Extracting audio from avi - only does first 13mins

[DBIV]

I'm trying to extract the audio from an .avi, which is in Windows Media Audio 2 format and so unplayable through Quicktime on a modern Mac. When run through ffmpegx, the process starts OK but then suddenly produces a deluge of "Error while decoding stream #0.1" and finishes early. The resulting file is only 13 minutes 18 seconds long, when the original soundtrack is 1 hour 30 minutes.

What am I doing wrong and how do I get the whole soundtrack?

Log information:

Input #0, avi, from '/Users/DBIV/Desktop/movie.avi':
Duration: 01:30:24.0, start: 0.000000, bitrate: 1360 kb/s
Stream #0.0, 25.00 fps(r): Video: msmpeg4v1, yuv420p, 720x480
Stream #0.1: Audio: wmav2, 48000 Hz, stereo, 160 kb/s
Output #0, ac3, to '/Users/DBIV/Desktop/movie.avi.ff.ac3':
Stream #0.0: Audio: ac3, 48000 Hz, 5:1, 448 kb/s
Stream mapping:
Stream #0.1 -> #0.0 [sync #0.0]

[Krispy Kritter]

I've never used that tool, but it sounds like the file is corrupt. You may want to look into checking the file for errors and/or fixing it if possible. Although I don't know which tools you can use on a MAC.

[DBIV]

Thanks for the reply, but the file is definitely not corrupt. It plays all the way through without a problem (either sound or vision) on VLC.

[redwudz]

It may not be a problem with the file, but VLC can play corrupted video with missing frames and you may not notice any problems. Since you have the running time where it quits, you might try to put it into a video editor that can go frame by frame and you might see a problem around the quitting point.

This thread would probably get more answers in our Mac Forum. Moving you.

And welcome to our forums.

[tomlee59]

Redwudz is right -- VLC has numerous enhancements to deal with errors. It can play files that are totally unplayable by, say, QT, and it can deftly hide some errors that would be visible/audible when played by other software. So, playability by VLC is not necessarily a sure-fire guarantee of file integrity. Of course, this is not the same as saying that you do have a corrupt file, but it does mean that it remains a possibility.

One trick that has occasionally (but not always) worked for me is to select a different target format. So, instead of ac3, choose something like MP2 or MP3 (or something else). Each of these transcoding modules has a different way of contending with errors, so you might find one that doesn't choke too badly on WMA2. Then, you can perform one final transcode into your final target format.

A bit cumbersome, yes, so keep this in reserve as a Plan C in case no one else offers a Plan A or Plan B.

[dnix71]

Since this is a Windows media file, it's corrupt by design
People who don't own Macs just don't understand.

If you rename the file with an avi extension (make a copy to rename), and give it to VLC to play, if the time markers or key frames are damaged/corrupt, VLC will warn you before playing it and offer to fix it.