[Freeswitch-users] G722 16k or 8k?

[Steve Underwood]

A documented bug becomes a feature. :-)

On 02/23/2012 11:46 PM, Stephen Dame wrote:
>
> Think I found my answer…..
>
> G.722 VoIP is typically carried in RTP 
> <http://en.wikipedia.org/wiki/Real-time_Transport_Protocol> payload 
> type 9.^[2] <http://en.wikipedia.org/wiki/G.722#cite_note-1> Note that 
> IANA 
> <http://en.wikipedia.org/wiki/Internet_Assigned_Numbers_Authority> 
> records the clock rate for type 9 G.722 as 8 kHz (instead of 16 kHz), 
> RFC3551^[3] <http://en.wikipedia.org/wiki/G.722#cite_note-2> clarifies 
> that this is due to a historical error and is retained in order to 
> maintain backward compatibility. Consequently correct implementations 
> represent the value 8,000 where required but encode and decode audio 
> at 16 kHz.
>
> Whilst G.722 allows for bitrates of 64, 56 and 48 kbit/s, in practice, 
> data is encoded at 64 kbit/s, with bits from the lower sub-band being 
> used to encode auxiliary data. The greater the number of bits 
> allocated to aux data, the lower the bit rate.
>
> Regards,
>
> Stephen
>
> *From:*freeswitch-users-bounces at lists.freeswitch.org 
> [mailto:freeswitch-users-bounces at lists.freeswitch.org] *On Behalf Of 
> *Stephen Dame
> *Sent:* Thursday, February 23, 2012 10:35 AM
> *To:* 'FreeSWITCH Users Help'
> *Subject:* [Freeswitch-users] G722 16k or 8k?
>
> Question on G722, trying to see if the quality of basic g.722 is much 
> better than the standard g729 or g711.
>
> Looking at wiki docs. “G722 - G722 16kHz using default 20ms ptime. 
> (multiples of 10)”
>
> However, when I connect to freeswitch using blink client I see 
> G722/8000? I thought this would be 16000. I know when I connect using 
> speex wb, it shows 16000.
>
> 2012-02-23 10:20:07.116606 [DEBUG] mod_sofia.c:750 Local SDP 
> sofia/internal/1004 at 107.XX.XX.XX:
>
> v=0
>
> o=FreeSWITCH 1329993171 1329993172 IN IP4 107.XX.XXX.XXX
>
> s=FreeSWITCH
>
> c=IN IP4 107.XX.XXX.XXX
>
> t=0 0
>
> m=audio 17236 RTP/AVP 9 101
>
> *a=rtpmap:9 G722/8000*
>
> a=rtpmap:101 telephone-event/8000
>
> a=fmtp:101 0-16
>
> a=silenceSupp:off - - - -
>
> a=ptime:20
>
> a=sendrecv
>
> Shouldn’t this be 16000?
>
> Thanks
>
> Stephen
>
>
> _________________________________________________________________________
> Professional FreeSWITCH Consulting Services:
> consulting at freeswitch.org
> http://www.freeswitchsolutions.com
>
> 
> 
>
> Official FreeSWITCH Sites
> http://www.freeswitch.org
> http://wiki.freeswitch.org
> http://www.cluecon.com
>
> FreeSWITCH-users mailing list
> FreeSWITCH-users at lists.freeswitch.org
> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
> http://www.freeswitch.org