUM_FREQ_BANDS`.
V4L2 in Linux 3.9
capability flags V4L2_IN_CAP_PRESETS and V4L2_OUT_CAP_PRESETS.
2. Added new debugging ioctl
- :ref:`VIDIOC_DBG_G_CHIP_INFO <VIDIOC_DBG_G_CHIP_INFO>`.
+ :ref:`VIDIOC_DBG_G_CHIP_INFO`.
V4L2 in Linux 3.11
The following V4L2 API elements are currently experimental and may
change in the future.
-- :ref:`VIDIOC_DBG_G_REGISTER <VIDIOC_DBG_G_REGISTER>` and
+- :ref:`VIDIOC_DBG_G_REGISTER` and
:ref:`VIDIOC_DBG_S_REGISTER <VIDIOC_DBG_G_REGISTER>` ioctls.
-- :ref:`VIDIOC_DBG_G_CHIP_INFO <VIDIOC_DBG_G_CHIP_INFO>` ioctl.
+- :ref:`VIDIOC_DBG_G_CHIP_INFO` ioctl.
.. _obsolete:
Other methods must be negotiated. To select the streaming I/O method
with memory mapped or user buffers applications call the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl. The asynchronous I/O
+:ref:`VIDIOC_REQBUFS` ioctl. The asynchronous I/O
method is not defined yet.
Video overlay can be considered another I/O method, although the
In most cases, libv4l2 just passes the calls directly through to the
v4l2 driver, intercepting the calls to
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>`,
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`
+:ref:`VIDIOC_G_FMT`
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`
-:ref:`VIDIOC_ENUM_FRAMESIZES <VIDIOC_ENUM_FRAMESIZES>` and
-:ref:`VIDIOC_ENUM_FRAMEINTERVALS <VIDIOC_ENUM_FRAMEINTERVALS>` in
+:ref:`VIDIOC_ENUM_FRAMESIZES` and
+:ref:`VIDIOC_ENUM_FRAMEINTERVALS` in
order to emulate the formats
:ref:`V4L2_PIX_FMT_BGR24 <V4L2-PIX-FMT-BGR24>`,
:ref:`V4L2_PIX_FMT_RGB24 <V4L2-PIX-FMT-RGB24>`,
:ref:`V4L2_PIX_FMT_YUV420 <V4L2-PIX-FMT-YUV420>`, and
:ref:`V4L2_PIX_FMT_YVU420 <V4L2-PIX-FMT-YVU420>`, if they aren't
-available in the driver. :ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>`
+available in the driver. :ref:`VIDIOC_ENUM_FMT`
keeps enumerating the hardware supported formats, plus the emulated
formats offered by libv4l at the end.
Input and output devices support this I/O method when the
``V4L2_CAP_STREAMING`` flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl is set. There are two
+:ref:`VIDIOC_QUERYCAP` ioctl is set. There are two
streaming methods, to determine if the memory mapping flavor is
supported applications must call the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl.
+:ref:`VIDIOC_REQBUFS` ioctl.
Streaming is an I/O method where only pointers to buffers are exchanged
between application and driver, the data itself is not copied. Memory
different file descriptors must be used. [1]_
To allocate device buffers applications call the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl with the desired number
+:ref:`VIDIOC_REQBUFS` ioctl with the desired number
of buffers and buffer type, for example ``V4L2_BUF_TYPE_VIDEO_CAPTURE``.
This ioctl can also be used to change the number of buffers or to free
the allocated memory, provided none of the buffers are still mapped.
Before applications can access the buffers they must map them into their
address space with the :ref:`mmap() <func-mmap>` function. The
location of the buffers in device memory can be determined with the
-:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl. In the single-planar
+:ref:`VIDIOC_QUERYBUF` ioctl. In the single-planar
API case, the ``m.offset`` and ``length`` returned in a struct
:ref:`v4l2_buffer <v4l2-buffer>` are passed as sixth and second
parameter to the :c:func:`mmap()` function. When using the
empty buffer can be dequeued and reused.
