On 8/14/19 3:09 PM, Paul Kocialkowski wrote:
> 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.
Hmm, how about:
If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM``
then the decoder can start streaming at any point in the bytestream and
it can parse the Access Units by itself.
What do you think?
Hans
>
> 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
>>
>
