How do I demux an MP3 from a DiVX file?

[dvdyke]

Do not suggest VirtualDub or Nandub etc. Although you can save as a wave file on the file menu and rename it to .MP3 It saves it with it's wave file header. I need to save it back as an original valid MPEG1 Layer III file so I can apply MP3AMP on it (MP3AMP amplifys the volume without recompressing the MP3). But at present MP3AMP reports any files I saved in VirtualDub/Nandub as non-valid layer III MP3 files. Also if played in Winamp then viewing the file information it thinks it's MPEG1 layer 1.

I tried to hex edit the wave riff header out but it still doesn't seem to work.

Any ideas?

[manono]

Hi-I've never tried this but it should work.

Download WaveMP3 from the audio section of Doom9's download page. It was designed to add a wave header, but also has a feature to strip the wave header back out.

[dvdyke]

Yup! Tried that. Wavemp3 reports that the file is not a valid MPEG1 Layer III file. I've tried saving the WAV in Nandub, Vdub and Vdub-MP3-Antifreeze with the same result. I don't know what The dubs do to the audio but it screws the file for some reason. I can rename it to .MP3 or leave it as .WAV and it plays back fine in Winamp etc. But trying to get MP3AMP or Wavemp3 to recognise it as either a valid WAV of a valid MP3 is no go. Any other ideas?

[Schultz]

If you used Nandub to mux in a mp3 straight without giving it a wav header you might wanna read the latest news from Avery, this might be your problem but then again it might not...
http://www.virtualdub.org/virtualdub_news

[manono]

Hi-I got curious about your problem and tried to duplicate it. In Save WAV, if I entered "AudioFile", or "AudioFile.wav", I had the same problem as you. But if I originally named it "AudioFile.mp3", then there was no problem. It behaved in every way as a true MP3 file. I did, however have a synch issue when trying to remux it later. Perhaps it was because of what Schultz alluded to above, or perhaps because it was a VBR MP3 originally, I don't know. But are you putting on the .mp3 extension when you demux it?

If worse comes to worse, I think you can always decode it with Exact Audio Copy or something, and normalize the resulting .wav file before reencoding with Lame.

[dvdyke]

I used Graphedit in the end to demux it and it works perfectly. Now I can increase the volume of an MP3 without recompression or quality loss :)