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Firing media events early for throttled downloads

From: Robert O'Callahan <robert@ocallahan.org>
Date: Thu, 2 Apr 2009 15:51:11 +1300
Message-ID: <11e306600904011951l49c10128td13f8f1731c8155d@mail.gmail.com>
To: public-html <public-html@w3.org>
Suppose a page waits for the "canplaythrough" or "load" events to fire on an
"autobuffer" media element before it starts playing the media. Then suppose
that a user-agent has a media data cache that's smaller than the size of the
media resource, so after loading some amount of the data the user-agent
decides to pause the download because the cache is full. Unfortunately, the
page will never start playing the media.

Authors can work around this by starting playback on receiving the "stalled"
event. (I'm assuming the the user agent is able to free up cache space for
played media data, so it will be able to resume the download and eventually
play the entire resource.) But that event could fire in other situations,
say due to temporary network stalls, when the page would not need to start
playback. It's also a trap for authors; in testing they might never notice
that the "stalled" handler is needed.

Should the spec allow the user-agent to set the media element ready state to
HAVE_ENOUGH_DATA, and to fire the "load" event, if it pauses the download
due to local resource constraints that may persist indefinitely?

Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
53:5-6]
Received on Thursday, 2 April 2009 02:51:52 GMT

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