[FFmpeg-user] Slide show with vfr

[Mark Filipak (ffmpeg)]

On 01/25/2021 06:09 AM, Wolfgang Hugemann wrote:
>> Express duration in seconds
>> Repeat the last image as per
>> https://trac.ffmpeg.org/wiki/Slideshow#Concatdemuxer
> 
> Thanks for this hint. This really works and -vsync vfr seems to be
> necessary for mp4. (For mkv it works without that.)
> 
> It works as well if you provide the durations in milliseconds, but there
> seems to be a problem with short durations, which are not reproduced
> exactly. So one should rather use durations larger than one second, as
> in the cited example.
> 
> I now successfully produced a vfr mp4 with ffmpeg. Indeed, some
> applications as VLC do not handle the timestamps correctly, but AVidemux
> and ffplay do. Plus the vfr is preserved when the slide show is
> processed with ffmpeg (using -vsync vfr).
> 
> Possibly, the relatively short durations in my original video are the
> reason for the problems with the original video, as there seem to be
> rounding errors.
> 
> Wolfgang Hugemann

I have not been following this thread as it doesn't interest me or apply to my use cases, however, 
regarding PTS variations, I've often found that simply remuxing an existing stream via MKVToolNix 
has fixed the time stamps so that all players play videos correctly. Bonus: The result is usually 
slightly smaller and MKVToolNix is very quick. I don't know what MKVToolNix is doing, but it's 
brilliant.

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