[Vorbis-dev] 5.1 surround channel coupling

[Richard Lee]

>You misunderstand my post.

>The patch that I'm referring to allows you to take a set of 5.1 --
zillion.1 speaker feeds as input, specify a speaker layout, then it
uses an ambisonic panner to produce an ambisonic rendition of these
feeds for encoding.

Sorry Gregory.  I hope the post was useful anyway.

To answer your real question.  Dolby Digital EX and DTS ES are 7.1 systems.  

I'm not sure how many films have 7.1 soundtracks.  Anyone know?

The bitstream or file may have a channel mask which if Windoz, is likely to be the same as the WAVE_X   dwChannelMask  So the encoder could tell what were the input speaker assignments.

http://dolby.com/consumer/home_entertainment/roomlayout.html

shows 7.1 has the extra speakers at +-150

>> Yes.  Good multichannel "lossless coupling" is essential.  It is this which gives DD a 2:1 advantage over DTS and allows MLP to meet the DVD-A bitrate spec.

>Well, a '2:1 advantage' over anything involves alot of presuppositions
that involve getting some addiitonal ducks in a row for the lossless
coupling.  .

My information is from Eric who is a High Priest of Dolby Digital and also involved with the specification of DVD-A, but I believe these are facts.

a)	Firstly ALL the formal listening tests have been at very low bitrates.  Basically you lower the bitrate until you can hear a difference from the original then that bitrate is your measure of efficiency

b)	On these tests which were conducted by the EBU though Dolby was heavily involved, Dolby Digital shows about 2:1 advantage over DTS on most films.

c)	Encoders evolve.  So DD today is MUCH better than 5 yrs ago and you can see the same trend in eg MP3 and Vorbis.

d)	At the bitrates used for DVD-V sound, Eric challenges anyone to tell the original from either DD or DTS; both are more than good enough .

e)	Films often have little correlation between the fronts & backs and centre dialogue is often quite independent.

e)	Ambisonics which has large inter-channel correlations performs even better cos good multi-channel "lossless coupling"

>I'd like to see Ambisonic be _the_ way to do surround, and if you want 5.1, you get to map it to/from Ambisonic representation

The Ambisonic faithful grovel at your feet oh Guru Monty  ...  8>D



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