VAAPI encoding on Coffee Lake skipping/missing frames

[Dan Seeker]

Summary of the bug:

Using h264_vaapi encoder on an Ubuntu 16.04 with Intel i9-8700 on .mov input outputs video stream with only keyframes. The result is a video with still frames changing every 3-5 seconds.

The same encoder (h264_vaapi) works normally on other h264 input.
Using -intra with h264_vaapi outputs all frames correctly.
Switching from h264_vaapi to hevc_vaapi encodes properly with all frames.

ffmpeg version 4.02 built on docker container (vaapi) from ​https://hub.docker.com/r/jrottenberg/ffmpeg/
problem also occurs on the 3.x container

How to reproduce:

% ffmpeg -stats -report -vaapi_device /dev/dri/renderD128 -hwaccel_output_format vaapi -hwaccel vaapi -t 30 -i input.mov -an -filter_complex "format=nv12|vaapi,hwupload" -c:v h264_vaapi -qp 28 -bf 0 -compression_level 0 -quality 0 output.mp4 -y

[Dan Seeker]

report of file

[Dan Seeker]

report h264_vaapi intra

[Dan Seeker]

report hevc_vaapi

[Dan Seeker]

h264_vaapi output skipping frames

[Dan Seeker]

PS: I tried connecting to the FTP to upload the source but it's timing out
here's a google drive link to the source
​https://drive.google.com/open?id=1PpB7J4rjoDhi82dy6K9BR1JBbbdB6vfD

[Carl Eugen Hoyos]

Please test current FFmpeg git head and provide the log file, no other version is supported here.

[jkqxz]

Can you try with <​https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2018-October/235692.html> applied?

The only problem I can see here is that the SAR gets written incorrectly because it doesn't fit in the 2¹⁶ range. I'm not sure how that causes the observed issue, but fixing it seems to help.

That is, if I fix the SAR in your file with:

ffmpeg -i vaapi_skipping-frames_h264.mp4 -c:v copy -bsf:v h264_metadata=sample_aspect_ratio=1 output.mp4

then the output file plays correctly where the input did not.

[Dan Seeker]

@jkqxz yes changing the sample_aspect_ratio did correct all the frame encoding, even thou the aspect ratio got distorted. I'll try to get the value somewhere else and enforce it.

I noted this message when trying to re-encode the file for testing, may have something to do with it?

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5598d1728000] sample aspect ratio already set to 93207:65536, ignoring 'pasp' atom (118:81)

I will try to update the build, but since I'm using the hosted docker container I haven't a clue how to update the branch there.

[Dan Seeker]

This fraction problem seems to extend beyond the vaapi encoder. The same content outputs incorrectly with image extraction (png or jpg). it's necessary to manually add scaling with the appropriate AR to adjust, otherwise the output scaling is incorrect.

I couldn't test the new branches, but was able to fix all the problems with manually overriding the AR truncating to 6 digits

[Carl Eugen Hoyos]

Fixed in a830056b32feb2db463e062d4ec2b6fb47ec70ee