[whatwg] Limiting the amount of downloaded but not watched video

Glenn Maynard glenn at zewt.org
Sun Jan 23 03:13:15 PST 2011

On Sun, Jan 23, 2011 at 5:24 AM, Philip Jägenstedt <philipj at opera.com>
>> I do think that in the basic case of a user pressing play on a video
>> player, it's good to be able to make that respond instantly rather
>> than waiting for a round-trip to begin playing.
> Have you found this to be an actual problem in Firefox, which does suspend
> download after reaching HAVE_METADATA?

It's not a big problem, but a user experience one: user interfaces are
cleaner when they're immediately responsive.  I'd sooner give a crisp
interface to users than one that feels delayed.

>> Another use case is the background of a game, where you want the video
>> ready to start when gameplay begins.
> For that you should really use <audio preload=auto>, no?

Not if all you want is for the video to start with the rest of the game, and
not to download the whole video.

They're both minor, of course; helpful side-effects of preload=buffer, not
sufficient justifications by themselves.

Hmm.  To get this effect without preload=buffer, you could set preload=auto,
watch the buffered attribute to see when some data is actually downloaded,
then set it to preload=metadata to stop autoloading.  That's a minor hack,
and would need to watch out for browsers that don't autoload on
preload=auto, but it's probably good enough for the above cases.  It'd only
work if runtime changes to preload are applied, which would also be needed
for scripts to implement "preload=auto only when paused".

Glenn Maynard

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