[webkit-gtk] Question about Media Source Extension

Cédric Bellegarde cedric.bellegarde at adishatz.org
Wed Feb 28 05:54:03 PST 2018

Finally got it: https://bugs.webkit.org/show_bug.cgi?id=183211


Le mer. 28 févr. 2018 à 14:31, =?iso-8859-1?q?C=E9dric?= Bellegarde 
<"cedric.bellegarde"@adishatz.org> a écrit :
> My bad, after reading Philippe comment, I was searching how the hell 
> was this possible. And after testing with epiphany, it was more: "how 
> the hell is this possible in Eolie?".
> And the bug was in Eolie, one line was setting it off and later 
> another one was setting it on... Sorry for the noise.
> BTW, I will let it on in Eolie as this may allow you to get more 
> backtrace.
> I'm trying to reproduce one crash for now with: full bt + gstreamer 
> debug files.
> regards,
> Le mer. 28 févr. 2018 à 14:24, Michael Catanzaro 
> <mcatanzaro at igalia.com> a écrit :
>> On Wed, Feb 28, 2018 at 1:20 AM, Cédric Bellegarde 
>> <cedric.bellegarde at adishatz.org> wrote:
>>> And here my surprise, with -DENABLE_MEDIA_SOURCE=ON and 
>>> enable-mediasource=False, 1080p is available in YouTube and 
>>> WebKitGTK does not crash anymore.
>> WOW! This is a major discovery.
>> The good news is that you must have been testing our stable release 
>> rather than  our latest development release, WebKitGTK+ 2.19.91, 
>> where we actually have enabled the ENABLE_MEDIA_SOURCE=ON build 
>> option. It's still off by default at runtime, because it does not 
>> work reliably yet, but that is exactly the configuration that you've 
>> requested.
>> It seems quite bad that enabling the build option but not the 
>> runtime option enables higher-resolution video playback on YouTube, 
>> though, because that means that the feature is somehow web-exposed 
>> such that YouTube can detect it, even though it is supposed to be 
>> disabled at runtime. That seems like a major bug. It indicates that 
>> the runtime option does not function properly in some way or 
>> another, and that leaving the build option enabled is risky, and 
>> that we should reevaluate our choice to enable the build option. 
>> This is somewhat urgent, because we have a new stable release coming 
>> up in a week and a half. Enrique, Alicia, could you investigate this 
>> to see what is wrong, please?
>> In the past, when the MSE feature was originally developed, WebKit 
>> did not support hiding JavaScript features at runtime. That's no 
>> longer the case -- nowadays, we would expect the MSE features to be 
>> completely invisible to webpages when the runtime option is disabled 
>> -- but perhaps that was never properly implemented for MSE. (That is 
>> actually the reason why we have started using more runtime options 
>> in WebKit, in preference to build options.) Anyway, I don't know how 
>> to fix this; it requires some investigation.
>> Michael
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