To enqueue and dequeue a buffer applications use the
-:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` and
+:ref:`VIDIOC_QBUF` and
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. The status of a buffer being
mapped, enqueued, full or empty can be determined at any time using the
-:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl. Two methods exist to
+:ref:`VIDIOC_QUERYBUF` ioctl. Two methods exist to
suspend execution of the application until one or more buffers can be
dequeued. By default ``VIDIOC_DQBUF`` blocks when no buffer is in the
outgoing queue. When the ``O_NONBLOCK`` flag was given to the
are always available.
To start and stop capturing or output applications call the
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
+:ref:`VIDIOC_STREAMON` and
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctl. Note
``VIDIOC_STREAMOFF`` removes all buffers from both queues as a side
effect. Since there is no notion of doing anything "now" on a
.. [1]
One could use one file descriptor and set the buffer type field
- accordingly when calling :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` etc.,
+ accordingly when calling :ref:`VIDIOC_QBUF` etc.,
but it makes the :c:func:`select()` function ambiguous. We also
like the clean approach of one file descriptor per logical stream.
Video overlay for example is also a logical stream, although the CPU
device should not change the state of the device. [2]_
Once an application has allocated the memory buffers needed for
-streaming data (by calling the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`
-or :ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>` ioctls, or
+streaming data (by calling the :ref:`VIDIOC_REQBUFS`
+or :ref:`VIDIOC_CREATE_BUFS` ioctls, or
implicitly by calling the :ref:`read() <func-read>` or
:ref:`write() <func-write>` functions) that application (filehandle)
becomes the owner of the device. It is no longer allowed to make changes
- 'JPEG'
- - TBD. See also :ref:`VIDIOC_G_JPEGCOMP <VIDIOC_G_JPEGCOMP>`,
+ - TBD. See also :ref:`VIDIOC_G_JPEGCOMP`,
:ref:`VIDIOC_S_JPEGCOMP <VIDIOC_G_JPEGCOMP>`.
- .. _`V4L2-PIX-FMT-MPEG`:
The XRGB and XBGR formats contain undefined bits (-). Applications,
devices and drivers must ignore those bits, for both
-:ref:`capture <capture>` and :ref:`output <output>` devices.
+:ref:`capture` and :ref:`output` devices.
**Byte Order..**
version (see :ref:`planar-apis`). Image formats are negotiated with
the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. (The explanations here
focus on video capturing and output, for overlay frame buffer formats
-see also :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`.)
+see also :ref:`VIDIOC_G_FBUF`.)
.. toctree::
Calls that distinguish between single and multi-planar APIs
===========================================================
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>`
+:ref:`VIDIOC_QUERYCAP`
Two additional multi-planar capabilities are added. They can be set
together with non-multi-planar ones for devices that handle both
single- and multi-planar formats.
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`,
+:ref:`VIDIOC_G_FMT`,
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`,
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>`
New structures for describing multi-planar formats are added: struct
Drivers may define new multi-planar formats, which have distinct
FourCC codes from the existing single-planar ones.
-:ref:`VIDIOC_QBUF <VIDIOC_QBUF>`,
+:ref:`VIDIOC_QBUF`,
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`,
-:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`
+:ref:`VIDIOC_QUERYBUF`
A new struct :ref:`v4l2_plane <v4l2-plane>` structure for
describing planes is added. Arrays of this structure are passed in
the new ``m.planes`` field of struct
:ref:`v4l2_buffer <v4l2-buffer>`.
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`
+:ref:`VIDIOC_REQBUFS`
Will allocate multi-planar buffers as requested.
the same type have different capabilities and this specification permits
the omission of a few complicated and less important parts of the API.
-The :ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl is available to
+The :ref:`VIDIOC_QUERYCAP` ioctl is available to
check if the kernel device is compatible with this specification, and to
query the :ref:`functions <devices>` and :ref:`I/O methods <io>`
supported by the device.
-Starting with kernel version 3.1, :ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>`
+Starting with kernel version 3.1, :ref:`VIDIOC_QUERYCAP`
will return the V4L2 API version used by the driver, with generally
matches the Kernel version. There's no need of using
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` to check if a specific ioctl
+:ref:`VIDIOC_QUERYCAP` to check if a specific ioctl
is supported, the V4L2 core now returns ENOTTY if a driver doesn't
provide support for an ioctl.
