Hi,
On Mon 12 Aug 19, 13:05, Hans Verkuil wrote:
> The existing documentation was incorrect and did not correspond
> to how actual codec drivers implemented this.
>
> Update the documentation to explicitly specify what is actually
> expected.
>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
> .../media/uapi/v4l/pixfmt-compressed.rst | 36 +++++++++++++++----
> 1 file changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> index f52a7b67023d..9bb4a172a660 100644
> --- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> +++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> @@ -41,7 +41,12 @@ Compressed Formats
>
> - ``V4L2_PIX_FMT_H264``
> - 'H264'
> - - H264 video elementary stream with start codes.
> + - H264 Access Unit.
> + The decoder expects one Access Unit per buffer.
> + The encoder generates one Access Unit per buffer.
> + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
> + then the decoder has no requirements since it can parse all the
> + information from the raw bytestream.
Maybe it would be clearer to mention that "no requirements" concerns the
lack of frame/field boundary requirement? Otherwise it feels a bit unclear
what userspace is expected to do or not do depending on the flag.
Cheers,
Paul
> * .. _V4L2-PIX-FMT-H264-NO-SC:
>
> - ``V4L2_PIX_FMT_H264_NO_SC``
> @@ -86,12 +91,20 @@ Compressed Formats
>
> - ``V4L2_PIX_FMT_MPEG1``
> - 'MPG1'
> - - MPEG1 video elementary stream.
> + - MPEG1 Picture. Each buffer starts with a Picture header, followed
> + by other headers as needed and ending with the Picture data.
> + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
> + then the decoder has no requirements since it can parse all the
> + information from the raw bytestream.
> * .. _V4L2-PIX-FMT-MPEG2:
>
> - ``V4L2_PIX_FMT_MPEG2``
> - 'MPG2'
> - - MPEG2 video elementary stream.
> + - MPEG2 Picture. Each buffer starts with a Picture header, followed
> + by other headers as needed and ending with the Picture data.
> + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
> + then the decoder has no requirements since it can parse all the
> + information from the raw bytestream.
> * .. _V4L2-PIX-FMT-MPEG2-SLICE:
>
> - ``V4L2_PIX_FMT_MPEG2_SLICE``
> @@ -132,7 +145,9 @@ Compressed Formats
>
> - ``V4L2_PIX_FMT_VP8``
> - 'VP80'
> - - VP8 video elementary stream.
> + - VP8 compressed video frame. The encoder generates one
> + compressed frame per buffer, and the decoder requires one
> + compressed frame per buffer.
> * .. _V4L2-PIX-FMT-VP8-FRAME:
>
> - ``V4L2_PIX_FMT_VP8_FRAME``
> @@ -157,12 +172,19 @@ Compressed Formats
>
> - ``V4L2_PIX_FMT_VP9``
> - 'VP90'
> - - VP9 video elementary stream.
> + - VP9 compressed video frame. The encoder generates one
> + compressed frame per buffer, and the decoder requires one
> + compressed frame per buffer.
> * .. _V4L2-PIX-FMT-HEVC:
>
> - ``V4L2_PIX_FMT_HEVC``
> - 'HEVC'
> - - HEVC/H.265 video elementary stream.
> + - HEVC/H.265 Access Unit.
> + The decoder expects one Access Unit per buffer.
> + The encoder generates one Access Unit per buffer.
> + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
> + then the decoder has no requirements since it can parse all the
> + information from the raw bytestream.
> * .. _V4L2-PIX-FMT-FWHT:
>
> - ``V4L2_PIX_FMT_FWHT``
> @@ -170,6 +192,8 @@ Compressed Formats
> - Video elementary stream using a codec based on the Fast Walsh Hadamard
> Transform. This codec is implemented by the vicodec ('Virtual Codec')
> driver. See the codec-fwht.h header for more details.
> + :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
> + since the decoder can parse all the information from the raw bytestream.
> * .. _V4L2-PIX-FMT-FWHT-STATELESS:
>
> - ``V4L2_PIX_FMT_FWHT_STATELESS``
> --
> 2.20.1
>
--
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
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