[MEncoder-users] a/v desync when encoding combined 24000/1001 30000/1 fps NTSC DVD
jimht at shaw.ca
Thu Feb 26 14:04:47 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 ;-)
Another suggestion: stick a harddup at the end of your video filters.
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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