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

Glenn Maynard glenn at zewt.org
Tue Jan 18 15:19:15 PST 2011

On Tue, Jan 18, 2011 at 5:00 PM, Boris Zbarsky <bzbarsky at mit.edu> wrote:

> On 1/18/11 4:37 PM, Glenn Maynard wrote:
>> If you don't have enough bandwidth, then the necessary buffer size is
>> effectively the entire video[1]
> No, it's really not.  Your footnote is, of course, correct.
> If my bandwidth is such that I can download the video in 2 hours, and it's
> one hour long, then letting me start playing after 1.5 hours of downloading
> seems perfectly safe to me, if the download speed is stable enough (has a 2x
> margin of safety).

I'd tend--both as a user and as a web developer--to err the other way, and
always download the whole video if the connection isn't fast enough to
reliably stream it.  The failure mode otherwise is very bad: the user's
movie underruns two hours in, possibly resulting in a box of popcorn being
hurled angrily at the TV.  Either way, it's a judgement call based on user
experience priorities, so web pages should have some influence over the

Note that we're not actually describing the "maximum prebuffer" value (the
topic of the thread), but rather the "minimum prebuffer", eg. Flash's
bufferTime value from Zachary's mail.  In both of the above cases you'd
probably want the maximumPrebuffer value to be unlimited.

Glenn Maynard

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