Re: [PATCH v2 0/6] media: cedrus: h264: Support multi-slice frames

Jernej Škrabec
2019-09-30T22:27:42Z

Dne ponedeljek, 30. september 2019 ob 10:10:48 CEST je Hans Verkuil
napisal(a):
> On 9/29/19 10:00 PM, Jernej Skrabec wrote:
> > This series adds support for decoding multi-slice H264 frames along with
> > support for V4L2_DEC_CMD_FLUSH and V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF.
> >
> > Code was tested by modified ffmpeg, which can be found here:
> > https://github.com/jernejsk/FFmpeg, branch mainline-test
> > It has to be configured with at least following options:
> > --enable-v4l2-request --enable-libudev --enable-libdrm
> >
> > Samples used for testing:
> > http://jernej.libreelec.tv/videos/h264/BA1_FT_C.mp4
> > http://jernej.libreelec.tv/videos/h264/h264.mp4
> >
> > Command line used for testing:
> > ffmpeg -hwaccel drm -hwaccel_device /dev/dri/card0 -i h264.mp4 -pix_fmt
> > bgra -f fbdev /dev/fb0
> >
> > Please note that V4L2_DEC_CMD_FLUSH was not tested because I'm
> > not sure how. ffmpeg follows exactly which slice is last in frame
> > and sets hold flag accordingly. Improper usage of hold flag would
> > corrupt ffmpeg assumptions and it would probably crash. Any ideas
> > how to test this are welcome!
>
> It can be tested partially at least: if ffmpeg tells you it is the last
> slice, then queue the slice with the HOLD flag set, then call FLUSH
> afterwards. This should clear the HOLD flag again. In this case the queued
> buffer is probably not yet processed, so the flag is cleared before the
> decode job starts.
>
> You can also try to add a sleep before calling FLUSH to see what happens
> if the last queued buffer is already decoded.

Ok, I tried following code:
https://github.com/jernejsk/FFmpeg/blob/flush_test/libavcodec/
v4l2_request.c#L220-L233

But results are not good. It seems that out_vb in flush command is always NULL
and so it always marks capture buffer as done, which leads to kernel warnings.

dmesg output with debugging messages is here: http://ix.io/1Ks8

Currently I'm not sure what is going on. Shouldn't be output buffer queued and
waiting to MEDIA_REQUEST_IOC_QUEUE which is executed after flush command as it
can be seen from ffmpeg code linked above?

Best regards,
Jernej

>
> Regards,
>
> Hans
>
> > Thanks to Jonas for adjusting ffmpeg.
> >
> > Please let me know what you think.
> >
> > Best regards,
> > Jernej
> >
> > Changes from v1:
> > - added Rb tags
> > - updated V4L2_DEC_CMD_FLUSH documentation
> > - updated first slice detection in Cedrus
> > - hold capture buffer flag is set according to source format
> > - added v4l m2m stateless_(try_)decoder_cmd ioctl helpers
> >
> > Hans Verkuil (2):
> > vb2: add V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF
> > videodev2.h: add V4L2_DEC_CMD_FLUSH
> >
> > Jernej Skrabec (4):
> > media: v4l2-mem2mem: add stateless_(try_)decoder_cmd ioctl helpers
> > media: cedrus: Detect first slice of a frame
> > media: cedrus: h264: Support multiple slices per frame
> > media: cedrus: Add support for holding capture buffer
> >
> > Documentation/media/uapi/v4l/buffer.rst | 13 ++++++
> > .../media/uapi/v4l/vidioc-decoder-cmd.rst | 10 +++-
> > .../media/uapi/v4l/vidioc-reqbufs.rst | 6 +++
> > .../media/videodev2.h.rst.exceptions | 1 +
> > .../media/common/videobuf2/videobuf2-v4l2.c | 8 +++-
> > drivers/media/v4l2-core/v4l2-mem2mem.c | 35 ++++++++++++++
> > drivers/staging/media/sunxi/cedrus/cedrus.h | 1 +
> > .../staging/media/sunxi/cedrus/cedrus_dec.c | 11 +++++
> > .../staging/media/sunxi/cedrus/cedrus_h264.c | 11 ++++-
> > .../staging/media/sunxi/cedrus/cedrus_hw.c | 8 ++--
> > .../staging/media/sunxi/cedrus/cedrus_video.c | 14 ++++++
> > include/media/v4l2-mem2mem.h | 46 +++++++++++++++++++
> > include/media/videobuf2-core.h | 3 ++
> > include/media/videobuf2-v4l2.h | 5 ++
> > include/uapi/linux/videodev2.h | 14 ++++--
> > 15 files changed, 175 insertions(+), 11 deletions(-)