User:Jeff Kelley/Multichannel Audio

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Introduction

Since QuickTime 7, it is possible to deliver multichannel audio. Second Life streamed audio relies on QuickTime and inherits this capability without further work.

Producing a multichannel audio movie

We are using ProTools. Export a multichannel track (ou bounce a multichannel master fader) to multimono files. Here is an example with a 5.1 (L C R Ls Rs Lf) track and the six mono files you get.

In QuickTime Pro, create a new movie then import the six mono files. You have to open each of the six tracks, select all, "Add to Movie" with playhead at start. Tedious, but we will come with a better solution soon. Now, "Show Movie Properties" then "Audio Settings".

Assign carefully each track. Note that you can see the original filenames in the "Resources" tab.

Mapping between QuickTime and industry-standard labeling

Left	L
Right	R
Center	C
LFE Screen	LFE
Left Surround	Ls
Right Surround	Rs
Left Center	Lc
Right Center	Rc
Center Surround	Cs
Rear Surround Left	Lr
Rear Surround Right	Rr

Once tracks assigned, choose File>Export, Movie to QuickTime Movie, Options, Sound Settings, Channels. Wow!

Note that the compression format used will limit the choice of surround formats available. You will most probably prefer AAC over PCM, and the AAC 5.1 format is C L R Ls Rs LFE. However, industry-standard is L C R Ls Rs LFE. Be careful here. Confused? Here is a table to help:

Multichannel Mixing and Surround Formats

Format	Channels	Layout
Mono	1	C
Stereo	2	L R
Cinema Stereo	3	L C R
Quadraphonic	4	L R Lr Rr
Dolby ProLogic	4	L C R S
Film (Dolby Digital)	6	L C R Ls Rs LFE
SMPTE/ITU	6	L R C LFE Ls Rs
DTS	6	L R Ls Rs C LFE
Dolby Surround EX	7	L C R Ls Cs Rs LFE
SDDS	8	L Lc C Rc R Ls Rs LFE

NOTE: delete Image:Jef Kelley Images QT Audio Tracks Assign.png (stupid one)