Surround Sound

[Aaron Neitz]

IMHO maybe it’s best to hire out an mix house to do your 5.1. it’ll take less time, it’ll sound great, they’ll know how to properly balance channels (not a small thing to be overlooked), and they can provide you a properly downconverted Pro Logic stereo mixdown as well (which most HD programs require along with the 5.1).

[David Roth weiss]

Dear Hd,

What hardware do you have? Do you have a 5.1 ready sound card, 5 speakers and a subwoofer? If not, you’ll definely need to take Charlie’s recommendation.

DRW

[Delano Bryant]

Well, I have a supplier that has some reference monitors and a sub for sale. I was looking at the M-audio box. But the one we did have, had issues with MAC. Is this what most post houses are doing? Mixing down in Pro Tools and then bringing back into FCP to On-line to Digibeta.

[Paul Dickin]

Hi
Tou’re mixing your metaphors here 😉
5.1 AC3 audio is a DVD-only format, and is either multiplexed onto a playable DVD-Video, or stored on hard drive or DVD-ROM as data.

DigiBeta takes audio files on its 4 tracks in straightforward PCM digital format, which is different to the AC3 file format.
Final Cut Pro doesn’t allow the import of an AC3 5.1 audio track, so you can’t put it onto digibeta by Editing to Tape.

To put surround audio into a conventional video file format you have to use the Dolby Pro-Logic system, which is a pseudo-surround arrangement, depending on subtle phase relationships within a conventional PCM stereo audio track.

[Delano Bryant]

thank you for that info. So, if the broadcast carrier isn’t capable of receiving anything else from us except Digi Beta. We are installing a Sony HD deck to deliever our programs on. How do most people deliever 5.1 surround to broadcasters? is there a standard?

[Aaron Neitz]

Digibeta can record 4 channels of audio. So the best you can do is get a Pro-Logic stereo mix done. But even then, it’s typically just a simple stereo mix.

For most network HD delivery they’ll ask for a D5 with 8 channels of audio. So from the mix house will give you 7 aiff files that you tell FCP to lay off to each of the D5 channels discreetly. So 6 aiff’s for your 5.1 mix (lay off to channels 1-6) and a stereo aiff that’s the downmix (layoff to 7 and 8).

I don’t know about HDCAM – we’ve never delivered anything on it. I’m assuming it can do 8 channels of audio… but don’t quote me on it

[Jean-christophe Boulay]

At this sound studio, we deliver HD sound either on HDCAM or as a 5.1 mix on an MPEG-2 4:2:2 file when delivering electronically. Some broadcasters have asked for AC3 files as well. It really depends on the station’s acquisition standards. If I was to deliver to a video post house, I’d give them 6 AIFF files plus a stereo Lt/Rt (ProLogic) AIFF file. How they lay that down, I have no idea. For bigger productions, we deliver the mix on MO disk written with the Dolby DMU CPU, though that goes to a duplication house who work with about every format ever created by man.

The broadcasters probably have acquisition norms regarding dynamic range range for LCR and Ls/Rs/LFE channels. They must also have specific requirements regarding bit-depth and sample rate. If you have doubts about this or don’t understand a thing I just wrote, hiring an audio post house really is the best option.

Aren’t format switches fun?

JC Boulay
Audio Z
Montreal, Canada
http://www.audioz.com

[Delano Bryant]

ok, Thanks. We will use Logic Pro to sweeten for a stereo mix. Untill we move our programming to another carrier, then we’ll go 5.1. So, that being said, is Logic Pro better to use for sweeting over Sound Track Pro?