Re: [codec] #16: Multicast?

"Raymond (Juin-Hwey) Chen" <> Wed, 12 May 2010 18:48 UTC

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From: "Raymond (Juin-Hwey) Chen" <>
To: Cullen Jennings <>
Date: Wed, 12 May 2010 11:28:37 -0700
Thread-Topic: [codec] #16: Multicast?
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Subject: Re: [codec] #16: Multicast?
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Hi Cullen,

Hmm... That's interesting.  Would you please share more details of 
your measurement equipment setup, the codec used, the codec frame 
size, the number of codec frames in each packet, the way you 
measured the delay, and the measured delay value, etc.?  

I didn't come up with this 3*(codec frame size) delay number for IP 
phones myself.  A very senior technical lead in Broadcom's IP phone 
chips group told me that, and Broadcom is currently the #1 world-
wide market share leader in IP phone chips, accounting for more than 
half of the world's IP phone chip shipments. Most of the world's 
tier-1 IP phone manufacturers use our IP phone chips at least in 
some of their product lines.

I would be very interested to learn more about your measurements to 
try to reconcile these seemingly contradictory statements from two 
different sources.  Thanks.

Best Regards,


-----Original Message-----
From: Cullen Jennings [] 
Sent: Wednesday, May 12, 2010 8:00 AM
To: Raymond (Juin-Hwey) Chen
Cc: Koen Vos;
Subject: Re: [codec] #16: Multicast?

On May 4, 2010, at 7:15 PM, Raymond (Juin-Hwey) Chen wrote:

> the 3*(codec frame size) delay is very real for IP phone

This does not match the measurements I have. And I certainly don't have 100+ year voip experience but I do have two of the #1 selling enterprise phones connected to an oscilloscope. Test with other phones suggest most the major vendors of IP hard phones have fairly comparable performance when it comes to delay.