I've noticed that certain video source files seem to trigger weird behaviour in D-o-m: the audio is thrown off sync when exporting to file – but not when creating a DCP from the same file, from the same project, with the same settings.
Case:
I've received a short film as an mp4 (h.264/AAC) file
I create a new project in D-o-m and import the mp4
I trim it to 30 seconds (just to make this test run quicker; all other settings remain at defaults)
I create a DCP: audio sync matches the source file exactly
I export to a ProRes file: audio is 5 frames late
I've experienced this with several mp4 and ProRes files from various sources. I can't seem to find anything out of the ordinary in these files, but the problem does disappear if I put them through a simple "ffmpeg -i infile.mp4 -c copy outfile.mp4".
The files are copyrighted material, but I can PM a download link on request.
It went back and forth, and maybe some of these issues are solved for the DCP, but not the export. Personally I never had audio sync issues, it is weird that some audio files use these strange capabilities. Wondering wether this could actually be a sick copy protection method.
You could try to reimport the created DCP into DCP-o-matic and export this to Prores. Of course your FFMPEG in-out copy is the better way.
Last edited by Carsten on Wed Mar 17, 2021 10:38 am, edited 2 times in total.
OK, so it was a known issue – thanks! I just run a quick test on 2.15.135, and it seems to be fixed all right.
Carsten wrote: ↑Tue Mar 16, 2021 10:49 pmYou could try to reimport the created DCP into DCP-o-matic and export this to Prores.
This wouldn't have worked for me in this case, as it will introduce a color shift. I've always assumed it to be a more-or-less inevitable side effect of RGB –> YUV –> RGB conversion, so I haven't filed a bug report
