Audio CBR out of sync after muxing + stuff

[Darius_bd]

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Hi there ppl of videohelp. Indeed you have been a great help for over a year with your many guides, yet now I'm a bit lost. See, I wanted to convert an avi to mp4 so I can see it on my cellphone [SE w300: xvid isma + lc-acc] and I follow this steps:

- Demux the audio out of the video [cbr mp3] and disabling the stream
- Apply resize and rotate filters and change the fps [to 20], and compression [xvid, Lv3 200kbps]
- Converting the mp3 into lc-acc with nero wave editor
- Converting the xvid into isma and then muxing the mp4+acc into mp4 with YAMB.

After I do that, the audio is out of sync, delayed. I know VBR mp3 makes this kind of problem, but this is a CBR... could be the change of framerate? The original is 23,9. If it ain't, then I'm very lost.

[Or can VirtualDub Mod encode the audio into lc-acc? That would be great]

And another thing, which program should I use to hardcode subs into the vid?? I need one that can add subtitles rotated... is there any?

Many Thks!!

[poisondeathray]

Virtualdub / Virtualdubmod do not support AAC

Just do the whole thing in Avidemux, including encoding, resize, fps change, audio, rotating & subs.

Apply the sub filter before rotating

Avidemux will build a VBR mp3 time map, so don't worry about sync issues

(Beware subs will look tiny and crappy on a tiny screen)

EDIT: You have to use avisynth to make the video fps=20. The internal assumefps and fps set of avidemux is not as precise as using avisynth. For example, if the audio is 95 minutes, it stays that duration, you have to adjust the video fps to match and keep the exact duration (eg. 95 minutes) to sync. I tried this out and the script that worked for me was:

DirectShowSource("C:\PATH\MOVIE.AVI",fps=20,conver tfps=true, audio=false)

You can feed this into avidemux through aviproxygui, and do all your filtering, rotating, hardsubbing, encoding of the video in there. Alternatively, you could probably do all your editing through scripts. (Actually come to think of it, you could probably filter, rotate, hardsub and encode with virtualdub as well)

You have to do the audio separately (any encoder like Nero AAC, or even avidemux, but then separating the audio), then mux the audio with YAMB or even through avidemux (specifying the demuxed audio track)

[Darius_bd]

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Thks! I think... in the end you tell me to do what I'm already doing n_n but I don't get how the audio gets out of sync.

Btw, I made a mistake, the video is delayed compared to the audio. So I'm more lost than before... what am I doing wrong that a cbr got out of sync?

[Midzuki]

Darius_bd wrote:

the video is delayed compared to the audio. So I'm more lost than before...
what am I doing wrong that a cbr got out of sync?

It looks like the framerate conversion was done incorrectly.
23.976fps to 20fps should imply frame-dropping, but the application
you used has chosen slowing down the playback rate, apparently. HTH.

[poisondeathray]

Did you use the script? The internal filters of Vdub and avidemux didn't work for me. (I also used Nero AAC for the audio); this combination worked for me in sync on a small clip.

Check the durations of audio & video beforehand to identify where the problem is. e.g. If it was 29min5sec before, it should be 29min5sec after.

Also check if its constant delay vs. worsening delay. You can fix constant delay very easy.