Natural Access AMR codec information
- Nathaniel Halbrooks
Supported Frame Types and Data Rates
Dialogic CG series Media Boards support the following rates with the AMR codec:
Frame Type Data Rate Payload Size
---------- --------- ------------
0 (default) 12.20 kbps 31 octets
1 10.20 kbps 26 octets
2 7.95 kbps 21 octets
3 7.40 kbps 19 octets
4 6.70 kbps 18 octets
5 5.90 kbps 16 octets
6 5.15 kbps 14 octets
7 4.75 kbps 13 octets
8 1.80 kbps 6 octets (Comfort noise - SID)Â Limitation - Mode adaptation as specified in RFC 3267
The readme file mentions this limitation:
Only the octet aligned payload format is supported. "Bandwidth efficient" mode is not supported.
How rate adaptation requests are handled by the Dialogic CG Series AMR codec
If the remote side sends a Codec Mode Request (CMR) (for example, to change mode from 12.20 to to 10.20 kbps) and changes the rate, then the CG decoder properly handles the AMR frames.Â
However, the Dialogic CG series encoder will continue to send at the initially configured rate (in this example, 12.2 kbps). Â If CMR were fully implemented then the CG encoder would change to sending frames at the 10.2 kbps rate.
Product List
All Dialogic CG series Media Boards
Glossary of Acronyms / Terms
AMR -- Adaptive Multi Rate.
RFC -- Request for Comments
SID -- Silence Insertion Descriptor
CMR -- Codec Mode Request