[FFmpeg-devel] [BUG] transcode DVD films have a/v sync issue

Limin Wang lance.lmwang
Wed Sep 12 06:12:58 CEST 2007


> On Tue, Sep 11, 2007 at 07:19:25PM +0800, Limin Wang wrote:
> > Hi,
> > 
> > I'm try to transcode some dvd to ts(h264) by ffmpeg, if the dvd is DVD films,
> > the output will lose A/V sync and video can't play smoothly.
> > 
> > Below is simple command line to reproduce it:
> > lmwang at test1-desktop:~/dev/ffmpeg$ ./ffmpeg -i
> > /home/lmwang/bitstream/24fps.vob -b 1500kb -bf 3 -coder 1 -refs 4 -partitions
> > all -vcodec libx264 -ab 96kb -ar 48000 -ac 2 -acodec mp2
> > /mnt/dvd_result/test_1500kb.ts
> our mpeg ts muxer is broken, it writes random timesamps (yes i verified that
> the dts/pts ffmpeg feeds into the muxer are quite different from the totally
> nonsensical dts/pts that our mpeg ts demuxer returns)
> use mpeg-ps and -vsync 0 it works, without -vsync 0 your output will be
> full of duplicated frames, though it works as well if your system is fast
> enough

So when we need to enable vsync?  what's the purpose of vsync?  why vsync is
enable default, but async is disable default? 

> if you want to fix the mpeg ts muxer look at the patches from xiaohui
> (some on the mailinglist some in the soc svn) and help cleaning them up
> maybe they fix the timestamps

OK, I'll try to search these patches to get some basic understanding.


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