Other features can be queried by calling the respective ioctl, for
-example :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` to learn about the
+example :ref:`VIDIOC_ENUMINPUT` to learn about the
number, types and names of video connectors on the device. Although
abstraction is a major objective of this API, the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl also allows driver
+:ref:`VIDIOC_QUERYCAP` ioctl also allows driver
specific applications to reliably identify the driver.
-All V4L2 drivers must support :ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>`.
+All V4L2 drivers must support :ref:`VIDIOC_QUERYCAP`.
Applications should always call this ioctl after opening the device.
:c:func:`write()` function, respectively, when the
``V4L2_CAP_READWRITE`` flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl is set.
+:ref:`VIDIOC_QUERYCAP` ioctl is set.
Drivers may need the CPU to copy the data, but they may also support DMA
to or from user memory, so this I/O method is not necessarily less
set of standards. This set is reported by the ``std`` field of struct
:ref:`v4l2_input <v4l2-input>` and struct
:ref:`v4l2_output <v4l2-output>` returned by the
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` and
-:ref:`VIDIOC_ENUMOUTPUT <VIDIOC_ENUMOUTPUT>` ioctls, respectively.
+:ref:`VIDIOC_ENUMINPUT` and
+:ref:`VIDIOC_ENUMOUTPUT` ioctls, respectively.
V4L2 defines one bit for each analog video standard currently in use
worldwide, and sets aside bits for driver defined standards, e. g.
Applications can use the predefined bits to select a particular
standard, although presenting the user a menu of supported standards is
preferred. To enumerate and query the attributes of the supported
-standards applications use the :ref:`VIDIOC_ENUMSTD <VIDIOC_ENUMSTD>`
+standards applications use the :ref:`VIDIOC_ENUMSTD`
ioctl.
Many of the defined standards are actually just variations of a few
"NTSC-M" and "SECAM-D/K". [1]_
To query and select the standard used by the current video input or
-output applications call the :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and
+output applications call the :ref:`VIDIOC_G_STD` and
:ref:`VIDIOC_S_STD <VIDIOC_G_STD>` ioctl, respectively. The
*received* standard can be sensed with the
-:ref:`VIDIOC_QUERYSTD <VIDIOC_QUERYSTD>` ioctl. Note that the
+:ref:`VIDIOC_QUERYSTD` ioctl. Note that 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
section discussing the :ref:`read() <func-read>` function.
To get and set the streaming parameters applications call the
-:ref:`VIDIOC_G_PARM <VIDIOC_G_PARM>` and
+:ref:`VIDIOC_G_PARM` and
:ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl, respectively. They take
a pointer to a struct :ref:`v4l2_streamparm <v4l2-streamparm>`, which
contains a union holding separate parameters for input and output
signal. Each tuner is associated with one or more video inputs,
depending on the number of RF connectors on the tuner. The ``type``
field of the respective struct :ref:`v4l2_input <v4l2-input>`
-returned by the :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` ioctl is
+returned by the :ref:`VIDIOC_ENUMINPUT` ioctl is
set to ``V4L2_INPUT_TYPE_TUNER`` and its ``tuner`` field contains the
index number of the tuner.
inputs.
To query and change tuner properties applications use the
-:ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` and
+:ref:`VIDIOC_G_TUNER` and
:ref:`VIDIOC_S_TUNER <VIDIOC_G_TUNER>` ioctls, respectively. The
struct :ref:`v4l2_tuner <v4l2-tuner>` returned by ``VIDIOC_G_TUNER``
also contains signal status information applicable when the tuner of the
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 <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl when the device has
+:ref:`VIDIOC_QUERYCAP` ioctl when the device has
one or more tuners.
video outputs, depending on the number of RF connectors on the
modulator. The ``type`` field of the respective struct
:ref:`v4l2_output <v4l2-output>` returned by the
-:ref:`VIDIOC_ENUMOUTPUT <VIDIOC_ENUMOUTPUT>` ioctl is set to
+:ref:`VIDIOC_ENUMOUTPUT` ioctl is set to
``V4L2_OUTPUT_TYPE_MODULATOR`` and its ``modulator`` field contains the
index number of the modulator.
cannot specify whether the frequency is for a tuner or a modulator.
