AV1 video framerate issues

Help
1

I’ve been encoding my Blu-Ray collection to AV1 with the SVT-AV1 encoder. The encoder outputs ivf files. I can use mkvmerge to merge these files with audio tracks, subs, and chapters. The resulting file plays correctly

mkvmerge -o "S04E084 - The Light.mkv" video.ivf audio.m4a --language 0:eng english.sup --chapters chapters.txt

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If I use mkvextract to extract the AV1 stream, and merge it into another mkv file, the video’s FPS is doubled, even though it reports 24000/1001. The other streams play correctly. Using the --default-duration option for the video stream doesn’t fix this.

mkvextract 'S04E084 - The Light.mkv' tracks 0:video.ivf

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If I use ffmpeg to extract the AV1 stream, and merge the video into another mkv file using mkvmerge, the video’s FPS are also doubled, however, using the --default-duration option does fix the issue.

ffmpeg -i 'S04E084 - The Light.mkv' -map 0:0 -c:v copy 'video.ivf'

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Am I missing an option for extracting AV1 files with mkvextract? Or should I be using a different option for mkvmerge?

2

Welcome!

It’s quite possible that the extraction into IVF handles the track’s default duration wrongly. Please open an issue over on Codeberg for it. Otherwise chances are I might forget about it again.

I’d also be good to have a concrete file for which this happens, meaning the original IVF before merging it into Matroska for the first time. Please upload one such file to my file server. It doesn’t have to be that long; you can cut off the first 20 MB or so from the file with dd.

Thanks.

3

I opened the issue here

4

Thank you very much!