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FW: [w3c/media-source] Restore auto-revoking behavior of createObjectURL(MediaSource) to revert breaking change introducing memory leaks (#156)

From: Paul Cotton <Paul.Cotton@microsoft.com>
Date: Fri, 2 Sep 2016 01:06:35 +0000
To: "Matthew Wolenetz <wolenetz@google.com> (wolenetz@google.com)" <wolenetz@google.com>, Mark Watson <watsonm@netflix.com>, "Jerry Smith (WPT)" <jdsmith@microsoft.com>
CC: "public-hme-editors@w3.org" <public-hme-editors@w3.org>
Message-ID: <BN6PR03MB2724CC2927BFC19A39651A14EAE50@BN6PR03MB2724.namprd03.prod.outlook.com>
How are the Editors planning to handle this request?

From: Karl Tomlinson [mailto:notifications@github.com]
Sent: Wednesday, August 31, 2016 7:42 PM
To: w3c/media-source <media-source@noreply.github.com>
Subject: [w3c/media-source] Restore auto-revoking behavior of createObjectURL(MediaSource) to revert breaking change introducing memory leaks (#156)

#10 (comment)<https://github.com/w3c/media-source/issues/10#issuecomment-151735372>
pointed out that removing the auto-revoking behavior would be a breaking

#10 (comment)<https://github.com/w3c/media-source/issues/10#issuecomment-189219426>
used two arguments to say this would not be a breaking change:

1.     That clients already needed to revoke explicitly anyway, due to a bug in
the File API spec.

2.     That three existing UAs did not implement the auto-revoking behavior.

Firefox does auto-revoke, and so 2 was incorrect. This is tested in

I am also not convinced by 1. Whether the precise time of revocation was
clear or not, it was clear that the intention was that the client need not

MSE does not need object URLs of infinite lifetime because these merely
provide a mechanism of associating the MediaSource with a media element.

As referenced in
#10 (comment)<https://github.com/w3c/media-source/issues/10#issuecomment-201024017>
removing the auto revocation leads to memory leaks.
These leaks extend to objects affecting and affected by the MediaSource object.

The second sentence of
#10 (comment)<https://github.com/w3c/media-source/issues/10#issuecomment-208923486>
is also incorrect because Firefox, at least, revokes the object URL on the
next stable state, and so there is nothing to keep the objects alive.

I don't know the reasons for requiring explicit revocation of File URLs, but I
doubt they apply to MSE.

Keeping track of strings for object URLs created, or immediately explicitly
revoking, is an unnecessary burden for clients, one that is unexpected in a
garbage collected world. This outweighs benefits of a breaking change to
be consistent with the File API.

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Received on Friday, 2 September 2016 01:07:11 UTC

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