[webkit-gtk] Question about Media Source Extension

Konstantin Tokarev annulen at yandex.ru
Wed Feb 28 05:28:26 PST 2018

28.02.2018, 16:24, "Michael Catanzaro" <mcatanzaro at igalia.com>:
> 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?

FWIW, in QtWebKit I've seen that html5test.com reports error when MSE
is enabled at build time but disabled at run time, while builds with disabled
MSE didn't expose that behavior

> 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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