To query and change modulator properties applications use the
-:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` and
+:ref:`VIDIOC_G_MODULATOR` and
:ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl. Note that
``VIDIOC_S_MODULATOR`` does not switch the current modulator, when there
is more than one at all. The modulator is solely determined by the
current video output. Drivers must support both ioctls and set the
``V4L2_CAP_MODULATOR`` flag in the struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl when the device has
+:ref:`VIDIOC_QUERYCAP` ioctl when the device has
one or more modulators.
===============
To get and set the tuner or modulator radio frequency applications use
-the :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
+the :ref:`VIDIOC_G_FREQUENCY` and
:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl which both take
a pointer to a struct :ref:`v4l2_frequency <v4l2-frequency>`. These
ioctls are used for TV and radio devices alike. Drivers must support
Input and output devices support this I/O method when the
``V4L2_CAP_STREAMING`` flag in the ``capabilities`` field of struct
:ref:`v4l2_capability <v4l2-capability>` returned by the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl is set. If the
+:ref:`VIDIOC_QUERYCAP` ioctl is set. If the
particular user pointer method (not only memory mapping) is supported
must be determined by calling the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl.
+:ref:`VIDIOC_REQBUFS` ioctl.
This I/O method combines advantages of the read/write and memory mapping
methods. Buffers (planes) are allocated by the application itself, and
struct :ref:`v4l2_buffer <v4l2-buffer>` (or in struct
:ref:`v4l2_plane <v4l2-plane>` in the multi-planar API case). The
driver must be switched into user pointer I/O mode by calling the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` with the desired buffer type.
+:ref:`VIDIOC_REQBUFS` with the desired buffer type.
No buffers (planes) are allocated beforehand, consequently they are not
indexed and cannot be queried like mapped buffers with the
``VIDIOC_QUERYBUF`` ioctl.
}
Buffer (plane) addresses and sizes are passed on the fly with the
-:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. Although buffers are commonly
+:ref:`VIDIOC_QBUF` ioctl. Although buffers are commonly
cycled, applications can pass different addresses and sizes at each
``VIDIOC_QBUF`` call. If required by the hardware the driver swaps
memory pages within physical memory to create a continuous area of
memory pages at any time between the completion of the DMA and this
ioctl. The memory is also unlocked when
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` is called,
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`, or when the device is closed.
+:ref:`VIDIOC_REQBUFS`, or when the device is closed.
Applications must take care not to free buffers without dequeuing. For
once, the buffers remain locked until further, wasting physical memory.
Second the driver will not be notified when the memory is returned to
are always available.
To start and stop capturing or output applications call the
-:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
+:ref:`VIDIOC_STREAMON` and
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctl. Note
``VIDIOC_STREAMOFF`` removes all buffers from both queues and unlocks
all buffers as a side effect. Since there is no notion of doing anything
To learn about the number and attributes of the available inputs and
outputs applications can enumerate them with the
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` and
-:ref:`VIDIOC_ENUMOUTPUT <VIDIOC_ENUMOUTPUT>` ioctl, respectively. The
+:ref:`VIDIOC_ENUMINPUT` and
+:ref:`VIDIOC_ENUMOUTPUT` ioctl, respectively. The
struct :ref:`v4l2_input <v4l2-input>` returned by the
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` ioctl also contains signal
+:ref:`VIDIOC_ENUMINPUT` ioctl also contains signal
:status information applicable when the current video input is queried.
-The :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and
-:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctls return the index of
+The :ref:`VIDIOC_G_INPUT` and
+:ref:`VIDIOC_G_OUTPUT` ioctls return the index of
the current video input or output. To select a different input or output
applications call the :ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>` and
:ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctls. Drivers must
This ioctl is used to create buffers for :ref:`memory mapped <mmap>`
or :ref:`user pointer <userp>` or :ref:`DMA buffer <dmabuf>` I/O. It
can be used as an alternative or in addition to the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl, when a tighter control
+:ref:`VIDIOC_REQBUFS` ioctl, when a tighter control
over buffers is required. This ioctl can be called multiple times to
create buffers of different sizes.
able to handle. The application has to fill in this struct
:ref:`v4l2_format <v4l2-format>`. Usually this will be done using the
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` or
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctls to ensure that the
+:ref:`VIDIOC_G_FMT` ioctls to ensure that the
requested format is supported by the driver. Based on the format's
``type`` field the requested buffer size (for single-planar) or plane
sizes (for multi-planar formats) will be used for the allocated buffers.
