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[mediacapture-main] Add a channel count constraint to spec

From: Harald Alvestrand via GitHub <sysbot+gh@w3.org>
Date: Fri, 19 Jun 2015 08:17:26 +0000
To: public-media-capture-logs@w3.org
Message-ID: <issues.opened-89502805-1434701845-sysbot+gh@w3.org>
alvestrand has just created a new issue for 
https://github.com/w3c/mediacapture-main:

== Add a channel count constraint to spec ==
Proposal from Joe Berkovitz on behalf of the Audio WG.

Summary:

The proposed change will associate a channel count with an audio 
MediaTrack, allowing both device discovery (via constraints) and 
device description (via capabilities and settings) to account for the 
number of audio channels in a track.

Rationale:

Channel counts are fundamental descriptors of audio tracks, as width 
or height are fundamental to video tracks (for input, at any rate). 
Knowing the potential and real channel counts of device streams are 
essential for audio-based apps to present or make meaningful choices 
between devices, and to adjust an application's behavior to best fit a
 given device.

The Audio WG did consider using an enumerated type for channel layouts
 (e.g. "mono", "5.1", etc.) but has settled on channel counts because 
they are always knowable and discoverable in the UA's native 
environment, while knowledge of actual channel layouts are neither 
universally available nor standardized. Channel layout constraints 
could be added in the future if needed.

Definitions:

The channel count of an audio track is the number of independent 
channels of sound that it contains, i.e. the number of audio samples 
per sample frame.

Proposed changes:

- Add a boolean channelCount attribute to 
MediaTrackSupportedConstraints.
- Add a long channelCount attribute to MediaTrackSettings
- Add a long/LongRange channelCount attribute to 
MediaTrackCapabilities
- Add a ConstraintLong channelCount attribute to 
MediaTrackConstraintSet

Thank you very much for your consideration.

See https://github.com/w3c/mediacapture-main/issues/197
Received on Friday, 19 June 2015 08:17:30 UTC

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