Bug 191419 – [MSE][GStreamer] Soundcloud serves MP4 audio with empty tfdt boxes

• Component: WebKitGTK
• Status: RESOLVED FIXED

[Alicia Boya García]

Soundcloud is currently not working on WebKitGTK, stalling after a few seconds. See for instance:

https://soundcloud.com/ujico/cappuccino

After a little analysis I found it uses MSE with MP4 audio, but its fragments have all their tfdt's set to zero, which is *super wrong*. This means that it appends audio fragments without telling the browser what part of the timeline they pertain.

But that bears the question, how does it manage to work in other platforms? It works in Chrome and Firefox.

I suspect other browsers may be repairing the file by assuming every fragment has the same duration in cases and multiplying it by the sequence number. This problem can be detected safely because when it is present (tfdt == 0 && sequence_number > 0).

[Xabier Rodríguez Calvar]

Eric, Jer, is this working for you? Why?

[Michael Catanzaro]

Ping.

[Alicia Boya García]

The workaround would likely be in the demuxer, not in WebKit code.

[Jer Noble]

That site is currently serving Safari .mp3s, not mp4s:

> [Debug] MediaSource::addSourceBuffer(B9E70A31) audio/mpeg

That could explain why it's working for Mac ports.

[Michael Catanzaro]

I suggest trying a Mac user agent quirk, then.

[Alexander Vereeken]

I found out that soundcloud plays fine by edit the sting /org/gnome/epiphany/web/user-agent with dconf-editor to "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36"

[Alexander Vereeken]

Okay "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:64.0) Gecko/20100101 Firefox/64.0" Seems to be a better workaround because the other one breaks youtube somehow with epiphany.

[Philippe Normand]

Created attachment 431772 [details]
Patch

[EWS]

Committed r279039 (238959@main): <https://commits.webkit.org/238959@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 431772 [details].