[Live-devel] Request Headers in RTSP:SPEED Speed-up Delivery

[Ross Finlayson]

>Since the main reason of openRTSP is to record streams I doubt, this will 
>be any use, except when you can rebuild the recieved content to the normal 
>timeline.

Note the difference between the "Speed:" and "Scale:" headers.

The "Speed:" header doesn't change the data that gets sent - it just 
changes the bit rate at which it gets sent.  So, it would be useful to 
"openRTSP" if you were in a hurry, and wanted to download a (complete) 
stream at faster than real time.  (This is assuming, of course, that (i) 
the RTSP server supports this, and (ii) you have enough network capacity 
for this.)

The "Scale:" header, on the other hand, is used for things like fast 
forward or reverse play.  It *doesn't* change the bit rate at which the 
data gets sent.

So, for example
         Speed: 2.0
would cause the entire stream to be sent, but at 2x the normal bit rate, 
whereas
         Scale: 2.0
would cause the stream to be sent at the same bit rate, but in '2x fast 
forward' - e.g., by sending only every second video frame.

Note, BTW, that - as of version 2004.11.18 - the 
"RTSPClient::playMediaSession()" function includes an (optional) "scale" 
parameter.


	Ross Finlayson
	LIVE.COM
	<http://www.live.com/>