1238462 - [emulator-x86-kk][mochitest] TEST-UNEXPECTED-FAIL | dom/media/test/test_playback.html | small-shot.m4a duration (NaN) should be around 0.29

Status: RESOLVED WONTFIX

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

Description

[Hsin-Yi Tsai (she/her) [:hsinyi]]

log https://treeherder.mozilla.org/logviewer.html#?job_id=3719222&repo=b2g-inbound

mochitest chunk 30 https://treeherder.mozilla.org/#/jobs?repo=b2g-inbound&revision=048b60ee7fdd&exclusion_profile=false&selectedJob=3719222

Comment 1

[Benjamin Chen [:bechen]]

The small-shot.m4a duration is assigned |MediaDecoderStateMachine::OnMetadataRead|, then send metadataload event to main thread.

I suspect there is a racing between "set mDuration" and "MediaDecoderStateMachine::EnqueueLoadedMetadataEvent".

1. The "set mDuration" is a Canonical, so it will dispatch a task(DoNotify) to self then dispatch to main thread.

2. "MediaDecoderStateMachine::EnqueueLoadedMetadataEvent" seems dispatch to main thread directly.


So the "metadataload event" is before than "mirror value update" in main thread. Once the "metadataload event" comes first, the HtmlMediaElement fires the async event "loadedmetadata" to js get the NaN duration.

JW, how do you think?

Comment 2

[JW Wang [:jwwang] [:jw_wang]]

https://hg.mozilla.org/mozilla-central/file/f59d1f7941b0b7358d6fa28179d60280ac2844b9/dom/media/MediaDecoder.cpp#l745

AbstractThread::MainThread() is assigned as the target thread when MediaDecoder registers a listener with the event source. Tail dispatching should kick when the event is published and sent to the listener.

You can run a debugger to make sure tail dispatching is activated.

Comment 3

[Benjamin Chen [:bechen]]

(In reply to JW Wang [:jwwang] from comment #2)
> https://hg.mozilla.org/mozilla-central/file/
> f59d1f7941b0b7358d6fa28179d60280ac2844b9/dom/media/MediaDecoder.cpp#l745
> 
> AbstractThread::MainThread() is assigned as the target thread when
> MediaDecoder registers a listener with the event source. Tail dispatching
> should kick when the event is published and sent to the listener.
> 
> You can run a debugger to make sure tail dispatching is activated.

https://dxr.mozilla.org/mozilla-central/source/xpcom/threads/StateMirroring.h#195
My point is that since the set function in canonical doesn't dispatch task to mainthread(mirror) directly.
So the loadedmetadata event will run before updateValue? If so, may cause the problem.

Comment 4

[JW Wang [:jwwang] [:jw_wang]]

Direct tasks should run before tail dispatching.

Comment 5

[Anthony Jones (:ajones, :kentuckyfriedtakahe, :k17e)]

Mass change P2 -> P3

Comment 6

[Hsin-Yi Tsai (she/her) [:hsinyi]]

The project was canceled. Marked this as wontfix.