How do I make a stereo AC3 know it is stereo?

[mitsubishi]

Hi, I don't really like asking dumb questions around here, since I know you people don't like it. :p

But... I record quite a bit of stuff off BBC HD and transcode to 720p for storage. If it's 5.1 I'm pretty certain I should leave it alone, but often it's just 2 channel, so the bitrate seems a little excessive, coming in at 160MB an hour.

Also sometimes it has 6 channel right at the start if I cut it just as it switches. This doesn't seem to bother normal playback, but upsets my bluetooth headphones as at the change they go to turn off, come straight back on, but are then slightly behind until I seek.

I also just noticed, I have a cut piece of audio which seems to be stereo right through, but if I open in MPC and look at properties
Audio: Dolby AC3 48000Hz 6ch 384Kbps [AC3]
But the muxed mkv with the audio and video says this:
Audio: Dolby AC3 48000Hz stereo [Audio]

I thought I could sort out the 6 then 2 problem by cutting a little after and then inserting silence, but couldn't figure out the besweet command line. (BTW I've been using besplit to cut the audio)

Any links/suggestion or general comments welcome :cool:

[mitsubishi]

I had the same thing happen again on another file, but this time it still said it was 6ch after muxing. However, unlike the first case where only my headphones went out of sync, it also happened with MPC, no noise or anything, just out of sync until I seeked. It didn't happen with VLC though.

But I found what I was looking for, I cut 200ms later, missing off the 6ch bit, then added the delay with "delaycut"

http://jsoto.posunplugged.com/audiotools.htm