I have downloaded 3gpp's AMR-WB+ open source code and would like to encoder a file at 16KHz stereo. My input is a 16KHz stereo file. I have given these encoder options:
mi=24 and isf=0.625 corresponding to 16KHz stereo modes. But I see that the encoder is running @ 25.6KHz. Shouldn't it be @ 16K rate? Also there is an oversampling being done @48k before encoder loop.
However the encoded bitstream has the isf factor as 3 which corresponds to 16KHz. When I decoded this file, the output is a 48KHz rather that a 16KHz. Does AMR-WB+ encoder and decoder not support native sampling rate encoding / decoding? It would be great if experts can throw some light on this.