[FFmpeg-devel] [PATCH v2 5/8] ffmpeg: use new decode API

[wm4]

On Thu, 24 Mar 2016 18:14:03 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Thu, Mar 24, 2016 at 06:03:49PM +0100, Michael Niedermayer wrote:
> > On Thu, Mar 24, 2016 at 03:34:58PM +0100, wm4 wrote:  
> > > On Wed, 23 Mar 2016 18:31:56 +0100
> > > Michael Niedermayer <michael at niedermayer.cc> wrote:
> > >   
> > > > On Wed, Mar 23, 2016 at 02:02:12PM +0100, wm4 wrote:  
> > > > > This is a bit messy, mainly due to timestamp handling.
> > > > > 
> > > > > decode_video() relied on the fact that it could set dts on a flush/drain
> > > > > packet. This is not possible with the old API, and won't be. (I think
> > > > > doing this was very questionable with the old API. Flush packets should
> > > > > not contain any information; they just cause a FIFO to be emptied.) This
> > > > > is replaced with checking the best_effort_timestamp for AV_NOPTS_VALUE,
> > > > > and using the suggested DTS in the drain case.
> > > > > 
> > > > > The fate-cavs test still fails due to dropping the last frame. This
> > > > > happens because the timestamp of the last frame goes backwards
> > > > > (ffprobe -show_frames shows the same thing). I suspect that this
> > > > > "worked" due to the best effort timestamp logic picking the DTS
> > > > > over the decreasing PTS. Since this logic is in libavcodec (where
> > > > > it probably shouldn't be), this can't be easily fixed. The timestamps
> > > > > of the cavs samples are weird anyway, so I chose not to fix it.
> > > > > 
> > > > > Another strange thing is the timestamp handling in the video path of
> > > > > process_input_packet (after the decode_video() call). It looks like
> > > > > the code to increase next_dts and next_pts should be run every time
> > > > > a frame is decoded - but it's needed even if output is skipped.
> > > > > ---
> > > > >  ffmpeg.c            | 126 +++++++++++++++++++++++++++++++---------------------
> > > > >  tests/ref/fate/cavs |   1 -
> > > > >  2 files changed, 75 insertions(+), 52 deletions(-)    
> > > > 
> > > > this does not pass fate
> > > > make -j12 fate -k THREAD_TYPE=frame THREADS=5
> > > > passes before this commit but fails afterwards
> > > > 
> > > > make: *** [fate-filter-hq2x] Error 1
> > > > make: *** [fate-filter-3xbr] Error 1
> > > > make: *** [fate-filter-hq4x] Error 1
> > > > make: *** [fate-filter-4xbr] Error 1
> > > > make: *** [fate-filter-2xbr] Error 1
> > > > make: *** [fate-filter-hq3x] Error 1
> > > > make: *** [fate-h264-reinit-large_420_8-to-small_420_8] Error 1
> > > > make: *** [fate-h264-reinit-small_420_9-to-small_420_8] Error 1
> > > > make: *** [fate-h264-reinit-small_420_8-to-large_444_10] Error 1
> > > > make: *** [fate-h264-reinit-small_422_9-to-small_420_9] Error 1
> > > > make: *** [fate-hevc-paramchange-yuv420p-yuv420p10] Error 1
> > > > 
> > > > [...]  
> > > 
> > > It's the timestamp insanity again. Patch: http://sprunge.us/AYgA
> > > 
> > > The hqx/xbr checks fail because somehow it doesn't make sure it
> > > drains the filter graph on parameter changes. The frames sent to the
> > > filter graph are exactly the same before and after my change. I don't
> > > know why it gets the the output frame soon enough out the graph before
> > > my patches. The solution is not running these tests with threading
> > > enabled, or to fix filter draining on parameter changes. At least it
> > > looks to me like it's broken in the general case and before my patches,
> > > and it worked by luck.  
> > 
> > it seems with this patch (with and withut the update above) sometimes
> > more frames are passed through the filter chain than before
> > 
> > is that intended ?
> > 
> > example: (see the number of lines generated from cropdetect)
> > ./ffmpeg -i ~/tickets/3030/cropdetect.mp4 -vframes 15 -an  -vf "cropdetect" -f null -
> > 
> > the actual number of frames written to the output does not change
> > though  
> 
> also libutvideo aborts with this patch
> example:
> ./ffmpeg -vcodec libutvideo -i utvideo-yuv422p10le_UQY2_crc32-A431CD5F.avi -f null -
> 
> Assertion avctx->internal->buffer_frame->buf[0] failed at libavcodec/utils.c:2753
> Aborted
> 
> video should be here: http://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket4044/
> 
> The file does not decode with our utvideo decoder
> 
> should i investigate this ? (asking as libutvideo was said to be hard
> to build)
> 

This just means the decoder doesn't return refcounted frames, like
libavcodec guarantees if refcounted_frames is set. The decoder wrapper
is buggy.