I was just wondering...what "format" is your average movie theater soundtrack? How many discrete channels and at what level of compression? Any links to this sort of information would be interesting to me.

You might find this discussion (http://www.dolby.com/assets/pdf/tech_library/4_Multichannel_Music_Mixing.pdf) or this one (http://entertainment.howstuffworks.com/movie-sound6.htm) interesting ... at least as a place to start. ;)

Dolby Digital tracks are recorded on the film itself at a 320 kbps bitrate.

DTS tracks are put on a companion CD that runs in sync with the film and are encoded at a 1.1 mbps rate.

DD uses rates up to 448 on DVD and 640 on Blu-ray.

DTS uses 768 on DVD and 1509 on Blu-ray.

Here's a link to another article (http://www.practical-home-theater-guide.com/dolby-vs-dts.html) which compares DD and DTS, including their theatrical implementations.

Movies are usually done in 5.1 with some specialty configurations such as Imax with added high front speakers to create vertical space. Theaters, of course, have more than a single surround speaker on each side.

There is also SDDS, although I think it's dying off. It never did have the market penetration of the other two.

So when the sound engineer does the mix for the movie does he do it with only 5 channels? I mean if the HD audio formats are doing 7.1 are they mixing in 7.1 and then downmixing for the theater?

I mean if the HD audio formats are doing 7.1 are they mixing in 7.1 and then downmixing for the theater?No. The 5.1-channel theatrical mixes are delivered to the studios that will mixing the home 7.1 version as separate dialogue, effects and music stems. This way, sound effects can be split into side and rear components without the music having to be spread the same way.

Sanjay

No. The 5.1-channel theatrical mixes are delivered to the studios that will mixing the home 7.1 version as separate dialogue, effects and music stems. This way, sound effects can be split into side and rear components without the music having to be spread the same way.

Sanjay

Actually, the mix is usually delivered as 5.1 and the 7.1 is just matrixed out of it. If the studio does not do the mixing itself and contracts out, delivery contracts vary based on the distribution plans of the studio but the typical delivery is
1. a discrete, full bandwidth 5.1 master mix
2. a DM&E which stands for dialog, music and effects on separate tracks (usually used for making foreign versions, not for 7.1)
3. possibly an encoded version, but this is usually done in mastering later

From this, the studio can make anything they want without having to pay to pay for expensive mixing stage time. The original mixed tracks (pre stems) are usually owned by the mixing stage (not the rights, just the mix) that way they can earn extra revenues if the studio wants to make changes later.

Actually, the mix is usually delivered as 5.1 and the 7.1 is just matrixed out of it.Didn't I just say that? a DM&E which stands for dialog, music and effects on separate tracks (usually used for making foreign versions, not for 7.1)In this case the separate stems are being used for making 7.1. Check with Mi Casa Multimedia and Pacific Ocean Post, who are doing the 7.1 mixes for New Line and Lionsgate. They won't do the 7.1 version from a completed 5.1 mix, only from separated dialogue, music and effects.

Sanjay

what if the theater has a digital satellite download of the movie (like Warren THeater here in Oklahoma)?

Actually, 6.1 is fairly common these days, although the rear is usually delivered matrixed into the two rear surround channels, and extracted in the theater if it's DD EX equipped. That's why 6.1 is sufficient for a home theater.