[MEncoder-users] a/v desync when encoding combined 24000/1001 30000/1 fps NTSC DVD

belcampo belcampo at zonnet.nl
Thu Feb 26 13:17:09 CET 2009

Sergey Kovalev wrote:
> belcampo wrote:
>> Sergey Kovalev wrote:
>>> But when I encode audio reducing abitrate, I do two-pass encoding with 
>>> a shell script:
>>> mencoder dvd://1 -chapter 3-3 -aid 129 \
>>>      -ofps 24000/1001 -oac lavc -o $fname -ovc lavc -lavcopts \
>>>      vcodec=mpeg4:vbitrate=1152:mbd=2:trell:v4mv:autoaspect:vpass=$i \
>>>      -vf pullup,softskip,crop=656:352:32:64
>>> where $fname and $i are shell variables with corresponding values.
>>> The resulting avi shows enormous a/v desync:
>>> A:15869.7 V:  25.9 A-V:15843.711 ct:  2.590 622/622  5%  1%  0.6% 0 0
>>> if I understand A:, V: and A-V: numbers correctly. Seeking on audio 
>>> stream is almost impossible. And forward seeking often leads to warnings:
>>> Badly interleaved AVI file detected - switching to -ni mode...
>>> Besides ct: value is always growing. That leads to the actual desync 
>>> which can only be avoided by using -mc 0 while playing.
>> I think you'll endup by dividing video and audio encoding then remuxing 
>> to what you  want.
>> In the end your sources are time x of video and time x audio. If you get 
>> a/v sync at the beginning it will be there at the end.
> I made some more testing and found out that when I encode audio with 
> "-oac lavc", the afore-mentioned desync appears, but whan I use "-oac 
> mp3lame -lameopts cbr:bitrate=224" syncing is done right.
> Is it a bug or I've missed some option?
> Also I don't understand what options "-vf pullup,softskip" do (which I 
> took from documentation as advised), because without them I don't see 
> any glitches in encoded video as with them.
> Probably my original video is not telecined. I don't know what to 
> suppose else.
Probably read up on
to better understand what problem you can solve with what tool/mencoder 
option. Furher the less the better, according to myself ;-)
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