[vlc-devel] [vlc-commits] commit: stream_filter/httplive.c: HTTP Live Streaming (Jean-Paul Saman )

[Rémi Denis-Courmont]

On Wed, 13 Oct 2010 23:06:22 +0200, David Glaude <david.glaude at gmail.com>
wrote:
> Le 13 octobre 2010 11:53, Rémi Denis-Courmont <remi at remlab.net> a écrit
:
> 
>> On Wed, 13 Oct 2010 09:48:16 +0200, Jean-Paul Saman <jpsaman at gmail.com>
>> wrote:
>> >> - What is the protocol to detect bw_up and bw_down? Was that not too
>> >> difficult with VLC arch?
>> >
>> > It is fairly simple, measure the download speed per segment and base a
>> > decision on that.
>> > Since the stream_filter initiates the download itself it can also
>> > measure how long that takes and
>> > calculate the average download speed in terms of bandwidth of the
> stream.
>>
>> This assumes that the HTTP server will agree to serve the file at a much
>> larger TCP bandwidth than playback bandwidth of the media.
>>
> I think we are assuming that the HTTP server is tuned or design to serve
> Apple HTTP streaming and/or that a CDN is in use for that.

That's exactly the kind of server I would expect perform rate limiting.

> Why would someone try to do Apple HTTP streaming and limit the bandwidth
> per connection below the highest bitrate offered?

Because bandwidth is expensive on the Internet. Most Flash-based video
sites already do rate limiting. With a fixed bandwidth, less bandwidth per
users means more users for the same price.

Sure, it would be idiotic to serve a high bit rate file at less than the
its native bit rate. But what prevents doing that for a low bit rate file?

>> Thus there is a risk that even the slightest transient congestion
>> might make VLC needless scale down the video.
>>
> With Apple HTTP streaming you are suppose to have a few chunk of advance
> (when the user is not seeking in every direction) and at least for LIVE
> streaming that is what you do.
> So you can detect without problem that the download speed is degrading
and
> adapt.

My point is that you might not see the download speed improving. Of course
you can see the download speed degrading.

-- 
Rémi Denis-Courmont
http://www.remlab.net
http://fi.linkedin.com/in/remidenis