Saving audio only when saving/rendering AVI

MoreK wrote on 9/25/2002, 10:09 AM
I'm working with DivX coded AVI files with uncompressed audio.

Is there any way to do modifications to audio and then save AVI with modified audio only. I don't want to recompress video just because of few modifications to audio. Any suggestions? If Vegas Video can't do it, is there any other tools or programs that can?

Thanks, MoreK

Comments

haywire wrote on 9/26/2002, 12:20 PM
When I have a small audio change to make, I render the section to .wav (render to new track to keep things in sync) then place the new .wav file on the timeline and re-render the entire project to .avi. Once you've verified that everything is ok, you can deleted the old .avi file to save disk space. If you make no changes to the video, the rendering time is minimal.

Michael
Chienworks wrote on 9/26/2002, 9:21 PM
The problem in this case is that the source is DivX, which means that Vegas will uncompress it to work on it, then recompress it to save it to the new file. As far as i know, the only two formats that Vegas can handle natively without decompression/recompression are DV avi and uncompressed avi.
mikkie wrote on 9/27/2002, 11:35 AM
Most editors, VV3 included, will not re-render any unchanged avi files where the picture is stored per frame, like with pic video or morgan or quicktime motion jpeg etc. The problem as you've said comes when you try to use something like most mpeg2 (you can use all keyframe - I think), wmv, real, &/or divx.

The two solutions I'm aware of are to alter the file(s) before compressing them to divx or use multiplexing software that basically strips the audio & replaces it with another audio stream. Virtual Dub used to be able to handle divx, but I'm unsure if there's a version that will do a direct stream with the latest divx codec. Check out the freeware & faqs etc. at digital-digest.com -- I'm sure you'll find something, though it may be a combo of programs, command line stuff and so on. It's been a while but if I remember correctly, TMPEGEnc has a utility built in that will handle the multiplexing also, but again you'd have to check it out -- now that divx has their pro version I don't know if anyone's backing off support or not?
MoreK wrote on 9/27/2002, 3:23 PM
Hey thanks a lot. Funny thing is I downloaded VirtualDub couple of weeks ago, and have used it for capturing video. But I never realized it had these cababalities.

I tested it with DivX 4.2, it seem to work fine. I can a) save audio to .WAV b) edit it in Sound Forge c) save it d) import it to AVI in VirtualDub e) save AVI with new audio without rendering the video.

Audio seem to be in sync. The only thing I'm little worried is the file size. It slightly differs from original. Altough audio is uncompressed in the original AVI and I don't change it's characteristics (bit rate, length...). It's exactly the same size when I import it to AVI.....
mikkie wrote on 9/28/2002, 10:21 AM
You'll get slight variations in the length of avi files depending on which software does the writing, I *think* because of the ways they write the file headers and stuff. In fact I've used V/dub just for that purpose, rewriting the avi file when I get a rendered avi that another program won't accept, I guess because something in the headers is off spec.

Stuff I've come across to mention: If you have a choice, interleave audio on a per frame basis rather then time if you think you might open the file in another app, and I usually set the preload for audio at 0.