Re: [transcode-devel] A/V sync problem transcoding from .nuv to .mpeg

[Steve Hosgood]

Andrew Church wrote: (sound seems to be getting later by 1 or 2 seconds per minute). Well, it looks like this is because NuppelVideo is one of those horrid variable-FPS file formats; in fact, it makes no attempt whatsoever to keep a constant frame rate! Actually, to be fair, Nuppelvideo is probably trying to make the best of a bad job. The capture card is a Brooktree BT848 and apart from doing PAL-decoding (or NTSC) it does almost nothing other than chuck frames at the computer over the PCI bus. I've got a 1600MHz machine, but even then it can drop the odd frame here and there. Especially in this case where the video was coming from a VHS recorder already. It might have been better had I captured direct from broadcast, but I don't have the computer in the same room as the TV decoders/tuners/whatever. In the sample file you put up, the time between frames varies from 40ms (true 25fps video) to 78ms (a dropped frame minus 2 milliseconds). That's why the A/V sync falls out: the NUV import module doesn't pay attention to the frame timestamps, so for every frame that lags or gets dropped, the audio and video get more and more out of sync. Again, Nuppelvideo did at least allow for the chance that it might drop frames - it timestamped them, and 'transcode' ignored that part of the spec! I've done a partial rewrite of import_nuv in CVS HEAD that checks the timestamps and clones frames as needed to keep sync; could you try it out and let me know if it works? --Andrew Church [EMAIL PROTECTED] http://achurch.org/ Certainly - thanks very much for such a prompt attack on the problem. (Or, judging by your website, maybe that should be "domo arigato gozaimashita"!) I'll just have to set up a CVS checkout. I got the last lot of sources as a tarball off the website. Steve