[whatwg] Limiting the amount of downloaded but not watched video
bzbarsky at MIT.EDU
Tue Jan 18 14:00:12 PST 2011
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
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).
If the download speed is not stable enough, then it doesn't matter
whether on average you can stream the video, because the outliers will
still kill you.
> Mikko seems to suggest that it's the
> entire video times some multiplier, where that multiplier can be
> discovered by binary searching.
The multiplier should just be a function of the ratio of the stream
bitrate and the available download bandwidth if those are both constant.
But note that available download bandwidth is non-constant. A number of
cable services around here, at least, seem to do something where they
give you N bytes per second for the first K bytes of a download
(presumably that's a single connection, but who knows how they define
it) and N/2 or N/3 or N/10 bytes per second for the rest of the
download. The connection is sold as an N/2 or N/3 or N/10 connection,
not a connection that can actually produce N bytes per second. But
nevertheless, the average download rate will differ depending on the
file size, and hence the multiplier is different for different file sizes.
Given that I think the random speedup bit is per-connection, I doubt
that this can be discovered with some sort of binary search, though.
Agreed on that.
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