Audio present on VOBs, but missing on burned DVD?!

[jkn]

Hi all
I've been using my gentoo system to burn a DVD, captured from VHS tape. My normal DVD burning sequence goes something like this (depending on source material):

- projectX
- mplex
- dvdauthor
- K3b

For this project, because it was capturing from tape, and also because it was an NTSC tape and I wanted to convert it to PAL (I'm in the UK), it was a little different. So I had to do some resampling and cropping/resizing etc. But after some work with AviDemux, I ended up with an mpeg program stream file, which plays fine under VLC

I then ran dvdauthor and burned the DVD with k3b - no problems.

However, when I play it on a DVD player, after around 70 mins (of a 100min recording), the audio disappears, and does not return!

Using VLC, the audio is present throughout, on both the mpeg and all the VOBs dvdauthor has created. I've burned a couple of DVDs with the same result. The audio is in sync when it disappears, and the video continues fine after this point.

I don't understand how the audio can be present on the VOBs and then disappear like this. It occurs about 1/3rd of the way into one of the VOBs as well, rather than at the beginning of a VOB.

I've tried playing the DVD on my PC with VLC with a similar result.

Any clues as to what might be happening? I've never had trouble with k3b before and it seems a very odd problem not to have seen before.

Thanks for any thoughts

jon N