1951071 - Testcase generating N VTTs is 3222x slower for N=500 and infinitely slower for N=5000

Status: RESOLVED WONTFIX

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

Description

[Mayank Bansal]

Attachment: VTT.html

Open attached testcase
Enter 500 (5000 if you are brave)

N=500
Nightly: https://share.firefox.dev/4ifhN1J (29s)
Chrome: https://share.firefox.dev/3QC9sJx (9ms)

N=5000
Nightly: iloop. I think i waited for maybe 10 minutes before quitting.
Chrome: https://share.firefox.dev/3FaSvU3 (174ms)

Testcase created by ChatgPT on my prompt. Very unrealistic, but maybe it highlights some hotspots?

Comment 1

[Mayank Bansal]

Attachment: about:support

Comment 2

[Mayank Bansal]

Incomplete 3.35 minute long profile for N=5000: https://share.firefox.dev/4h1hFC6

Comment 3

[Mayank Bansal]

If you comment out this line, the testcase is very fast

video.appendChild(track);

Comment 4

[Paul Adenot (:padenot)]

Yeah that's true, but I don't think you'd add 500 subtitle tracks to your video so that's not much of a priority.

Comment 5

[Mayank Bansal]

Thanks Paul. I will close as WONTFIX. Plenty other more realistic bugs exist.

Comment 6

[Mayank Bansal]

This still repros: https://share.firefox.dev/40P8rDJ