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Subject: 5.1 AC3 bleed to rear speakers when using stereo source
Posted by: Billy d
Date: 2/16/2005 2:52:12 PM

I have come across a problem that I have been unable to solve with Vegas 5.
If I record a voice commentary in mono it will play back from the front 3 speakers using the 5.1 pan controls and sound fine as if it were centred. But if I record a commentary in stereo (using a separate DAT machene and transferring to a stereo wav file using SoundForge) and pan it using the 5.1 pan controls to the front 3 speakers the same as for the mono commentary, the voice "bleeds" onto both the rear speakers at a low but clearly audible level. This makes the voice sound very odd. According to the 5.1 pan controls the rear speakers are at -inf, and therefore should not have any signal from the stereo commentary at all.
Using a direct feed (not encoding in AC3) Vegas5 does the right thing with the stereo signal and gives no bleed onto the rear speakers. But when I encode into 5.1 AC3 the bleed is back.
This happens both from my Audigy 2 card using Vegas and from a DVD burned using DVD Architect and played back on my separate DVD player feeding into my TV.
I have tried making the stereo into 2 separate mono signals and panning them hard left and hard right. Same problem, bleed. However if I mute one of these two mono signals the bleed disapears, but then I only get the sound from the left (or right) front speaker.
Is there a bug in the Dolby Digital 5.1 surround coder in Vegas 5?
Is there something else I can do, apart from recording everything in mono (a giant leap back to the 1960's)?

Subject: RE: 5.1 AC3 bleed to rear speakers when using stereo source
Reply by: Orcatek
Date: 2/19/2005 5:39:22 AM

In the panner tool, click the rear speakers to turn them off. That should work.

Subject: RE: 5.1 AC3 bleed to rear speakers when using stereo source
Reply by: Billy d
Date: 2/21/2005 10:43:36 AM

Thanks for the reply, but I have already tried that and it makes no difference.
I still get bleed to the rear speakers.

Subject: RE: 5.1 AC3 bleed to rear speakers when using stereo source
Reply by: RCourtney
Date: 2/21/2005 5:48:13 PM

Are you all the way forward in the pan?

DAT on a second bus? Could it be a higher level and showing up
more in the back?


Subject: RE: 5.1 AC3 bleed to rear speakers when using stereo source
Reply by: Billy d
Date: 2/28/2005 10:54:23 AM

Yes I'm all the way forward. Centre and Front 100%. The rear speakers in the surround pan control show -inf, but even turning them off makes no difference. I still get the same level of bleed.
The bleed happens even with just a single stereo track and no other audio tracks. It's masked a bit when I'm using multiple stereo tracks with some of them panned towards the rear, but the bleed is still there from the 100% panned forward track. It's just not as obvious.

Subject: RE: 5.1 AC3 bleed to rear speakers when using stereo source
Reply by: B_JM
Date: 2/28/2005 6:15:28 PM

stereo tracks ? have you tried using mono tracks ?

I checked and any bleed is just above the noise floor ...

Subject: RE: 5.1 AC3 bleed to rear speakers when using stereo source
Reply by: Billy d
Date: 3/1/2005 5:11:54 PM

Yes, a single mono track panned hard front left or right produces no bleed. The moment I put two mono tracks, one panned front left the other front right, I get bleed.
You must have a high noise floor. Just kidding :-)

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