1524026 - Web audio didn't produce sound even if AudioContext is resumed from blocked

Status: RESOLVED FIXED

(Core :: Web Audio, defect, P2)

Description

[Alastor Wu [:alwu]]

Attachment: Debug Log (Autoplay:5,WebAudioAPI:5)

Fork from bug1511117 comment1, after clicking a keyborad key, the site would call OscillatorNode.start() which would resume the AudioContext [1].

However, even the AudioContext has been resumed, I still can't hear any sound from web audio.

[1] https://searchfox.org/mozilla-central/rev/78cd247b5d7a08832f87d786541d3e2204842e8e/dom/media/webaudio/OscillatorNode.cpp#491

Comment 1

[Alastor Wu [:alwu]]

Hi, Paul,
Could you help me take a look for this issue?
Thank you!

Comment 2

[Alastor Wu [:alwu]]

Have found the root cause, will upload a patch and update my analysis later.

Comment 3

[Alastor Wu [:alwu]]

The root cause is that there was a stream which wasn't resumed by the AudioContext because that stream was not belong to a Node, which resulted that AudioContext can't get it when calling GetAllStreams().

The stream is created by the AudioParam [1]. Therefore, this stream blocks other streams which were connected to the GainNode, which resulted that AudioContext didn't output any sound.

[1] https://searchfox.org/mozilla-central/rev/6e3cc153566f5f288ae768a2172385b8436d61dd/dom/media/webaudio/AudioParam.cpp#81

Comment 4

[Alastor Wu [:alwu]]

Attachment: Bug 1524026 - part1 : to allow 'AudioContext::GetAllStreams()' to get helper streams.

If the stream has not current AudioNode which means it's not controlled by AudioContext (like MediaRecorder's and AudioParam's stream) so their suspended count don't need to be adjusted by asking AudioContext. Therefore, we only change stream's suspended count when its node exists.

If we don't do so, the stream would have incorrect suspended count because AudioContext won't control the stream and have no way to resume it.

Comment 5

[Alastor Wu [:alwu]]

Attachment: Bug 1524026 - part 2 : add test.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0f0f272b39ac
part1 : to allow 'AudioContext::GetAllStreams()' to get helper streams. r=padenot
https://hg.mozilla.org/integration/autoland/rev/986f3ebb901a
part 2 : add test. r=padenot,smaug

Comment 7

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/0f0f272b39ac
https://hg.mozilla.org/mozilla-central/rev/986f3ebb901a