YouTube style throttling in Flash

Question

I may be completely insane on this one, but it seems like the download/buffer rate of YouTube videos is faster at the beginning and the further the buffer point gets from the currently playing mark, the slower buffering goes.

Am I crazy, or does it work this way for everyone else?

Assuming the latter, any theories on how they do it? Is it server-side or client-side? I would think it would have to be client-side, but who knows? Not me, that's why I'm asking!

Answer 1

From what I see from a wireshark dump, they buffer content by doing multiple requests (with a parameter "range") to the server. The client only requests the next part when he needs it.

GET /videoplayback?
sver=3&
key=yt1&
sparams=algorithm%2Cburst%2Ccp%2Cfactor%2Cid%2Cip%2Cipbits%2Citag%2Csource%2Cupn%2Cexpire&
algorithm=throttle-factor&
upn=L4m-ID0n0V0&
expire=1334882299&
factor=1.25&
ipbits=8&
ip=77.0.0.0&
fexp=912300%2C919303%2C911623&
source=youtube&
range=8908800-10690559&
cp=U0hSSVhTUF9OU0NOMl9QTVRDOjhGTXRjbEpBNzls&
burst=40&
signature=20F9219AACD9249B3517F56ECFE8B12C6B001D2F.BDDD25B61745E0F6E0BBAC7E792C121AA67A4C7C&
keepalive=yes&
itag=34&
cm2=0&
id=9cc8ae37c50b77f7 HTTP/1.1

Otherwise, this kind of bandwidth throttling is only doable if the client 'has the control' over the server, i.e. either requests what he knows he needs (ex: Youtube progressive download), or tell the server regularly where he is (ex: RTCP/RTMP / RTP streaming).

Answer 2

This is done on the server side, there is no way to do it on the client side.

There are many different ways to serve videos, so it will depend on what server technology you are using if you want to set it up yourself, or you could just use something like RTMP (via Flash media server or Red 5, etc.).