AMR Audio Encoding Problem

[jhorjus]

Im using the IPP Unified Speech Codec Interface (USCI) to encode PCM audio into AMR and then back into PCM. I need to get it working at all 8 AMR data rates 12.2k).

With my current setup it works great at the low bit rates (4.75kb/s, 5.15kb/s), but as I increase the bit-rate I start getting more and more distorted audio. Most of the setup code for the encoder/decoder I lifted directly from the example in the USC spec, but that example wasnt specific to AMR, which is different from most other codecs in that it uses multiple data rates.

This bizarre behavior is confusing meIve removed all of my bit-ordering and packaging code and these problems are still persistent; all Im doing is setting up the encoder, feeding it a PCM, and then giving the result directly to a decoder to make a new PCMagain this works fine at lower bit-rates, so I must be doing it at least partially right. Any ideas what I might be leaving out or doing wrong, or a simple example of using IPP to encode an AMR packet in the 12.2kb/s mode would be greatly appreciated

Recap: Using USCI codec IPP_GSMAMR to encode/decode audio.

4.75kb/s, 5.15kb/s Work Great.

5.90kb/s, 6.7kb/s, 7.4kb/s Sounds Bad.

7.95kb/s, 10.2kb/s, 12.2kb/s Completely Bad.

Any insights or examples greatly appreciated!!

[Vyacheslav_Baranniko]

Hi jhorjus

Did you try exactly the usc speech codec sample on your pcm input? Was quality of uncompressed wav file acceptable? Just to recall an intemediatebitstreamformat isnot comply anystandard other thanRIFF. So, you need just to feedoutput bitstream RIFF file after encoder directly to decoder.Actually, the USC GSMAMRhigh qualitywas verifiedbesides std vectors on huge additional test vectors for all possible bitrates and modes.

You may also tryExample B-1 Processing a Raw PCM with USC Codecfrom USC manual.

Would you attach your pcm, we will check it in our environment.

Thx, Slava