5.1 DVD Audio Formats

Question

Making DVDs : When a dvd is made. Is it true that they usually put it in this order : 1.L - 2.R - 3.C - 4.LFE - 5.Ls - 6.Rs - 7.Lt - 8.Rt - and when the dvd is read and a 5.1 audio system is detected it will play channels 1-6, and if a 5.1 audio system isn't detected it plays 7-8? (with dialnorm ensuring the volume is the same).

If the answer is "yes", then where exactly do AC3's fit in, and when are they most often used? Digital distribution like itunes and netflix? I like the idea that you can tailor the stereo mix, to make the film sound optimal in stereo, but you can't do that with an AC3 (since it folds down itself, according to how you encode it).

Thanks!!!!

Answer 1

Yes and no. The order is: L - R - C - LFE - LR - RR alright, but the LT and RT is for format mastering purposes only (not to be confused with the pre-mastering normally just called mastering in music), and not used in the actual 5.1-track at all. It is, however, used for the stereo-track and other similar applications.

The AC3/DTS/etc. coding comes after this, and the tracks are encoded separately in the same way as for example DD, DTS, PCM and so on can't be combined under one file. Myself, I never use the total-track when watch DVD's in stereo though. I normally think the players mixdown-function does a better job for some reason. Not really sure why, but t might be that the stereo-track might be more heavily encoded as the producers expect people who minds the difference to prefer surround anyway. Yet again, this last part is just me speculating, I never encode my mixes myself, it's not my work to do and would be too risky in respect to the movie in terms of sync and such in whole. Though we must know how things are treated, this step is always up to the DVD-mastering-dudes and dudettes.

Answer 2

DVD's don't have a track order in the way your thinking about it. The common workflow would be to have the exported multiple mono files and you tell the encoding software which file is for which channel. These are then encoded into an AC3. AC3 has it's own built in fold down or you can put an LT/RT or a stereo mix, PL2 encoded file etc. as long as it's an audio format supported by the DVD spec - on a secondary track on the DVD.