A queued request cannot be modified anymore.
.. caution::
- For :ref:`memory-to-memory devices <codec>` you can use requests only for
+ For :ref:`memory-to-memory devices <mem2mem>` you can use requests only for
output buffers, not for capture buffers. Attempting to add a capture buffer
to a request will result in an ``EACCES`` error.
Example for a Codec Device
--------------------------
-For use-cases such as :ref:`codecs <codec>`, the request API can be used
+For use-cases such as :ref:`codecs <mem2mem>`, the request API can be used
to associate specific controls to
be applied by the driver for the OUTPUT buffer, allowing user-space
to queue many such buffers in advance. It can also take advantage of requests'
+++ /dev/null
-.. Permission is granted to copy, distribute and/or modify this
-.. document under the terms of the GNU Free Documentation License,
-.. Version 1.1 or any later version published by the Free Software
-.. Foundation, with no Invariant Sections, no Front-Cover Texts
-.. and no Back-Cover Texts. A copy of the license is included at
-.. Documentation/media/uapi/fdl-appendix.rst.
-..
-.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
-
-.. _codec:
-
-***************
-Codec Interface
-***************
-
-A V4L2 codec can compress, decompress, transform, or otherwise convert
-video data from one format into another format, in memory. Typically
-such devices are memory-to-memory devices (i.e. devices with the
-``V4L2_CAP_VIDEO_M2M`` or ``V4L2_CAP_VIDEO_M2M_MPLANE`` capability set).
-
-A memory-to-memory video node acts just like a normal video node, but it
-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>`
-for both capture and output to start the codec.
-
-Video compression codecs use the MPEG controls to setup their codec
-parameters
-
-.. note::
-
- The MPEG controls actually support many more codecs than
- just MPEG. See :ref:`mpeg-controls`.
-
-Memory-to-memory devices function as a shared resource: you can
-open the video node multiple times, each application setting up their
-own codec properties that are local to the file handle, and each can use
-it independently from the others. The driver will arbitrate access to
-the codec and reprogram it whenever another file handler gets access.
-This is different from the usual video node behavior where the video
-properties are global to the device (i.e. changing something through one
-file handle is visible through another file handle).
--- /dev/null
+.. Permission is granted to copy, distribute and/or modify this
+.. document under the terms of the GNU Free Documentation License,
+.. Version 1.1 or any later version published by the Free Software
+.. Foundation, with no Invariant Sections, no Front-Cover Texts
+.. and no Back-Cover Texts. A copy of the license is included at
+.. Documentation/media/uapi/fdl-appendix.rst.
+..
+.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _mem2mem:
+
+********************************
+Video Memory-To-Memory Interface
+********************************
+
+A V4L2 memory-to-memory device can compress, decompress, transform, or
+otherwise convert video data from one format into another format, in memory.
+Such memory-to-memory devices set the ``V4L2_CAP_VIDEO_M2M`` or
+``V4L2_CAP_VIDEO_M2M_MPLANE`` capability. Examples of memory-to-memory
+devices are codecs, scalers, deinterlacers or format converters (i.e.
+converting from YUV to RGB).
+
+A memory-to-memory video node acts just like a normal video node, but it
+supports both output (sending frames from memory to the hardware)
+and capture (receiving the processed frames from the 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>`
+for both capture and output to start the hardware.
+
+Memory-to-memory devices function as a shared resource: you can
+open the video node multiple times, each application setting up their
+own properties that are local to the file handle, and each can use
+it independently from the others. The driver will arbitrate access to
+the hardware and reprogram it whenever another file handler gets access.
+This is different from the usual video node behavior where the video
+properties are global to the device (i.e. changing something through one
+file handle is visible through another file handle).
+
+One of the most common memory-to-memory device is the codec. Codecs
+are more complicated than most and require additional setup for
+their codec parameters. This is done through codec controls.
+See :ref:`mpeg-controls`.
dev-overlay
dev-output
dev-osd
- dev-codec
+ dev-mem2mem
dev-raw-vbi
dev-sliced-vbi
dev-radio
- 'MG2S'
- MPEG-2 parsed slice data, as extracted from the MPEG-2 bitstream.
This format is adapted for stateless video decoders that implement a
- MPEG-2 pipeline (using the :ref:`codec` and :ref:`media-request-api`).
+ MPEG-2 pipeline (using the :ref:`mem2mem` and :ref:`media-request-api`).
Metadata associated with the frame to decode is required to be passed
through the ``V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS`` control and
quantization matrices can optionally be specified through the
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or calling :ref:`VIDIOC_REQBUFS`
the check for this will be reset.
- For :ref:`memory-to-memory devices <codec>` you can specify the
+ For :ref:`memory-to-memory devices <mem2mem>` you can specify the
``request_fd`` only for output buffers, not for capture buffers. Attempting
to specify this for a capture buffer will result in an ``EACCES`` error.
projects / platform / kernel / linux-starfive.git / commitdiff