**Note**
- This is an :ref:`experimental <experimental>` interface and may
+ This is an :ref:`experimental` interface and may
change in the future.
For driver debugging purposes this ioctl allows test applications to
**Note**
- This is an :ref:`experimental <experimental>` interface and may
+ This is an :ref:`experimental` interface and may
change in the future.
For driver debugging purposes these ioctls allow test applications to
selects the nth non-sub-device chip on the TV card. The number zero
always selects the host chip, e. g. the chip connected to the PCI or USB
bus. You can find out which chips are present with the
-:ref:`VIDIOC_DBG_G_CHIP_INFO <VIDIOC_DBG_G_CHIP_INFO>` ioctl.
+:ref:`VIDIOC_DBG_G_CHIP_INFO` ioctl.
When ``match.type`` is ``V4L2_CHIP_MATCH_SUBDEV``, ``match.addr``
selects the nth sub-device.
These ioctls are optional, not all drivers may support them. However
when a driver supports these ioctls it must also support
-:ref:`VIDIOC_DBG_G_CHIP_INFO <VIDIOC_DBG_G_CHIP_INFO>`. Conversely
+:ref:`VIDIOC_DBG_G_CHIP_INFO`. Conversely
it may support ``VIDIOC_DBG_G_CHIP_INFO`` but not these ioctls.
``VIDIOC_DBG_G_REGISTER`` and ``VIDIOC_DBG_S_REGISTER`` were introduced
The ``cmd`` field must contain the command code. Some commands use the
``flags`` field for additional information.
-A :c:func:`write()`() or :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`
+A :c:func:`write()`() or :ref:`VIDIOC_STREAMON`
call sends an implicit START command to the decoder if it has not been
started yet.
- The 32-bit value of the control for 32-bit control types. This is
0 for string controls since the value of a string cannot be passed
- using :ref:`VIDIOC_DQEVENT <VIDIOC_DQEVENT>`.
+ using :ref:`VIDIOC_DQEVENT`.
- .. row 5
until the end of the current *Group Of Pictures*, otherwise it will stop
immediately.
-A :c:func:`read()`() or :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`
+A :c:func:`read()`() or :ref:`VIDIOC_STREAMON`
call sends an implicit START command to the encoder if it has not been
started yet. After a STOP command, :c:func:`read()`() calls will read
the remaining data buffered by the driver. When the buffer is empty,
While some DV receivers or transmitters support a wide range of timings,
others support only a limited number of timings. With this ioctl
applications can enumerate a list of known supported timings. Call
-:ref:`VIDIOC_DV_TIMINGS_CAP <VIDIOC_DV_TIMINGS_CAP>` to check if it
+:ref:`VIDIOC_DV_TIMINGS_CAP` to check if it
also supports other standards or even custom timings that are not in
this list.
device supports for the given pixel format and frame size.
The supported pixel formats and frame sizes can be obtained by using the
-:ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` and
-:ref:`VIDIOC_ENUM_FRAMESIZES <VIDIOC_ENUM_FRAMESIZES>` functions.
+:ref:`VIDIOC_ENUM_FMT` and
+:ref:`VIDIOC_ENUM_FRAMESIZES` functions.
The return value and the content of the ``v4l2_frmivalenum.type`` field
depend on the type of frame intervals the device supports. Here are the
format.
The supported pixel formats can be obtained by using the
-:ref:`VIDIOC_ENUM_FMT <VIDIOC_ENUM_FMT>` function.
+:ref:`VIDIOC_ENUM_FMT` function.
The return value and the content of the ``v4l2_frmsizeenum.type`` field
depend on the type of frame sizes the device supports. Here are the
method, therefore it is available only for ``V4L2_MEMORY_MMAP`` buffers.
It can be used to export a buffer as a DMABUF file at any time after
buffers have been allocated with the
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl.
+:ref:`VIDIOC_REQBUFS` ioctl.
To export a buffer, applications fill struct
:ref:`v4l2_exportbuffer <v4l2-exportbuffer>`. The ``type`` field is
:ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``type``.
