Difference between revisions of "User:Jeff Kelley/Multichannel Audio"

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&nbsp;&nbsp;&nbsp;'''WORK IN PROGRESS'''
&nbsp;&nbsp;&nbsp;'''WORK IN PROGRESS'''
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</div>


== Introduction ==
==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.
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 ==
==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.
===Step 1: Produce an interleaved multichannel WAV file===
 
We are using ProTools. Bounce a multichannel session to Stereo interleaved format:


[[Image:PT Multichannel Track.png]]
[[Image:PT Multichannel Track.png]]
[[Image:PT Multimono Files.png]]


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".
===Step 2: Open with QuickTime Pro===
 
Choose menu 'Show Movie Properties', select 'Sound Track', select 'Audio Settings' tab:


[[Image:QT Audio Tracks Assign.png]]
[[Image:QT Audio Tracks Assign.png]]


Assign carefully each track. Note that you can see the original filenames in the "Resources" tab.
===Step 3: Export to QuickTime Movie===
 
Choose 'Export', 'Movie to QuickTime Movie', 'Options', 'Sound Settings', 'Channels'.
 
[[Image:QT_Audio_Tracks_Export.png]]
 
===Step 4: Stream the usual way===
 
Using an HTTP server and Second Life's 'About Land > Media'.
 
 
==Playing multichannel audio==
 
In order to play multichannel audio, we need to link some audio hardware to QuickTime, don't we? On Windows, this is done in the QuickTime Settings control panel. First, select an audio interface (aka "sound card"), then select a mutichannel format.
 
[[Image:QT Audio Tracks Interface Win.jpg]]
 
On the Macintosh, this is done via the Audio Midi Setup utility (not via the Sound control panel as one would expect). Select your multichannel interface in the Properties popup menu. Click Configure Speakers, then Multichannel.
 
[[Image:QT Audio Tracks Interface Mac.png]]
 
Here, we are assigning the 8 analog output channels of our [http://www.digidesign.com/index.cfm?langid=100&navid=31&itemid=4895 DIGI 002] studio interface to a 5.1 surround setup. The speakers setup must match stream content otherwise we would get "sound everywhere in the room" but no spatial location.
 
==QuickTime multichannel audio support==
 
===Channels Assignements===


==== Mapping between QuickTime and industry-standard labeling ====
{|{{Prettytable}}
{|{{Prettytable}}
!
| L
!
! Mono
! Stereo
! Cinema Stereo
! Quadraphonic
! Dolby ProLogic
! Film (Dolby Digital)
! SMPTE/ITU
! DTS
! Dolby Surround EX
! SDDS
|-
| Left
| Left
| L
|
| x
|-  
|-  
| R
| Right
| Right
| R
|
| x
|-
|-
| C
| Center
| Center
| C
| x
|-
|-
| LFE
| LFE Screen
| LFE Screen
| LFE
|-
|-
| Ls
| Left Surround
| Left Surround
| Ls
|-  
|-  
| Rs
| Right Surround
| Right Surround
| Rs
|-  
|-  
| Lc
| Left Center
| Left Center
| Lc
|-  
|-  
| Rc
| Right Center
| Right Center
| Rc
|-
|-
| Cs
| Center Surround
| Center Surround
| Cs
|-  
|-  
| Rls
| Rear Surround Left
| Rear Surround Left
| Lr
|-  
|-  
| Rrs
| Rear Surround Right
| Rear Surround Right
| Rr
|}
 
For a full-reference, see
[http://developer.apple.com/documentation/QuickTime/Conceptual/QT7UpdateGuide/Chapter02/chapter_2_section_6.html QuickTime 7 Audio Enhancements]
 
Note: Core Audio also support the following recording formats: XY Stereo, MS Stereo, WXYZ Ambisonic (B-Format). The latter is especially interesting for immersive 3D with soundfield recordings. Although consumer multichannel audio supports only surround formats, some succes has been achieved matrixing ambisonics to surround. See Robert Miller, AES 2003 http://www.ambiophonics.org/AESJune2003/AES_June_2003_1.htm 
 
==== Multichannel Mixing and Surround Formats ====
 
{|{{Prettytable}}
! 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)
'''NOTE:''' delete [[:Image:Jef Kelley Images QT Audio Tracks Assign.png]] (stupid one)

Latest revision as of 12:14, 3 January 2008

   WORK IN PROGRESS

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

Step 1: Produce an interleaved multichannel WAV file

We are using ProTools. Bounce a multichannel session to Stereo interleaved format:

PT Multichannel Track.png

Step 2: Open with QuickTime Pro

Choose menu 'Show Movie Properties', select 'Sound Track', select 'Audio Settings' tab:

QT Audio Tracks Assign.png

Step 3: Export to QuickTime Movie

Choose 'Export', 'Movie to QuickTime Movie', 'Options', 'Sound Settings', 'Channels'.

QT Audio Tracks Export.png

Step 4: Stream the usual way

Using an HTTP server and Second Life's 'About Land > Media'.


Playing multichannel audio

In order to play multichannel audio, we need to link some audio hardware to QuickTime, don't we? On Windows, this is done in the QuickTime Settings control panel. First, select an audio interface (aka "sound card"), then select a mutichannel format.

QT Audio Tracks Interface Win.jpg

On the Macintosh, this is done via the Audio Midi Setup utility (not via the Sound control panel as one would expect). Select your multichannel interface in the Properties popup menu. Click Configure Speakers, then Multichannel.

QT Audio Tracks Interface Mac.png

Here, we are assigning the 8 analog output channels of our DIGI 002 studio interface to a 5.1 surround setup. The speakers setup must match stream content otherwise we would get "sound everywhere in the room" but no spatial location.

QuickTime multichannel audio support

Channels Assignements

L Left
R Right
C Center
LFE LFE Screen
Ls Left Surround
Rs Right Surround
Lc Left Center
Rc Right Center
Cs Center Surround
Rls Rear Surround Left
Rrs Rear Surround Right

For a full-reference, see QuickTime 7 Audio Enhancements

Note: Core Audio also support the following recording formats: XY Stereo, MS Stereo, WXYZ Ambisonic (B-Format). The latter is especially interesting for immersive 3D with soundfield recordings. Although consumer multichannel audio supports only surround formats, some succes has been achieved matrixing ambisonics to surround. See Robert Miller, AES 2003 http://www.ambiophonics.org/AESJune2003/AES_June_2003_1.htm

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)

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