Dan wrote:
----- Original Message ----- From: "Steve Underwood" <[EMAIL PROTECTED]>The GSM 06.10 codec is *much* less complex than G.729. Mark said he had over 200 channels of GSM running on a server a long time ago, but I don't know what that machine was. 06.10 isn't that great a codec, though. I don't think it is used very much on the GSM networks these days. Most of the time they use the enhanced full rate (EFR) or half rate codecs.
To: <[EMAIL PROTECTED]>
Sent: Wednesday, August 13, 2003 9:49 AM
Subject: Re: [Asterisk-Users] Open G.729A codec
Steve Underwood wrote: After writing this I got curious about how fast/slow the ITU reference code really is. I built and ran the G.729A reference code on a 2.4GHz Xeon machine, running RedHat 9. Its actually a dual Xeon, but the test is only able to use 1 CPU.
G.729A is the fixed point reduced complexity version of G.729. Reduced complexity means it needs about half the MIPs of the more complex version. I compressed and decompressed a 3.5 minute file of 16 bit linear speech. It took 25 seconds to compress and about 5 seconds to decompress. That ratio seems about right for a codec of this type. So, using this code you can only do 7 bidirectional channels, using 100% of a 2.4GHz Xeon. Not exactly great, huh?
Perhaps I should try the floating point version. That might perform somewhat better on an x86 machine, as any scaling and saturation steps need not be performed.
For comparison, can anyone tell me how fast the VoiceAge codec runs? If is isn't a *lot* faster than that I would be rather surprised. It should be algorithmically more efficient, and I assume as a commercial product it should be using MMX, SSE and/or SSE2.
There is any test made in the same conditions using Asterisk's GSM codec? I am interested in the scaling possibilities when using hardware IP phones with G.711 codec (like Cisco's 79x0, ATA, Budgetone, SNoM, etc.) and remote IAX connections plus all the local voice prompts and voicemail using GSM codec.
I just tried the ITU reference floating point code for G.729. Its considerably faster. It encoded a 3.5 minute speech file in less than 5s, and decompressed it in about 1s.
I have no idea whether you are permitted to base an implementation on anything in the reference code. The code says its copyright by "AT&T, France Telecom, NTT, University of Sherbrooke, Conexant, Ericsson. All rights reserved." but that doesn't make a whole lot of sense. Once you have the code, it is mearly impossible to make a clean room implementation, and its hard to get a clean room implementation bit accurate unless you play with the reference code. I couldn't find a clear statement about what you are permitted to do. I assume as long as you cough up the patent licence fees they wouldn't care too much, but who knows.
Regards, Steve
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