1300455 - [meta] Multiple channel support on playback

Status: NEW

(Core :: Audio/Video: Playback, enhancement, P3)

Description

[C.M.Chang[:chunmin]]

This is a meta bug for audio 5.1 support on playback

Comment 1

[C.M.Chang[:chunmin]]

The Gecko's AudioConverter downmix the audio data which has more than two channels into stereo or mono[0] before passing it to cubeb. The reason to do that is because cubeb has no multi-channel support. Once cubeb implements multi-channel support and mixing mechanism, there is no need to downmix first in gecko.

We should move the downmix mechanism from gecko into cubeb one by one on each platform. If we implement the multi-channel support on Windows, then we should disallow the downmix mechanism in gecko on Windows and let cubeb to do that job. The downmix in gecko will be removed until the multi-channel support is implemented on each backend. 

[0] http://searchfox.org/mozilla-central/rev/d98418da69edeb1f2f8e6f3840157fae1512f89b/dom/media/AudioConverter.cpp#160-216

Comment 2

[C.M.Chang[:chunmin]]

To keep the stability, we should bypass the AudioConverter's downmix/upmix on Windows first and keep intact on other platforms. This can narrow down the effects when the bugs come but give us necessary information to revise. Once it's stable, we could apply this feature to other backends.

I'll open another bug to track this issue.

Comment 3

[C.M.Chang[:chunmin]]

The overview of multiple channel support is updated here: https://wiki.mozilla.org/Media/multichannel