Applications must also set the ``index`` field. Valid index numbers
range from zero to the number of buffers allocated with
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` (struct
+:ref:`VIDIOC_REQBUFS` (struct
:ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``count``) minus
one. For the multi-planar API, applications set the ``plane`` field to
the index of the plane to be exported. Valid planes range from zero to
- Number of the buffer, set by the application. This field is only
used for :ref:`memory mapping <mmap>` I/O and can range from
zero to the number of buffers allocated with the
- :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` and/or
- :ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>` ioctls.
+ :ref:`VIDIOC_REQBUFS` and/or
+ :ref:`VIDIOC_CREATE_BUFS` ioctls.
- .. row 3
Finally the driver programs the hardware with the actual cropping and
image parameters. ``VIDIOC_S_CROP`` is a write-only ioctl, it does not
return the actual parameters. To query them applications must call
-``VIDIOC_G_CROP`` and :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`. When the
+``VIDIOC_G_CROP`` and :ref:`VIDIOC_G_FMT`. When the
parameters are unsuitable the application may modify the cropping or
image parameters and repeat the cycle until satisfactory parameters have
been negotiated.
EINVAL error code is returned as well.
These ioctls work only with user controls. For other control classes the
-:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
+:ref:`VIDIOC_G_EXT_CTRLS`,
:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` or
:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` must be used.
The ``linux/v4l2-dv-timings.h`` header can be used to get the timings of
the formats in the :ref:`cea861` and :ref:`vesadmt` standards. If
the current input or output does not support DV timings (e.g. if
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` does not set the
+:ref:`VIDIOC_ENUMINPUT` does not set the
``V4L2_IN_CAP_DV_TIMINGS`` flag), then ENODATA error code is returned.
When used with video nodes the ``pad`` field represents the input (for
video capture devices) or output (for video output devices) index as is
-returned by :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` and
-:ref:`VIDIOC_ENUMOUTPUT <VIDIOC_ENUMOUTPUT>` respectively. When used
+returned by :ref:`VIDIOC_ENUMINPUT` and
+:ref:`VIDIOC_ENUMOUTPUT` respectively. When used
with subdevice nodes the ``pad`` field represents the input or output
pad of the subdevice. If there is no EDID support for the given ``pad``
value, then the EINVAL error code will be returned.
- Pad for which to get/set the EDID blocks. When used with a video
device node the pad represents the input or output index as
- returned by :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` and
- :ref:`VIDIOC_ENUMOUTPUT <VIDIOC_ENUMOUTPUT>` respectively.
+ returned by :ref:`VIDIOC_ENUMINPUT` and
+ :ref:`VIDIOC_ENUMOUTPUT` respectively.
- .. row 2
should re-allocate the memory to this new size and try again. For the
string type it is possible that the same issue occurs again if the
string has grown in the meantime. It is recommended to call
-:ref:`VIDIOC_QUERYCTRL <VIDIOC_QUERYCTRL>` first and use
+:ref:`VIDIOC_QUERYCTRL` first and use
``maximum``\ +1 as the new ``size`` value. It is guaranteed that that is
sufficient memory.
- The class containing user controls. These controls are described
in :ref:`control`. All controls that can be set using the
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` and
- :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` ioctl belong to this
+ :ref:`VIDIOC_G_CTRL` ioctl belong to this
class.
- .. row 2
:ref:`Video Overlay <overlay>` or :ref:`Video Output Overlay <osd>`
(OSD). The type of overlay is implied by the device type (capture or
output device) and can be determined with the
-:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` ioctl. One ``/dev/videoN``
+:ref:`VIDIOC_QUERYCAP` ioctl. One ``/dev/videoN``
device must not support both kinds of overlay.
The V4L2 API distinguishes destructive and non-destructive overlays. A
other parameters.
Information about video inputs is available using the
-:ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>` ioctl.
+:ref:`VIDIOC_ENUMINPUT` ioctl.
Return Value
negotiating any other parameters.
Information about video outputs is available using the
-:ref:`VIDIOC_ENUMOUTPUT <VIDIOC_ENUMOUTPUT>` ioctl.
+:ref:`VIDIOC_ENUMOUTPUT` ioctl.
