822952 - Avoid UpdateReadyState event queue traffic when the next frame status has not changed

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[Matthew Gregan [:kinetik]]

While in the debugger I noticed a large number of calls to nsHTMLMediaElement::ChangeReadyState via UpdateReadyStateForData hitting the early-exit path because the ready state was not changing.  MediaDecoderStateMachine::UpdateReadyState is called from multiple places and dispatches an event each time, even if the state is unchanged.  This can result in many events being created and dispatched during a single video frame.

With a simple current == last status early-exit path added to MediaDecoderStateMachine::UpdateReadyState, the number of events created and dispatched for a simple play-through of a 5 minute video drops from ~140,000 (~468/s or ~15/frame) to 3.

Comment 1

[Matthew Gregan [:kinetik]]

Attachment: patch v0

Tests pass locally.  Try push: https://tbpl.mozilla.org/?tree=Try&rev=9c79c64b62d2

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Comment on attachment 693745 [details] [diff] [review]
patch v0

Review of attachment 693745 [details] [diff] [review]:
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Good catch

Comment 3

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/5f697a87ec46

Comment 4

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/5f697a87ec46