Re: [PATCH 00/14] Stateful/stateless codec core support (resend)

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On Wed, Jul 24, 2019 at 1:27 PM Hans Verkuil <hverkuil-cisco@xxxxxxxxx> wrote:
>
> (There were too many recipients for my provider, so resending
> again without the zillion CCs, and in batches of 5 patches. Stupid
> spammer detection...)
>
> This series consolidates various patches/patch series that add
> features or document memory-to-memory video codec interfaces.
>
> This includes patches adding V4L2_FMT_FLAG_DYN_RESOLUTION,
> new code adding V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER, new code
> adding V4L2_DEC_CMD_FLUSH, patches adding V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF
> (now with documentation) and patches documenting the stateful
> encoder/decoder and stateless decoder.
>
> The stateful encoder documentation is still RFC quality (there are
> open TODOs, see https://patchwork.kernel.org/cover/10972783/).
>
> The stateless decoder documentation is the same as the v5 posted
> by Alexandre, but with my comments incorporated.
>
> Also added are updated pixelformat descriptions. Please review this!
> I didn't update the MPEG4 format since I'm not sure what to put there.
>
> If anyone has access to recent codec standards, then I would really
> like to have the right references to 'MPEG Picture' and 'Access Unit'.
> It would be good to just refer to the definition of what a Picture
> or Access Unit is in the right standards.
>
> Changes for the stateful decoder documentation since v4:
>
> - In the Decoding section change "multiple ``OUTPUT`` buffers generate
>   one ``CAPTURE`` buffer: timestamp of the ``OUTPUT`` buffer queued last
>   will be copied." to "queued first" since this corresponds to
>   existing implementations.
>
> - Document that width and height are required fields in step 4 of the
>   Capture Setup.
>
> - Mention the new ENUM_FMT flags.
>
> Changes for the stateless decoder documentation since v5:
>
> - Document that width and height are required fields in step 4 of the
>   Capture Setup.
>
> - Mention the new V4L2_DEC_CMD_FLUSH command to flush the last held
>   capture buffer. This replaces the 'queue an empty buffer' solution.
>
> In my view this series is ready to go in, except for the last patch
> (stateful encoder).
>
> Maxime, I didn't add the proposed V4L2_FMT_FLAG_MANUAL_RESOLUTION
> flag since I think that can go in separately. I also am not 100%
> happy with that name, although I can't think of a better one.
>

Sure! I can prepare an RFC once this series lands if you wish.

> Regards,
>
>         Hans
>
> Alexandre Courbot (1):
>   media: docs-rst: Document m2m stateless video decoder interface
>
> Hans Verkuil (6):
>   v4l2-ioctl.c: OR flags in v4l_fill_fmtdesc(), not don't overwrite
>   videodev2.h: add V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER
>   videodev2.h.rst.exceptions: tymecode -> timecode
>   vb2: add V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF
>   videodev2.h: add V4L2_DEC_CMD_FLUSH
>   pixfmt-compressed.rst: improve H264/HEVC/MPEG1+2/VP8+9 documentation
>
> Maxime Jourdan (5):
>   videodev2.h: add V4L2_FMT_FLAG_DYN_RESOLUTION
>   media: venus: vdec: flag OUTPUT formats with
>     V4L2_FMT_FLAG_DYN_RESOLUTION
>   media: s5p_mfc_dec: set flags for OUTPUT coded formats
>   media: mtk-vcodec: flag OUTPUT formats with
>     V4L2_FMT_FLAG_DYN_RESOLUTION
>   media: vicodec: set flags for vdec/stateful OUTPUT coded formats
>
> Tomasz Figa (2):
>   media: docs-rst: Document memory-to-memory video decoder interface
>   media: docs-rst: Document memory-to-memory video encoder interface
>
>  Documentation/media/uapi/v4l/buffer.rst       |   13 +
>  Documentation/media/uapi/v4l/dev-decoder.rst  | 1101 +++++++++++++++++
>  Documentation/media/uapi/v4l/dev-encoder.rst  |  608 +++++++++
>  Documentation/media/uapi/v4l/dev-mem2mem.rst  |   10 +-
>  .../media/uapi/v4l/dev-stateless-decoder.rst  |  424 +++++++
>  .../media/uapi/v4l/pixfmt-compressed.rst      |   36 +-
>  Documentation/media/uapi/v4l/pixfmt-v4l2.rst  |   10 +
>  Documentation/media/uapi/v4l/v4l2.rst         |   12 +-
>  .../media/uapi/v4l/vidioc-decoder-cmd.rst     |   52 +-
>  .../media/uapi/v4l/vidioc-dqevent.rst         |   11 +-
>  .../media/uapi/v4l/vidioc-encoder-cmd.rst     |   51 +-
>  .../media/uapi/v4l/vidioc-enum-fmt.rst        |   16 +
>  .../media/uapi/v4l/vidioc-reqbufs.rst         |    6 +
>  .../media/videodev2.h.rst.exceptions          |    7 +-
>  .../media/common/videobuf2/videobuf2-v4l2.c   |    8 +-
>  .../platform/mtk-vcodec/mtk_vcodec_dec.c      |    4 +
>  .../platform/mtk-vcodec/mtk_vcodec_drv.h      |    1 +
>  drivers/media/platform/qcom/venus/core.h      |    1 +
>  drivers/media/platform/qcom/venus/vdec.c      |   11 +
>  .../media/platform/s5p-mfc/s5p_mfc_common.h   |    1 +
>  drivers/media/platform/s5p-mfc/s5p_mfc_dec.c  |   18 +
>  drivers/media/platform/vicodec/vicodec-core.c |    3 +
>  drivers/media/v4l2-core/v4l2-ioctl.c          |    2 +-
>  include/media/v4l2-mem2mem.h                  |   42 +
>  include/media/videobuf2-core.h                |    3 +
>  include/media/videobuf2-v4l2.h                |    5 +
>  include/uapi/linux/videodev2.h                |   20 +-
>  27 files changed, 2419 insertions(+), 57 deletions(-)
>  create mode 100644 Documentation/media/uapi/v4l/dev-decoder.rst
>  create mode 100644 Documentation/media/uapi/v4l/dev-encoder.rst
>  create mode 100644 Documentation/media/uapi/v4l/dev-stateless-decoder.rst
>
> --
> 2.20.1
>

Thank you for including my series with your modifications on top.

The patches regarding stateful decoders are fine by me. To nitpick, I
would maybe rename V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER to something
such as:
 - V4L2_FMT_FLAG_FLEXIBLE_BITSTREAM_PARSER
 - V4L2_FMT_FLAG_PERMISSIVE_BITSTREAM_PARSER

Since by definition a stateful decoder is able to parse the bitstream,
it could be a bit confusing to see a format without
V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER, something actually quite common.
But it is all well explained in the format documentation (patch 11/14)
and is of low-ish importance, so I don't really mind either.

Maxime



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