| Message ID | 4792b823-6eb1-536b-08d6-5cad28bb2f24@xs4all.nl (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
Hi Hans, On Wed, Jan 23, 2019 at 5:07 PM Hans Verkuil <hverkuil-cisco@xs4all.nl> wrote: > > The "Codec Interface" chapter is poorly named since codecs are just one > use-case of the Memory-to-Memory Interface. Rename it and clean up the > text a bit. > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> > --- > Incorporated Tomasz' comments. > > Note that I moved the section about codec controls to the end. The idea > is that when we add the codec specs this section is updated and the > links to those specs is added there. > --- > .../media/uapi/mediactl/request-api.rst | 4 +- > .../v4l/{dev-codec.rst => dev-mem2mem.rst} | 41 +++++++++---------- > Documentation/media/uapi/v4l/devices.rst | 2 +- > .../media/uapi/v4l/pixfmt-compressed.rst | 2 +- > Documentation/media/uapi/v4l/vidioc-qbuf.rst | 2 +- > 5 files changed, 25 insertions(+), 26 deletions(-) > rename Documentation/media/uapi/v4l/{dev-codec.rst => dev-mem2mem.rst} (50%) > Thanks a lot! Reviewed-by: Tomasz Figa <tfiga@chromium.org> Best regards, Tomasz
On Wed, Jan 23, 2019 at 5:07 PM Hans Verkuil <hverkuil-cisco@xs4all.nl> wrote: > > The "Codec Interface" chapter is poorly named since codecs are just one > use-case of the Memory-to-Memory Interface. Rename it and clean up the > text a bit. > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> > --- > Incorporated Tomasz' comments. > > Note that I moved the section about codec controls to the end. The idea > is that when we add the codec specs this section is updated and the > links to those specs is added there. Makes sense indeed! Acked-by: Alexandre Courbot <acourbot@chromium.org> > --- > .../media/uapi/mediactl/request-api.rst | 4 +- > .../v4l/{dev-codec.rst => dev-mem2mem.rst} | 41 +++++++++---------- > Documentation/media/uapi/v4l/devices.rst | 2 +- > .../media/uapi/v4l/pixfmt-compressed.rst | 2 +- > Documentation/media/uapi/v4l/vidioc-qbuf.rst | 2 +- > 5 files changed, 25 insertions(+), 26 deletions(-) > rename Documentation/media/uapi/v4l/{dev-codec.rst => dev-mem2mem.rst} (50%) > > diff --git a/Documentation/media/uapi/mediactl/request-api.rst b/Documentation/media/uapi/mediactl/request-api.rst > index 4b25ad03f45a..1ad631e549fe 100644 > --- a/Documentation/media/uapi/mediactl/request-api.rst > +++ b/Documentation/media/uapi/mediactl/request-api.rst > @@ -91,7 +91,7 @@ A request must contain at least one buffer, otherwise ``ENOENT`` is returned. > 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. > > @@ -152,7 +152,7 @@ if it had just been allocated. > 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' > diff --git a/Documentation/media/uapi/v4l/dev-codec.rst b/Documentation/media/uapi/v4l/dev-mem2mem.rst > similarity index 50% > rename from Documentation/media/uapi/v4l/dev-codec.rst > rename to Documentation/media/uapi/v4l/dev-mem2mem.rst > index b5e017c17834..67a980818dc8 100644 > --- a/Documentation/media/uapi/v4l/dev-codec.rst > +++ b/Documentation/media/uapi/v4l/dev-mem2mem.rst > @@ -7,37 +7,36 @@ > .. > .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > > -.. _codec: > +.. _mem2mem: > > -*************** > -Codec Interface > -*************** > +******************************** > +Video Memory-To-Memory 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 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 codec hardware) > -and capture (receiving the processed frames from the codec hardware into > +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 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`. > +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 codec properties that are local to the file handle, and each can use > +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 codec and reprogram it whenever another file handler gets access. > +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`. > diff --git a/Documentation/media/uapi/v4l/devices.rst b/Documentation/media/uapi/v4l/devices.rst > index d6fcf3db5909..07f8d047662b 100644 > --- a/Documentation/media/uapi/v4l/devices.rst > +++ b/Documentation/media/uapi/v4l/devices.rst > @@ -21,7 +21,7 @@ Interfaces > dev-overlay > dev-output > dev-osd > - dev-codec > + dev-mem2mem > dev-raw-vbi > dev-sliced-vbi > dev-radio > diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst > index e4c5e456df59..2675bef3eefe 100644 > --- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst > +++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst > @@ -73,7 +73,7 @@ Compressed Formats > - '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 > diff --git a/Documentation/media/uapi/v4l/vidioc-qbuf.rst b/Documentation/media/uapi/v4l/vidioc-qbuf.rst > index 3259168a7358..c138d149faea 100644 > --- a/Documentation/media/uapi/v4l/vidioc-qbuf.rst > +++ b/Documentation/media/uapi/v4l/vidioc-qbuf.rst > @@ -123,7 +123,7 @@ then ``EINVAL`` will be returned. > :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. > > -- > 2.20.1 > >
diff --git a/Documentation/media/uapi/mediactl/request-api.rst b/Documentation/media/uapi/mediactl/request-api.rst index 4b25ad03f45a..1ad631e549fe 100644 --- a/Documentation/media/uapi/mediactl/request-api.rst +++ b/Documentation/media/uapi/mediactl/request-api.rst @@ -91,7 +91,7 @@ A request must contain at least one buffer, otherwise ``ENOENT`` is returned. 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. @@ -152,7 +152,7 @@ if it had just been allocated. 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' diff --git a/Documentation/media/uapi/v4l/dev-codec.rst b/Documentation/media/uapi/v4l/dev-mem2mem.rst similarity index 50% rename from Documentation/media/uapi/v4l/dev-codec.rst rename to Documentation/media/uapi/v4l/dev-mem2mem.rst index b5e017c17834..67a980818dc8 100644 --- a/Documentation/media/uapi/v4l/dev-codec.rst +++ b/Documentation/media/uapi/v4l/dev-mem2mem.rst @@ -7,37 +7,36 @@ .. .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections -.. _codec: +.. _mem2mem: -*************** -Codec Interface -*************** +******************************** +Video Memory-To-Memory 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 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 codec hardware) -and capture (receiving the processed frames from the codec hardware into +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 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`. +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 codec properties that are local to the file handle, and each can use +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 codec and reprogram it whenever another file handler gets access. +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`. diff --git a/Documentation/media/uapi/v4l/devices.rst b/Documentation/media/uapi/v4l/devices.rst index d6fcf3db5909..07f8d047662b 100644 --- a/Documentation/media/uapi/v4l/devices.rst +++ b/Documentation/media/uapi/v4l/devices.rst @@ -21,7 +21,7 @@ Interfaces dev-overlay dev-output dev-osd - dev-codec + dev-mem2mem dev-raw-vbi dev-sliced-vbi dev-radio diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst index e4c5e456df59..2675bef3eefe 100644 --- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst +++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst @@ -73,7 +73,7 @@ Compressed Formats - '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 diff --git a/Documentation/media/uapi/v4l/vidioc-qbuf.rst b/Documentation/media/uapi/v4l/vidioc-qbuf.rst index 3259168a7358..c138d149faea 100644 --- a/Documentation/media/uapi/v4l/vidioc-qbuf.rst +++ b/Documentation/media/uapi/v4l/vidioc-qbuf.rst @@ -123,7 +123,7 @@ then ``EINVAL`` will be returned. :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.
The "Codec Interface" chapter is poorly named since codecs are just one use-case of the Memory-to-Memory Interface. Rename it and clean up the text a bit. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> --- Incorporated Tomasz' comments. Note that I moved the section about codec controls to the end. The idea is that when we add the codec specs this section is updated and the links to those specs is added there. --- .../media/uapi/mediactl/request-api.rst | 4 +- .../v4l/{dev-codec.rst => dev-mem2mem.rst} | 41 +++++++++---------- Documentation/media/uapi/v4l/devices.rst | 2 +- .../media/uapi/v4l/pixfmt-compressed.rst | 2 +- Documentation/media/uapi/v4l/vidioc-qbuf.rst | 2 +- 5 files changed, 25 insertions(+), 26 deletions(-) rename Documentation/media/uapi/v4l/{dev-codec.rst => dev-mem2mem.rst} (50%)