AMR-WB vocoder in HL8548


#1

AMR-WB vocoder support is declared in “Product Technical Specification” for AirPrime HL8548 module.
This vocoder uses 16kS/s sampling rate.
But PCM bus of HL8548 module don’t suport 16kS/s sampling rate.
Fragment from “AT Commands Interface Guide”: The sampling rate is fixed to 8kS/s.
How it possible?


#2

Ngm,

AMR-WB uses a 16kbps data stream, it does not use 16KS/s, this comes into the unit in a compressed audio format which the unit then decompresses using its on board algorithms and turn into a full PCM data stream so the two are not comparable. The AMR WB bit just allow the unit to make that stream sound more like the the person at the other end (since all of the audio coding in mobile comms is lossy).

Regards

Matt


#3

Did you read 3GPP TS 26.190 - “Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Transcoding functions” document?

Fragment from this document: “The sampling rate is 16 000 samples/s leading to a bit rate for the encoded bit stream of 6.60, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05 or 23.85 kbit/s”.