Bug 235592 - [Cocoa] rVFC() callbacks have up to 60ms extra latency
Summary: [Cocoa] rVFC() callbacks have up to 60ms extra latency
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: Media (show other bugs)
Version: WebKit Nightly Build
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Jer Noble
URL:
Keywords: InRadar
Depends on:
Blocks:
 
Reported: 2022-01-25 08:59 PST by Jer Noble
Modified: 2022-01-31 11:59 PST (History)
7 users (show)

See Also:

Attachments
Patch (53.89 KB, patch)
2022-01-25 09:17 PST, Jer Noble 		dino: review+
Details | Formatted Diff | Diff
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Description Jer Noble 2022-01-25 08:59:01 PST 
[Cocoa] rVFC() callbacks have up to 16ms extra latency
Comment 1 Radar WebKit Bug Importer 2022-01-25 09:15:47 PST 
<rdar://problem/88027149>
Comment 2 Jer Noble 2022-01-25 09:15:57 PST 
Correction: 60ms extra latency.
Comment 3 Jer Noble 2022-01-25 09:17:51 PST 
Created attachment 449934 [details]
Patch
Comment 4 Jer Noble 2022-01-26 13:52:55 PST 
Unfortunately, Performance testing shows this patch to have a negligible effect on latency. It appears latency is more greatly determined by when in a display refresh cycle the frame becomes available.  The good news is that even without this patch, frame display latencies are in the order of 9-16ms.
Comment 5 Maciej Stachowiak 2022-01-31 10:43:15 PST 
Is it 60ms or 9-16ms? The former seems fatal to use of the feature, the latter seems maybe ok?
Comment 6 Jer Noble 2022-01-31 11:59:42 PST 
(In reply to Maciej Stachowiak from comment #5)
> Is it 60ms or 9-16ms? The former seems fatal to use of the feature, the
> latter seems maybe ok?

Potentially 60ms, because that's the timer which AVPlayerItemVideoOutput uses to purge samples. In practice, I've never seen it higher than 16ms on this particular machine.