1149852 - Firefox does not display subtitles/captions as expected

Status: RESOLVED DUPLICATE of bug 1281418

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

Description

[Guru Prasad]

Attachment: test.html

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0
Build ID: 20150320202338

Steps to reproduce:

Created a page with:
<video id="video" ...>
  <source id="mp4" ...>
  <track id="sub" ...>
</video>

Created a new video, source and track element via javascript.
Ran 
video.parentNode.replaceChild(new_video, video);
new_video.load()




Actual results:

The video loaded fine, but there was no GET request issued for the track.

Upon stepping through the javascript using the firefox javascript debugger(not sure of the technical name), a GET request was issued for the track.


Expected results:

A GET request should have been issued for the track element.

Comment 1

[Guru Prasad]

The attachment contains sample code that loads a video and track. Please note that the track does not correspond to the video.

Comment 2

[Guru Prasad]

Is there anything else I can do to help resolve this bug?
I'm not too familiar with the source code layout, however, if you can give me some pointers on where to start debugging, I could take a stab at it.

Comment 3

[Anthony Jones (:ajones, :kentuckyfriedtakahe, :k17e)]

I don't understand the bug report. Why does the GET request matter?

Comment 4

[Guru Prasad]

The GET request matters if you want to obtain the track element along with the video. Without this GET request, we don't have access to subtitles/vtt elements.

Comment 5

[Anthony Jones (:ajones, :kentuckyfriedtakahe, :k17e)]

(In reply to Guru Prasad from comment #4)
> The GET request matters if you want to obtain the track element along with
> the video. Without this GET request, we don't have access to subtitles/vtt
> elements.

Are you saying that the symptom is subtitles/vtt not working and the lack of the GET request appears to be the cause?

Comment 6

[Guru Prasad]

Yes, the symptom is the lack of subtitles and the cause is that no GET request was being generated for the track element.

Comment 7

[Guru Prasad]

Maybe I'm not communicating this right.
I had attached a file (test.html) with the initial bug report.

If you were to open this file with Google Chrome, you would see that it plays a video and also displays subtitles/captions. However, if you open it with Firefox, the subtitles/captions never show.

Looking at the developer console's network activity, you will notice that there was no GET request issued for the track element. 

On a slightly unrelated note, if you enable console debugging and put a break point and step through the debugger, you will see that it actually does send out a request and then shows subtitles/captions.

So my point is:
  a) Firefox does not display subtitles/captions as expected
  b) Firefox is not issuing GET requests for track elements
  c) Firefox's behaves differently while using the debugger