1451747 - [webvtt] Subtitles can be placed outside the video

Status: RESOLVED DUPLICATE of bug 1305732

(Core :: Audio/Video: Playback, defect, P3)

Description

[Dennis Schubert [:denschub]]

Attachment: Screenshot showing differences in subtitle placement in Chrome and Firefox

With cue settings like `align:end position:90%`, it is possible to place subtitles outside the <video> element.

I created a little test case at http://stuff.schub.io/mozilla/testcases/webc-16192/, but it's rather simple:

- From second 3 to second 6, a subtitle with `align:start position:10%` is shown, causing it to be placed off to the left, outside the video.
- From second 6 to second 9, a subtitle with `align:end position:90%` is shown, and thus, it is visible on the right, also outside the video.

While those placement information may be questionable, Chrome handles them just fine. I attached a screenshot for illustration.

This was created out of a bug report we received about YouTube. I'm adding webcompat? here, just for reference, but ... I don't think this happens frequently, especially since YouTube officially has no UI for placing the subtitles differently.

Comment 1

[Jan Henning [:JanH]]

Attachment: youtube-subtitles.png

(In reply to Dennis Schubert [:denschub] from comment #0)
> This was created out of a bug report we received about YouTube. I'm adding
> webcompat? here, just for reference, but ... I don't think this happens
> frequently, especially since YouTube officially has no UI for placing the
> subtitles differently.

Actually this is happening even with subtitles that are described as being "(Automatic Captions)", and since in Firefox for Android Youtube is apparently relying fully on the browser's subtitle handling, this would change the assumptions about how frequently this is happening somewhat.

Can I ask to reconsider the priority in view of this?

Comment 3

[Jan Henning [:JanH]]

(see comment #1).

Comment 4

[Dennis Schubert [:denschub]]

Ah, thanks for the ping, but I am not responsible for any priorities for the A/V team. :) Redirecting to Nils.

I have not yet seen automatic captions break, but I also didn't watch too many videos with subtitles for testing, so this may be a possibility. If that's the case, then yeah, that is more serious.

Comment 6

[Alastor Wu [:alwu]]

I'm starting looking at bug1488673 which also relates with this issue, so maybe the solution can fix both of these bugs.

Comment 7

[Alastor Wu [:alwu]]

This issue will be fixed in bug1488673, I will close this bug once the fix has been verified on Nightly.

Comment 8

[Alastor Wu [:alwu]]

Bug 1488673 fixed part of this issue, but it didn't fix all cases. This issue will be fixed completely in bug1305732.