[Cin] Audio out of sync when rendering MP4s

[Terje J. Hanssen]

Den 31.01.2024 11:27, skrev Matteo Bini via Cin:
> Hello Cinelerra GG developers,
> I've found a strange behaviour in this great editing software.
>
> When I render my project, sometimes the audio is out of sync. Not all
> the audio, but from a certain point, from half of the video the audio is
> out of sync and it gets worst the more we get to the end of the video.
> It's like latency piles up. I've only done MP4 renderings so far.
>
> My idea, but I don't know how to demonstrate it, is that ffmpeg doesn't
> know how to render audio and video in sync, when there's some audio that
> is not aligned on frames. Since I do a lot of precise audio editing in
> my project, there are some audio cuts that are not aligned on frames.
>
> It's not a big problem, I just wanted to let you know. The solution is
> very simple: render only the video track, then render the audio track in
> WAV and then mux them together with ffmpeg, copying the video track and
> encoding the audio one. This way the video is perfectly in sync with the
> audio.
>
> The strange thing is that, when I watch my project from the compositor
> window, audio and video are in sync.
>
> Thank you for making Cinelerra GG a really great free software.
>
> --
> Matteo Bini

Hi Matteo,

Sorry 'I can't help other than tip about a similar thread on the old 
CinCVS mail archive:
https://www.mail-archive.com/cinelerra@skolelinux.no/msg04730.html
https://www.mail-archive.com/search?l=cinelerra%40skolelinux.no&q=audio+sync+problem+on+rendered+output&x=0&y=0