Help needed with off-sync VBR audio and video when muxed

[20/20]

HI,

I want to understand why vbr-mp3 cannot play in-sync with my xvid video..

I re-coded this XVID-video to a smaller size (refurbished picture, changed resolution, and re-encoded withh lower bitrate)
If I just demux the MP3 and mux this with the new re-coded video. All plays in-sync.

But, when I demux MP3 and transcode it ( from 192 CBR 44.1KHz
-> 80 VBR 32KHz), and mux this with the video. It plays out of sync.

Why is this, and what can I do to fix it?

[20/20]

commandline for the lame-vbr-mp3 is:

-b 32 -m f -V 4 -B 112 --vbr-new --lowpass 14
(with this low rate, sampling feq. gets defaulted to 32KHz, dunno if this has anything to do with off-sync audio when muxed)

[redwudz]

I'm not sure exactly why that happens, but I always save out VBR audio with VirtualDub Mod, with full processing as a WAV file, then convert that to MP3 CBR if needed and add it back with the video. No sync problems that way. It may be the programs not being able to read the length of VBR audio when re-encoding it directly is causing the problem.

[20/20]

Ok. So demuxing the audio with virtualdub in "full processing mode",
then save it as CBR-MP3 could fix the sync-problems.
I'm gonna try that.

Also, I opened up the original video with Avi-Mux, then I saw this behind the audiostream:

"CBR 192kbps, 2Ch, 44100Hz, bad: 626, delay 26ms, 150Mbyte"

Because it said the audio had delay, I tried to mux with that delay. Wich did not help.
But do you know what this "bad: 626" means?

[redwudz]

Actually, my method isn't demuxing with VirtualDub Mod, it's converting the VBR audio to a different format using full processing, to WAV audio. Demux usually means you are just splitting the audio off from the video, without changing it. That never worked for me with VBR audio. VD Mod also works better with audio than the regular VD, IMO.

VirtualDub Mod can encode the converted WAV audio back to MP3 CBR if you add the WAV back in and use full processing to MP3 CBR on the audio and direct stream processing with the video and output as a new file. I usually use Lame MP3 in VD Mod for MP3 CBR encoding. I haven't used Lame as a commandline program, so I'm no help there.

Or you can convert the WAV to MP3 CBR with other external programs, then add it back with the video using VD Mod. If you do this, you can just use direct stream copy with both audio and video, as you aren't doing any encoding. That's a 'mux'.

Converting to WAV audio first is what seems to fix the sync problems with VBR audio. If I'm going to encode a AVI type file with VBR audio to MPEG, I just use the converted WAV audio as is, and let the MPEG encoder convert it. Or I use ffmpeggui to convert the WAV audio to AC3 and put the audio and MPEG video into my authoring program.