Return Value
standard the driver returns an EINVAL error code. When the standard set
is ambiguous drivers may return EINVAL or choose any of the requested
standards. If the current input or output does not support standard
-video timings (e.g. if :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>`
+video timings (e.g. if :ref:`VIDIOC_ENUMINPUT`
does not set the ``V4L2_IN_CAP_STD`` flag), then ENODATA error code is
returned.
The selected audio mode, see :ref:`tuner-audmode` for valid
values. The audio mode does not affect audio subprogram detection,
- and like a :ref:`control <control>` it does not automatically
+ and like a :ref:`control` it does not automatically
change unless the requested mode is invalid or unsupported. See
:ref:`tuner-matrix` for possible results when the selected and
received audio programs do not match.
determined from the frequency band.) The set of supported video
standards is available from the struct
:ref:`v4l2_input <v4l2-input>` pointing to this tuner, see the
- description of ioctl :ref:`VIDIOC_ENUMINPUT <VIDIOC_ENUMINPUT>`
+ description of ioctl :ref:`VIDIOC_ENUMINPUT`
for details. Only ``V4L2_TUNER_ANALOG_TV`` tuners can have this
capability.
- 0x0400
- - The :ref:`VIDIOC_ENUM_FREQ_BANDS <VIDIOC_ENUM_FREQ_BANDS>`
+ - The :ref:`VIDIOC_ENUM_FREQ_BANDS`
ioctl can be used to enumerate the available frequency bands.
- .. row 13
- The range to search when using the hardware seek functionality is
programmable, see
- :ref:`VIDIOC_S_HW_FREQ_SEEK <VIDIOC_S_HW_FREQ_SEEK>` for
+ :ref:`VIDIOC_S_HW_FREQ_SEEK` for
details.
- .. row 14
takes a pointer to an integer which must be set to zero by the
application to stop overlay, to one to start.
-Drivers do not support :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` or
+Drivers do not support :ref:`VIDIOC_STREAMON` or
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` with
``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
and struct :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``type``.
Applications must also set the ``index`` field. Valid index numbers
range from zero to the number of buffers allocated with
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` (struct
+:ref:`VIDIOC_REQBUFS` (struct
:ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``count``) minus
one. The contents of the struct :c:type:`struct v4l2_buffer` returned
-by a :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl will do as well.
+by a :ref:`VIDIOC_QUERYBUF` ioctl will do as well.
When the buffer is intended for output (``type`` is
``V4L2_BUF_TYPE_VIDEO_OUTPUT``, ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``,
or ``V4L2_BUF_TYPE_VBI_OUTPUT``) applications must also initialize the
memory pages of the buffer in physical memory, they cannot be swapped
out to disk. Buffers remain locked until dequeued, until the
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl is called, or until the
+:ref:`VIDIOC_REQBUFS` ioctl is called, or until the
device is closed.
To enqueue a :ref:`DMABUF <dmabuf>` buffer applications set the
access (usually DMA). If an application accesses (reads/writes) a locked
buffer then the result is undefined. Buffers remain locked until
dequeued, until the :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl is called, or until the
+:ref:`VIDIOC_REQBUFS` ioctl is called, or until the
device is closed.
Applications call the ``VIDIOC_DQBUF`` ioctl to dequeue a filled
(e.g. because the pixelclock is out of range of the hardware
capabilities), then the driver fills in whatever timings it could find
and returns ERANGE. In that case the application can call
-:ref:`VIDIOC_DV_TIMINGS_CAP <VIDIOC_DV_TIMINGS_CAP>` to compare the
+:ref:`VIDIOC_DV_TIMINGS_CAP` to compare the
found timings with the hardware's capabilities in order to give more
precise feedback to the user.
This ioctl is part of the :ref:`streaming <mmap>` I/O method. It can
be used to query the status of a buffer at any time after buffers have
-been allocated with the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` ioctl.
+been allocated with the :ref:`VIDIOC_REQBUFS` ioctl.
