Re: [codec] #16: Multicast?

"Raymond (Juin-Hwey) Chen" <> Mon, 10 May 2010 21:27 UTC

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From: "Raymond (Juin-Hwey) Chen" <>
To: "Kevin P. Fleming" <>, "" <>
Date: Mon, 10 May 2010 14:24:02 -0700
Thread-Topic: [codec] #16: Multicast?
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Subject: Re: [codec] #16: Multicast?
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I should have clarified:
I am not proposing that we limit the complexity of all IETF codec modes 
to 10 to 20 MIPS.  That would be unreasonable, especially for high-
sampling-rate and high-fidelity applications. 

Just like we seemed to have reached a consensus that a low-delay mode 
is necessary to address delay-sensitive applications (as is specified 
in the codec requirement document), we can also have a low-complexity 
mode to address complexity-sensitive applications such as low-
end/mobile devices and gateways. It is for such a low-complexity mode 
that 10 - 20 MIPS is a good target to shoot for, at least for 
narrowband and wideband. (Super-wideband and full-band can be layered 
coding on top of that and do not need to be subject to this 10 - 20 
MIPS target.) For other coding modes that require more processing 
power, this 10 - 20 MIPS target obviously would not apply.

Also, if we don't like to have too many different coding modes, and if 
some modes can be combined, for example, if the low-delay mode can also 
achieve low complexity, then we can combine the low-delay mode and the 
low-complexity mode into a single mode.  We can have another mode 
that's more efficient in bit-rate but may have higher delay and 
complexity to address those applications that are less sensitive 
to delay and complexity.


-----Original Message-----
From: [] On Behalf Of Raymond (Juin-Hwey) Chen
Sent: Monday, May 10, 2010 1:26 PM
To: Kevin P. Fleming;
Subject: Re: [codec] #16: Multicast?

Hi Kevin,

I completely agree with you that the IETF codec development should not 
be constrained by a low-complexity device designed in 2009 or earlier, 
and we should look toward the time frame of 2012 and 2013 instead.  

In my previous emails I have indicated that due to many reasons, over 
the last several years the processing power of Bluetooth headsets has 
been increasing at a rate much slower than what's predicted by Moore's 
Law, and it doesn't look like this will change significantly in the next 
few years.  I also said that for the current-generation Bluetooth 
headset chips, the maximum codec complexity it can support is probably 
somewhere around 5 MIPS on a 16-bit fixed-point DSP, and by the time the 
IETF codec becomes a standard, the number may go up to 10 MIPS, or 15 
MIPS at most.  

Thus, if we want mono Bluetooth headsets in the FUTURE (i.e. in the next 
several years) to be able to run the IETF codec in the narrowband or 
wideband mode at least, a good complexity target to shoot for is 10 to 
20 MIPS on a fixed-point DSP.


-----Original Message-----
From: [] On Behalf Of Kevin P. Fleming
Sent: Monday, May 10, 2010 12:33 PM
Subject: Re: [codec] #16: Multicast?

On 05/10/2010 02:11 PM, Raymond (Juin-Hwey) Chen wrote:

> Considering that there are a very large number of Bluetooth headset users and that the current Bluetooth headsets can already be used for making VoIP phone calls, it would be great if the IETF codec can be implemented in future Bluetooth headsets to avoid the additional coding distortion and delay associated with transcoding. However, with that said, I didn't mean to push a "Bluetooth mode" for the IETF codec. I merely wanted to use Bluetooth headset as an example to make a point that a low codec complexity is desirable and a high codec complexity can have negative consequences.

This is all perfectly reasonable, but given the likely timeframe we are
talking about for this codec to be produced and published as a
standards-track RFC, the definition of 'low complexity' in this
discussion is really talking about the 2012-2013 version of 'low
complexity', not today's. It seems highly likely that the MIPS capacity
of the DSPs designed into Bluetooth headsets in 2012 will be vastly
greater than what is used today, if there is an application to take
advantage of the additional MIPS.

I'd hate to see this codec's development constrained in any significant
way by the requirements of a low-complexity device designed in 2009 or

Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber:
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