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2517: disable Media Capabilities API (for now)
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@Thorin-Oakenpants
Thorin-Oakenpants authored Nov 13, 2018
1 parent 8fd6061 commit f214e4b
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5 changes: 5 additions & 0 deletions user.js
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Expand Up @@ -1214,6 +1214,11 @@ user_pref("dom.webaudio.enabled", false);
/* 2516: disable PointerEvents
* [1] https://developer.mozilla.org/en-US/docs/Web/API/PointerEvent ***/
user_pref("dom.w3c_pointer_events.enabled", false);
/* 2517: disable Media Capabilities API (FF63+)
[WARNING] This *may* affect media performance if disabled, no one is sure
[1] https://github.com/WICG/media-capabilities
[2] https://wicg.github.io/media-capabilities/#security-privacy-considerations ***/
user_pref("media.media-capabilities.enabled", false);

/*** 2600: MISCELLANEOUS ***/
user_pref("_user.js.parrot", "2600 syntax error: the parrot's run down the curtain!");
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2 comments on commit f214e4b

@crssi
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@crssi crssi commented on f214e4b Nov 13, 2018

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I have tried some media with true and false and I haven't noticed any differences in a user feel perspective and also by the CPU consumption.
To my self: Maybe FF must be restarted on this pref change?

@earthlng
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Maybe FF must be restarted on this pref change?

nope, simply reloading a tab after (en/dis)abling is enough. source: just tested with a scratchpad script

I really don't think we need/should disable this because

  1. it doesn't expose that much atm (ie with the "screen" capabilities default false)
  • it has 2 functions decodingInfo and encodingInfo
  • decodingInfo can test for video and/or audio (combinations) and will return 3 booleans, supported, smooth and powerEfficient
  1. you might get served shitty quality vids
  2. disabling it is easily detectable and makes us stand out for no good reason because (almost?) the same information can be gathered by other means, see fe. https://bugzilla.mozilla.org/show_bug.cgi?id=1409664#c9

The information returned is identical to
1- canPlayType() for file
2- MediaSource.isTypeSupported for media-source
3- MediaRecorder.isTypeRecorder() for recordings.

canPlayType() demo/test page: http://www.leanbackplayer.com/test/h5mt.html

tldr: If someone is pretty unique because they can or can't play certain formats then that information can most likely be gathered even with MC disabled but having it disabled adds another bit of FP-ing info.

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