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Old 11th April 2010, 15:26   #1  |  Link
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Correct process chain to avoid audio sync issues in HDTV rip

Hi, I don't know if this is the right place to post, if there is not, first sorry for mis-location and then please move this thread to the right section.

I'm having serious audio/video sync problem when trying to encode DVB-S2 stream to xvid.

Please consider this situation:

file1.ts and file2.ts contain avc video and ac3 audio

I apply the following process chain:

file1.ts -> DGAVCIndex -> file1.dga + demux_audio1.ac3 (with some delay)
demux_audio1.ac3 -> BeSweet -> audio1.wav (with 0 delay)
audio1.wav + file1.dga -> AviSynth (with uNicAudio.dll) -> VirtualDubMOD -> check for audio sync/crop/resize etc (and everything is ok)

Same process for file2.ts

I tried to have a xvid coding of file1 only and file2 only and they are perfectly synched

I got a desync when I tried the following avisynth script

VIDEO1 = AVCsource ("file1.dga")
VIDEO2 = AVCSource ("file2.dga")
AUDIO1 = UnicAudioSource("audio1.wav")
AUDIO2 = UnicAudioSource("audio2.wav")
FULL1 = audiodub(VIDEO1, AUDIO1)
FULL2 = audiodub(VIDEO2, AUDIO2)
return FULL1+FULL2

Desynch occurs at file junction, but, as I said, if I encode only file1.ts or file2.ts resulting avi files are perfectly in synch

Can anyone tell me if there is some process step I'm not considering?
I guess it is related of some audio processing/joining problem (I mean, if first audio duration is lower then first video duration because of delay trimming, probably when joining together the two files the audio stream are joined without considering gap between video1 and audio1)

Can anyone please explain me if there is a more convenient way to do what I'm trying to obtain?

Is there a better process chain to follow? (considering that control and understatement of any step is a need, I don't like the all-in-one software)
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Old 11th April 2010, 18:39   #2  |  Link
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your audio1 is shorter or longer than the video1...use this (it will reset the audio length to the video length):

FULL1 = audiodub(VIDEO1, AUDIO1).Trim(0,0)
FULL2 = audiodub(VIDEO2, AUDIO2).Trim(0,0)
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Old 11th April 2010, 22:37   #3  |  Link
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replace FULL1+FULL2 with FULL1++FULL2
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audio sync, avc, dgavcindex, hdtv

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