AES/EBU Conversion

[weso33]

So I'm finishing up a mix of a film currently, and am getting to the point where I'll be sending mixes to the video guys to be locked to picture for the client to watch / listen etc. In the end, we're making dvds for the client to send to various film festivals etc, so I'm obviously going to be encoding an AC3 of the final mix for those discs. Adjacent to our video finishing rooms, we have a theater set up that works quite well for video playback, and has a really nice high end (but still consumer) surround audio playback system. In the past, with stereo mixes/masters, we send a signal directly out of AVID or FCP into the theater room and the clients are able to view the final products in a great environment. But that's stereo. Since this client wants a 5.1 mix, what we've done in the past is just make dvds and have them view those discs in the theater. That's a bit of a time-suck, as with every version we have to create new discs etc... it's just not very efficient.

So on to my question - is there any reason why I couldn't give the video guys my AC3, have them place it with picture in FCP (I know AVID doesn't accept AC3...which kind of baffles me...), send the AC3 out of FCP via AES/EBU, and use something like a Hosa ODL-312 to convert it to optical and insert it directly into the receiver?

It seems like a stretch to me - yet logically...am I wrong in thinking that might work? If not, what all do you guys do? Obviously it would be nice to be working in a dub stage - and we're working to get to that point, but since we're not there yet, having easy, efficient ways to QC mixes in various environments would be nice. Thanks in advance for the help!

[weso33]

Welp - so I just got some info from Hosa tech support -

"We did some research and the AC3 files will not pass through our converter boxes"

So that's where I'm a little bit hazy then - is this just not something that would work? What's the difference between taking an AC3 out FCP vs taking an AC3 out your standard dvd player? Obviously, as long as the receiver can decode it ... but beyond that, am I just missing something?

[Eric Seaberg]

Originally Posted by weso33

So on to my question - is there any reason why I couldn't give the video guys my AC3, have them place it with picture in FCP (I know AVID doesn't accept AC3...which kind of baffles me...), send the AC3 out of FCP via AES/EBU, and use something like a Hosa ODL-312 to convert it to optical and insert it directly into the receiver?

Avid won't accept AC3 because it's not a 'production' format but a 'delivery' format. For production, you'd use Dolby E which is NOT compatible with AC3.

You can use something like Neyrinck's Dolby Digital plug-in and create the AC3 file, as you thought. You can import it into FCP and play straight out. You may have to make some changes in FCP's prefs as it will, most likely, try to DECODE the AC3 stream and give you a downmix for monitoring on the editor. Remember, too, that Dolby requires a frame of video to decode, so be sure to slip your AC3 file 1-frame ahead of the picture in FCP to keep it in sync.

I think that should work....