1566203 - When using composition recorder with BrowserTime, too many frames are skipped

Status: NEW

(Core :: Graphics: Layers, defect, P3)

Description

[Chris Liu]

When using the composition recorder to capture screenshots for browsertime, the frames immediately after the orange frame is not picked up until a few hundred milliseconds later. Below is a captured profile using Browsertime and the timestamps for the first few frames captured by the frame recorder.

https://perfht.ml/2XPVXIx

/Users/chliu/browsertime-results/www.cnn.com/2019-07-15T131030-0400/windowrecording-1563210634580.52/frame-1-248.png   
/Users/chliu/browsertime-results/www.cnn.com/2019-07-15T131030-0400/windowrecording-1563210634580.52/frame-2-649.png    
/Users/chliu/browsertime-results/www.cnn.com/2019-07-15T131030-0400/windowrecording-1563210634580.52/frame-3-1301.png   
/Users/chliu/browsertime-results/www.cnn.com/2019-07-15T131030-0400/windowrecording-1563210634580.52/frame-4-1747.png

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Chris, are you planning on investigating why this is happening?

Comment 2

[Markus Stange [:mstange]]

Some more information here:

In the profile, if you go to the marker chart view and hover the CompositorScreenshot marker for the orange frame, the tooltip shows you that the marker's duration is 67ms. In other words, the orange frame was on the screen for 67ms and was then replaced by a new screenshot which was no longer orange.

In the files captured by the frame recorder, the orange frame is frame-2-649.png. The next captured frame is frame-3-1301.png. This means that the frame recorder "thought" the screen stayed orange for 1301 - 649 = 652 milliseconds, which is 585 milliseconds too long.
So something is causing the screen to go from orange to non-orange in a way that the compositor does not detect as a "content change".

Comment 3

[Timothy Nikkel (:tnikkel)]

Might be the same underlying issue as bug 1565225. Flip the pref layout.display-list.retain.chrome to false to see if the problem goes away.

Comment 4

[Chris Liu]

(In reply to Timothy Nikkel (:tnikkel) from comment #3)

Might be the same underlying issue as bug 1565225. Flip the pref layout.display-list.retain.chrome to false to see if the problem goes away.

Unfortunately, this fix doesn't seem to work for me

Comment 5

[Chris Liu]

(In reply to Jeff Muizelaar [:jrmuizel] from comment #1)

Chris, are you planning on investigating why this is happening?

Hi Jeff, I am not planning to do deeper investigation at the moment.