sudden switch from 5.1 AC3 to 2.0 AC3 in mpeg2 file??

[sohr]

Hi,

I have a few high-def recordings that I've been archiving to DVD.

I usually like to edit these mpeg2 captures with MPEG2-VCR, which is a great tool. However, on of my files, I noticed that the sound cuts out complelety when I play it using MPEG2-VCR right after the first commercial blank.

When I play the same file with just about any other player, I get no such cut out.

I ended up using VideoReDo to edit the file because of this. I split the file up into two seperate files based on time. I noticed that GSpot, VideoRedo, and AviCodec all tell me that that both the original file and the one of the edited files contain an 2.0 channel AC3 track at 384 kbps. However, the other edited file contains a 5.1 channel AC3 track at 448 kbps.

This is all strange, since the whole broadcast was supposed to have 5.1 channel audio. I'm now wondering if this is why MPEG2-VCR cuts out after the first commercial break in my original file-- perhaps the broadcaster changed the audio format being broadcast?

In any case, is there someway to view what the audio stream format is at any given point in time in an MPEG2 file? Or must the whole file have the same stream format? If that's the cause... I'm not sure how I was able to get a file with 5.1 channel sound out of the original file which GSpot tells me only had a 2.0 channel AC3 track.

Any ideas?

Thanks,
James

[sohr]

Well, I'll answer my own question here in case someone in the future runs into the same issue.

It turns out the local broadcaster did change the audio feed from 5.1 to 2.0 channel sound during their own allotment of local affiliate commercial space. This whacked MPEG-VCR and several other decoders up.

The solution was just to use VideoReDo and edit out the local commercials-- however, in order to get it to work right, I had to also remove a few frames before and after the commercials.

After the editing, I now have a file with 5.1 channel sound, out of a file that GSpot, MPEG-VCR, AviSynth, and TMPEG all said only had a 2.0 channel audio stream.