Re: [codec] #16: Multicast?

"Raymond (Juin-Hwey) Chen" <> Sun, 25 April 2010 00:37 UTC

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From: "Raymond (Juin-Hwey) Chen" <>
To: Koen Vos <>, "" <>
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Subject: Re: [codec] #16: Multicast?
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On Saturday, April 24, 2010 at 1:56 PM, Koen Vos Wrote:

> Sure - for certain frame sizes.  But 1 ms frames won't give you 5 ms  
> one-way delay.

Of course not.  That's why I added the sentence: "Even if you use a longer jitter buffer, the one-way delay is still unlikely to go above 100 ms, ..." in that email you quoted. I knew that below a certain threshold of the codec frame size, you most likely want to use more frames of jitter buffer delay, thus my added sentence above.  My main point, though, is not in the exact one-way delay value for a codec with a 5 ms frame size, but rather that with a 5 ms frame size you can get a much lower one-way delay than with a 20 ms frame size.  I don't think anyone can credibly argue that this statement is untrue.

> For a well-designed system and a typical Internet connection:
> - most delay comes from the network and is not codec related, and
> - one-way delay grows almost linearly with frame size.

Doesn't your last line above contradicts with the second last line? I am a bit confused about what you are trying to say.  

> Afaik, only RTP headers can be compressed between arbitrary Internet  
> end points.  You're still stuck with IP and UDP headers.

I am aware of a header compression technology for VoIP over Cable applications that can compress the header size to a very small fraction of the original size, but it is probably not widely used.