1853057 - Remove `DecodeSupport::Unsupported`

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, task, P1)

Description

[Alastor Wu [:alwu]]

Two reasons to remove DecodeSupport::Unsupported

1. If a DecodeSupportSet doesn't set any decode support, then it won't be equal to DecodeSupport::Unsupported

We have many codes to use this pattern, XXX != media::DecodeSupport::Unsupported or XXX == media::DecodeSupport::Unsupported. But this comparison would fail if the DecodeSupportSet is empty.

For example, in MCSInfo::GetDecodeSupportSet(), if there is no support for the codec, that function would return an empty DecodeSupportSet.

An empty DecodeSupportSet is not equal to media::DecodeSupport::Unsupported, so it leads to an incorrect result. DecodeSupportSet{} != media::DecodeSupport::Unsupported will be true, which is not what we expected.

2. Semantic meaning
   Every flag in EnumSet should be able to exist in the same time. But DecodeSupport::Unsupported is exclusive with other attributes. Eg. It doesn't make sense to have both Unsupported and SoftwareDecode flags on in the same time.

Comment 1

[Alastor Wu [:alwu]]

Attachment: Bug 1853057 - remove DecodeSupport::Unsupport.

See more details in Bug 1853057 comment0.

Comment 2

[Alastor Wu [:alwu]]

Attachment: Bug 1853057 - use the cached remote result to anwser the support information.

When asking config in the content process, we should return result based
on the cached result in the remote decoder because we don't want
to run Windows Media Foundation (WMF) in the content process, which
should be better to run only in the higher security sandboxed process.

We use that function in [1] in the content process to indentify what
types the media engine supports.

[1] https://searchfox.org/mozilla-central/rev/b6cd901cf074c5e75e3902d660bafa3cf3967c40/dom/media/ExternalEngineStateMachine.cpp#332-337

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/34cf458aac56
remove DecodeSupport::Unsupport. r=azebrowski
https://hg.mozilla.org/integration/autoland/rev/064771e8ad7a
use the cached remote result to anwser the support information. r=jolin

Comment 4

[Cosmin Sabou [:CosminS]]

Backed out for causing mda failures on test_video_low_power_telemetry.html

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&selectedTaskRun=eju6r6dmSISl1OVFxvFxvQ.0&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=064771e8ad7a3103773e4672793df92df9c1199c

Failure log: https://treeherder.mozilla.org/logviewer?job_id=429230657&repo=autoland

Backout link: https://hg.mozilla.org/integration/autoland/rev/6f38538b7fef8e69ab8bd61c9a9c6afb7890c324

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ebd79534e63f
remove DecodeSupport::Unsupport. r=azebrowski
https://hg.mozilla.org/integration/autoland/rev/2ed0045b3cbf
use the cached remote result to anwser the support information. r=jolin

Comment 6

[Cosmin Sabou [:CosminS]]

Relanded this because it turned out to be from Bug 1852806.

Comment 7

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/ebd79534e63f
https://hg.mozilla.org/mozilla-central/rev/2ed0045b3cbf