On 01/06/2011 12:05 AM, Kevin P. Fleming wrote:
On 01/05/2011 07:07 AM, Steve Underwood wrote:
On 01/05/2011 03:29 PM, Bruce B wrote:
Hi Everyone,

1- Are the Siren7 and Siren14 the G.722 HD voice codecs?
2- Are these codecs only for Polycom units or are they universal
across all other SIP phones that advertise the HD voice codec like
3- What is the main difference between the two and is it advisable to
run these over the INTERnet (not INTRAnet)?

The G.722 codec in * is G.722. The Siren7 codec in * is probably not
Siren 7, but G.722.1. G.722.1 is very similar to Siren7, but uses a
different code in the SDP and has some minor differences in the codec.
The name G.722.1 may look similar to G.722, but the codecs bear no
relation to each other. The Siren14 codec in * is probably not Siren14,
but G.722.1C. G.722.1C is very similar to Siren14, but like
Siren7/G.722.1 the SDP code is different, and there are minor
differences in the codec.

Asterisk actually supports both the Siren* and G.722.1* names in SDP negotiations. I wasn't aware there were bitstream incompatibilities between the Siren* and G.722.1* variants, even though the code may be slightly different... so Asterisk uses a single codec module for both variants.

I am unclear how compatible or incompatible the bitstreams may be. What I know (from implementing these codecs) is that the source code Polycom provide licencees, as the basis for developing their own G.722.1 and G.722.1C codecs, has several comments referring to things not being quite the same as Siren7/Siren14. However, they don't hand out the actual Siren7/Siren14 source code, so I don't know how much divergence there is.


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