Codec Complexity and Compression

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Codec Complexity and Compression

by Amj » Wed Oct 10, 2012 1:31 pm

Hi everyone

As we know that codec can either be high in complexity or medium and if we use flex mode then we can use either of the complexity codec. But i have some doubts regarding these codecs and would really appreciate if someone can clarify them.

I have read in one of the documents that
The codecs under the High Complexity category use 40 MIPS per call. And
The codecs under the medium complexity category use 30 MIPS per call.

High Complexity Codecs are
G.723.1, G.728, G.729, G.729b, GSM-EFR and Modem Relay

Medium Complexity Codecs are
G.711, g.729a, G.729ab, G.726, GSM-FR and Fax Relay

So its mean if i select high complexity mode then i will not have the option to select G711 ? (as it is medium complex codec). Moreover, it should not matter which high complex codec i use, all will use 40 MIPs per call...right?? This is bit strange coz G.723.1 compresses voice at 5300 bps and G728 compresses at 16000 bps. In my point of view, G723.1 should have used more MIPs per call than G728 as it compresses more but according to above statement, since both are high complexity codec therefore both should use 40 MIPs per call?

Similarly, G711 should use 30 MIPs per call as it is a medium complexity codec but when i use it under flex mode, it only consumes 15 MIPs per call?? That is the reason it states that u can place 16 G711 calls per DSP under flex mode (as it only uses 15 MIPs per call) and only 8 under medium mode (30 MIPs per call) so then which type of codec exactly G711 is??

Last but not least, according to the following cisco article ... 6710.shtml

"all the medium complexity codecs can also be run in high complexity mode, but fewer (usually half) of the channels are available per DSP." According to this statement, i should be able to use G711, G729a and other medium complex codec under high complexity mode but only with 60 MIPs per call??

Thanx in advance