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

James Hastings-Trew jimht at shaw.ca
Thu Feb 26 14:04:47 CET 2009

belcampo wrote:
> 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
> http://linux.die.net/man/1/mencoder
> to better understand what problem you can solve with what tool/mencoder 
> option. Furher the less the better, according to myself ;-)
Another suggestion: stick a harddup at the end of your video filters.

-vf pullup,softskip,crop=656:352:32:64,harddup

pullup,softskip is there to recover progressive frames from the DVD 
video stream. Is the DVD of a movie, or a TV show? If the original video 
is interlaced video, then remove the -ofps 24000/1001 and remove the 
pullup,softskip, and replace those with pp=lb, or yadif (de-interlacing 

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