1300023 - Support audio 5.1 on Linux

Status: RESOLVED FIXED

(Core :: Audio/Video: cubeb, task, P2)

Description

[C.M.Chang[:chunmin]]

As title.

Comment 2

[C.M.Chang[:chunmin]]

Attachment: [WIP] Convert layout to channel map

TO-DO: downmix/upmix in pulseAudio

Comment 3

[C.M.Chang[:chunmin]]

Attachment: [WIP] Multi-channel support on Linux

Comment 4

[C.M.Chang[:chunmin]]

The mixing mechanism will be added into cubeb after implementing multiple channel support(bug 1318628).

However, PulseAudio, which is the underlying audio library for cubeb linux, already has a mixing mechanism[0]. Thus, we could set a mixing policy to combine our own mixing module with PulseAudio's mixing mechanism. 

It will be clearer about the mixing policy after investigating the mixing supports on more backends.

[0] https://github.com/ChunMinChang/pulseaudio/blob/1d5dfccbb2b72abca6989a1c85b92e3e6e23bded/src/pulsecore/resampler.c#L841-L900

Comment 5

[C.M.Chang[:chunmin]]

Attachment: Multi-channel support on Linux

Comment 6

[C.M.Chang[:chunmin]]

(In reply to Chun-Min Chang[:chunmin] from comment #4)
> PulseAudio already has a mixing mechanism[0]. 
> [0] https://github.com/ChunMinChang/pulseaudio/blob/1d5dfccbb2b72abca6989a1c85b92e3e6e23bded/src/pulsecore/resampler.c#L841-L900

If we want to downmix 5.1 to stereo when audio file with 3F2-LFE layout with 6 channels, we need to hook the pulseaudio to set channels and layout to 2 and stereo. And then we need to downmix the audio buffer before passing them to the |pa_stream_write| like [0].
[0] https://github.com/ChunMinChang/cubeb/commit/939ad9fb5cb7c11fa0a17d8cd4b3a18efa9fc519

I think this is too hacky. The downmix behaviour is a minor feature, so I think we could open a follow-up bug to discuss this and land the basic support for multi-channel first.

Comment 7

[C.M.Chang[:chunmin]]

Attachment: Multi-channel support on Linux

Hi kinetik,
Could you review this patch? Thanks!

Comment 8

[C.M.Chang[:chunmin]]

merged in https://github.com/kinetiknz/cubeb/pull/207