[Freeswitch-users] G722 8000 vs 16000

[Sluschny, Thomas]

Hi,

i want to use G.722 with its wide audio bandwith of 7kHz.
But i have found that FreeSwitch resamples always from 16000 to 8000
Samples/s if i connect a "standard device", i. e. a SIP device with a
"G722:9/8000" in its SDP.

On the other side it is possible to use full bandwith if there is a
"G722:9/16000" in SDP.

I think this is not correct!
FreeSwitch should always use 16000S/s and also use "G722:9/8000" in SDP!

Read RFC3551, 4.5.2:
...Even though the actual sampling rate for G.722 audio is 16,000 Hz,
   the RTP clock rate for the G722 payload format is 8,000 Hz because
   that value was erroneously assigned in RFC 1890 and must remain
   unchanged for backward compatibility.
...

I tried the 16kHz-implementation with a SIP phone (siemens optipoint 410
with "G722:9/8000") and it seems to work.

In the g722.h file is mentioned that the 8k option is used for fast and
flexible interworking with narrow band telephony. I think this is a
special case (we also support G711 for this). Our default should be
16000S/s and "G722:9/8000".

What do u think?

Thomas