Applications set the ``type`` field of a struct
:ref:`v4l2_buffer <v4l2-buffer>` to the same buffer type as was
and struct :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``type``,
and the ``index`` field. Valid index numbers range from zero to the
number of buffers allocated with
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` (struct
+:ref:`VIDIOC_REQBUFS` (struct
:ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``count``) minus
one. The ``reserved`` and ``reserved2`` fields must be set to 0. When
using the :ref:`multi-planar API <planar-apis>`, the ``m.planes``
- 0x00000400
- The device supports the
- :ref:`VIDIOC_S_HW_FREQ_SEEK <VIDIOC_S_HW_FREQ_SEEK>` ioctl
+ :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
for hardware frequency seeking.
- .. row 15
:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you need to
set the ``size`` field of struct
:ref:`v4l2_ext_control <v4l2-ext-control>` to 9. For
- :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you can set
+ :ref:`VIDIOC_G_EXT_CTRLS` you can set
the ``size`` field to ``maximum`` + 1. Which character encoding is
used will depend on the string control itself and should be part
of the control documentation.
:ref:`v4l2_tuner <v4l2-tuner>` ``capability`` field has the
``V4L2_TUNER_CAP_HWSEEK_PROG_LIM`` flag set, these values must fall
within one of the bands returned by
-:ref:`VIDIOC_ENUM_FREQ_BANDS <VIDIOC_ENUM_FREQ_BANDS>`. If the
+:ref:`VIDIOC_ENUM_FREQ_BANDS`. If the
``V4L2_TUNER_CAP_HWSEEK_PROG_LIM`` flag is not set, then these values
must exactly match those of one of the bands returned by
-:ref:`VIDIOC_ENUM_FREQ_BANDS <VIDIOC_ENUM_FREQ_BANDS>`. If the
+:ref:`VIDIOC_ENUM_FREQ_BANDS`. If the
current frequency of the tuner does not fall within the selected band it
will be clamped to fit in the band before the seek is started.
means all images captured but not dequeued yet will be lost, likewise
all images enqueued for output but not transmitted yet. I/O returns to
the same state as after calling
-:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` and can be restarted
+:ref:`VIDIOC_REQBUFS` and can be restarted
accordingly.
-If buffers have been queued with :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` and
+If buffers have been queued with :ref:`VIDIOC_QBUF` and
``VIDIOC_STREAMOFF`` is called without ever having called
``VIDIOC_STREAMON``, then those queued buffers will also be removed from
the incoming queue and all are returned to the same state as after
-calling :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` and can be restarted
+calling :ref:`VIDIOC_REQBUFS` and can be restarted
accordingly.
Both ioctls take a pointer to an integer, the desired buffer or stream
Available frame intervals may depend on the current 'try' formats at
other pads of the sub-device, as well as on the current active links.
-See :ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` for more
+See :ref:`VIDIOC_SUBDEV_G_FMT` for more
information about the try formats.
Sub-devices that support the frame interval enumeration ioctl should
This ioctl allows applications to enumerate all frame sizes supported by
a sub-device on the given pad for the given media bus format. Supported
formats can be retrieved with the
-:ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE <VIDIOC_SUBDEV_ENUM_MBUS_CODE>`
+:ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE`
ioctl.
To enumerate frame sizes applications initialize the ``pad``, ``which``
Available frame sizes may depend on the current 'try' formats at other
pads of the sub-device, as well as on the current active links and the
current values of V4L2 controls. See
-:ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` for more
+:ref:`VIDIOC_SUBDEV_G_FMT` for more
information about try formats.
Available media bus formats may depend on the current 'try' formats at
other pads of the sub-device, as well as on the current active links.
-See :ref:`VIDIOC_SUBDEV_G_FMT <VIDIOC_SUBDEV_G_FMT>` for more
+See :ref:`VIDIOC_SUBDEV_G_FMT` for more
information about the try formats.
**Note**
- This is an :ref:`obsolete <obsolete>` interface and may be removed
+ This is an :ref:`obsolete` interface and may be removed
in the future. It is superseded by
:ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`.
===========
Subscribe or unsubscribe V4L2 event. Subscribed events are dequeued by
-using the :ref:`VIDIOC_DQEVENT <VIDIOC_DQEVENT>` ioctl.
+using the :ref:`VIDIOC_DQEVENT` ioctl.
.. _v4l2-event-subscription:
projects / mirror_ubuntu-artful-kernel.git / commitdiff