Av1an output skips sections, has still frame at the end of the Video and desynced audio

[OParczyk]

Hi! I've deinterlaced some partially interlaced DVD footage using ffmpeg -i video.mkv -map_metadata 0 -map 0 -c:v ffv1 -vf "fieldmatch=order=tff:combmatch=full, bwdif=deint=interlaced" video_deint.mkv To only deinterlace the parts of the video that actually need it. The resulting video File is in this way properly deinterlaced and plays fine.

I then try to use av1an to convert it to av1 (using rav1e) and x265 to compare the results: av1an --temp /media/user/ramdisk/av1antmp -i video_deint.mkv -w 6 --chunk-method hybrid -e rav1e --target-quality 93 --vmaf -o video_av1_deint.mkv and av1an --temp /media/user/ramdisk/av1antmp -i video_deint.mkv -w 6 --chunk-method hybrid -e x265 -c mkvmerge --target-quality 93 --vmaf -o video_deint_265.mkv

Av1an completes without warning nor error in both cases. The resulting video file though has a lot of missing sections and the sound desyncs because of it. This is visualized in the attached vmaf svg graphs:

This also happens to other video files I've treated this way.

I'd be happy to send you a link to the video.mkv and video_deint.mkv in question via mail on request (it's just the studios intros), but I'm weary of sharing it here publicly for copyright reasons.

I'm using a 3 day old build of rav1e and ffmpeg, av1an is current from cargo, all else is current ubuntu 22.04

[master-of-zen]

Can you provide 1 minute (for test) example of source? Have you tried to deinterlace into AVC(x264)?

[OParczyk]

I've sent you an email to your commit email address with a link to two example source files: 1min.mkv was extracted using ffmpeg -fflags +genpts -ss 00:06:30 -to 00:07:30 -i A1_t01.mkv -c copy -map 0 -map_metadata 0 1min.mkv and A1_t00.mkv is directly remuxed dvd video. Both exhibit the issue at hand. The presence of -fflags +genpts makes no difference in behavior, but I've left it in here. 1min.mkv causes av1an to crash when given as input directly: av1an --temp /media/user/ramdisk/av1antmp -i 1min.mkv -w 6 --chunk-method hybrid -e x265 -c mkvmerge --target-quality 93 --vmaf -o 1min_265.mkv but that's probably another issue. I've included A1_00.mkv because it doesn't doesn't cause this crash, yet many other of my to be converted videos do with the same error.

I've tried deinterlacing into x264: ffmpeg -i 1min.mkv -map_metadata 0 -map 0 -c:v libx264 -crf 0 -preset fast -vf "fieldmatch=order=tff:combmatch=full, bwdif=deint=interlaced" 1min_264_deint.mkv and the same behavior is present (still frame at the end, lots of skipped frames)

I've also tried reencoding the deinterlaced video: ffmpeg -i A1_t00_deint.mkv -c:v ffv1 -map 0 -map_metadata 0 A1_t00_deint_reenc.mkv This also made no difference.

[BlueSwordM]

I only have one question: have you tried using different chunking methods?

ffmpeg hybrid is known to cause such issues, while ffms2 and lsmash aren't.

[OParczyk]

No I have not. I've just tested select and (apparently unsurprisingly) the output looks the same. I'll try and setup lsmash and ffms2 and report back.

[OParczyk]

I've managed to set them up now.

select and hybrid result in the same video: lsmash makes the problem even worse, doesn't even get the first few frames right and also has a still frame at the end: ffms2 desyncs too, but doesn't seem to result in still frames: just for completeness I've also tried segment, but that made av1an crash.