Loading 5.1 AC3 files into Vegas

LJA wrote on 8/19/2007, 9:34 AM
Perhaps many of you know this technique already, but the question has been asked in the forum several times that I know of and the answer has always been "it can't be done". Well, that is true, but...

I accidentally discovered this trick today:

1. Multiplex your AC3 file with any video. I used five seconds of black and multiplexed with MPEG-VCR.

2. Load the resulting MPEG file into Vegas. Vegas will create five tracks: video (five seconds of black) and four audio tracks (Front L & R, Center, LFE, and Rear L & R).

3. Delete the dummy (blank) video track.

You now have added previously recorded/rendered full 5.1 surround to your project. I hope this helps anyone who as puzzled as I about how to move AC3 files around in Vegas. Of course this works for stereo AC3 files also.

If you want to mix several 5.1 or stereo tracks, this is hardly ideal; multiple encodings with their implied quality reductions would be involved. But occasionally I find that I have as many as ten or twelve audio tracks in a project and preview playback suffers. So I render the audio separately and use this technique to play a version of my project with just the video and the AC3. I get a much better feel for the final project this way.

Comments

Sol M. wrote on 8/19/2007, 3:15 PM
I for one did not know about this. Very useful info. Thanks :)
DJPadre wrote on 8/19/2007, 4:58 PM
afew things to note.

this ONLY works in V7

to get an effective 5.1 mix close to the original, you must use the same panning parameters (constant, square or film suround placement

when re-rendering turn OFF any additional DR compression (ie film light/medium)

When rerendering make sure you use -31 dialogue normalisation, as the original has already been set to -27 (from camcorder) or depending on how the original was encoded to begin with

Despite the full 20khz range when using 5.1, compression has already taken place. In turn, additional compression WILL affect the sound quality but not to a point of being noticable.
Only with spectral analysis will u be able to decipher the differences, and of course the sound system in which the actual file is being played back on. On a high end system, slight compression will be heard (like MP3) but on an average ssytem,, it wont even be noticable