[Live-devel] Encrypted program stream by RTP

[Mike Yan]

Thank you for your answers.
Actually, I don't need any encryption or decryption, all I want is to use
"SimpleRTPSink" as transportation protocol. I just want to know what
"preferredFrameSize" and "playTimePerFrame" represent for and how to
calculate them from the information of *.mpg file.


>I was interested by this message. Base on it, I have some questions (maybe
>it's too dummy question, anyway I am new guy of this industry).
>If I use "SimpleRTPSink" to *.mpg file instead of using
>"MPEG1or2VideoRTPSink", how to get the "preferredFrameSize" and
>"playTimePerFrame" parameters base on existing *.mpg file.

You'd have to figure these out yourself.  I.e., given a ".mpg" file, you'd 
have to decide
1/ What (fixed) size chunks of this file do you want to encrypt at a time 
(this size should be < ~1400, so that it'll fit in a single RTP packet), and
2/ Given this chunk size, what is each chunk's average 'duration' (i.e., 
based on the average data rate of the file).

Note that this suggested method of doing encrypted RTP- encrypting chunks 
of the input, and sending them as opaque data (as far as RTP is concerned) 
- is basically just a quick-and-dirty hack, is not the proper way to do 
encrypted RTP.  (The proper way to do encrypted RTP is to use the new SRTP 
(secure RTP) IETF specification, which encrypts RTP payloads, but preserves 
existing RTP payload formats.  SRTP is on our 'to do' list, but (you know 
the story...).)


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

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