Sound compression problem??

[wolfvgang]

Ok, I'm starting to learn how to do this:
Video : FitCD -> Avisynth -> ProCoder Express - mpeg2
Audio : Virtualdubmod -> wav -> ffmpgegui -> ac3
Author : GUIforDVDAuthor

But in the meantime I have a nice DivX --> DVD converted DVD sitting on my desktop with an audio problem. I made it using Xilisoft DivX to DVD convertor, and the video is fine. However, the audio has this weird digitalized background sound to it...like a computer sound...sort of like pixelated audio...I don't know what to properly call it. The sound is also kind of hollow-sounding.
I think maybe it's due to the bitrate of the sound or something...but I'm a newbie, what do I know?

Is there a way to clean the sound up from the files I already have in the DVD folder I made, without starting all over? I searched around and all everyone talks about is sync problems, or hiss, or pops...that is not the problem here.
Thanks in advance.

[redwudz]

Another great freeware tool is the audio editor Audacity. It accepts WAV, MP3, Ogg and AIFF audio files. It has quite a few filters, just play with them a little. If you need to output MP3, you need the Lame MP3 codec in your system. If the audio is already in the DVD file, you would have to mux it out to use Audacity. Better to use it when you have the audio in WAV format.

[wolfvgang]

thanks for the response...so it sounds like I need to demux the audio out of the DVD files to fix it? is there a guide on how to do that I'm not seeing? If not, can somebody tell me how? Thank you

[guns1inger]

What you are describing sounds to me like the results of compressing the audio too much. If this is the cause, there is little you can do to repair it. Most of the filters that would smooth things out will only leave you with a dull, lifeless audio track.

[redwudz]

If you were to use Audacity, you would need probably WAV format. You can use VirtualDub Mod and drop each VOB in there and save out the audio as a WAV. If it is AC3, you would need the AC3 ACM Decompressor installed. Probably better would be to use VOB2MPEG first and just have one big MPEG file.

After you process the audio, you would have to mux it back into the video. If the video were VOB format, I haven't tried that, so I'm not much help there. That's why I process the audio before making a DVD.

What I have done instead, right or wrong, is to use VOB2MPEG to save out the entire DVD video to a separate hard drive. Then I save out the the audio as a WAV with VD Mod, then process that with Audacity, encode back to AC3 and add it back with the MPEG-2 video in TMPGEnc DVD Author and reauthor the whole thing. You could use GUIforDVDAuthor if it will accept elemental streams of audio and video. Otherwise you would have to mux the audio and video first before authoring.

It's probably faster to re-encode the whole thing instead, but I had deleted the Xvid files.

I'm sure there are better ways, but I've only needed to do that once, so I never tried to find any.

[wolfvgang]

Thanks for your replies, they were helpful. Your right, the audio was compressed too much, and it was faster just to re-encode.

What I ended up doing was re-encoding the DivX to DVD using ConvertxDvd on a whim. I got a perfect copy. So far it seems to be working well with all my videos. Yea!

My only gripe is the inability to make menus with navigation buttons in ConvertX. It makes a menu, but not one with navigation buttons. I briefly tried doing that in GUIforDVDAuthor but it wanted re-mux the whole thing - and that made the video choppy. GUIforDVDAuthor only works well with seperate audio and video elemental streams in my experiments.
I know that I can actually encode the DivX with other programs like TEMPGenc into two separate streams for the GUIforDVDAuthor, but is there a program or method where I can just create a clickable menu and insert it into the already encoded DVD?
Many thanks,
~W

[machf]

Doubtful. You could replace an existing menu, at most (manono just posted a guide for that here).

Can't ffmpeg be used to demux MPEG files? That way you would have the elementary streams you need. Or, if you have a DVD tructure (.VOB, .IFO files), you can use PGCdemux too.