RTP Depacketizer for AMR Payload

AMR has now become the de-facto standard for the 3G Voice Telephony. The voice quality of the decoded speech is admirably high. AMR standard infact provides the flexibility of 8 bitrates, which can be adapted based on the network conditions, bandwidth availability, etc.

Now lets understand what AMR is, in brief.

AMR codecs are basically of two types.
1) A narrow band Codec called AMR-NB:
The narrow band codec employes a sampling frequency of 8000Hz and encodes speech frames of 20 milli seconds duration. So, each encoded speech frame represents 160 samples of the original speech. AMR-NB is a multi-mode codec that supports the speech encoding at 8 different bitrates between 4.75kbps and 12.2kbps.

2) A Wide band Codec called AMR-WB:
The Wideband codec employes a sampling frequency of 16000Hz and the duration of the encoded speech frames is 20 milli seconds. Because of the higher sampling rate employed, the bitrates are higher as well. AMR-WB supports 9 different bitrates between 6.6kbps and 23.85kbps.

TO BE CONTINUED.............