Bug 240549

Summary:	Duplicated cues of in-manifest captions, if cue properties modified
Product:	WebKit	Reporter:	Gary Katsevman <webkit>
Component:	Media	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	eric.carlson, jer.noble, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	Safari Technology Preview
Hardware:	All
OS:	All

Description Gary Katsevman 2022-05-17 16:14:19 PDT

If, when, playing back an HLS stream with in-manifest captions, a cue's properties are modified, when seeking back and replaying the video so that the cue becomes active again, the cue becomes duplicated.
Modifying any property of the cue will cause a new cue to be re-added with the original values and both of them to be displayed.

I have a live example here https://simple-video.netlify.app/double-cues.html
It waits for some cues to be available, modifies their `line` properties to be `0` and then seeks back. On the second play, there are now cues at the top and the bottom of the display area.

To me, this seems a bit unexpected that a new cue is created even though the original reference still exists, even if it was modified.
I'd expect no new cues to be created.

Comment 1 Radar WebKit Bug Importer 2022-05-19 19:51:30 PDT

<rdar://problem/93624739>