Decoding GSM-AMR stream ...

[Maciej_K_]

Hi,

I'm trying to decode GSM-AMR 12200bps stream :

a: rtpmap: 97 AMR/8000
a=fmtp: 97 decode_buf=400; octet-align=1

with IPP5.2 usc_codec, but on output I hear only gurgling. I have universal usc decoder and only switch function set, frequency and bitrate. I successfully decoded G722.1 and G729A with this method. Are there special parameters or decoding method needed for this codec or should it work as any other codec ? Thanks in advance.

[Igor_B_Intel1]

Hi,

usc_speech_codec sample only supports bitstream in its native format. RTP payload format for GSM AMRdiffers from the native format. You should write bitstream converter.

Please, take a look to the newly developed sample umc_speech_rtp_codec in IPP5.3 beta. It supports GSM AMR and AMR WB codecsand can decode RTP stream stored in rtpdump format. There you can find example of the bitstream converter.

As for G729A: its RTP payload format is equal to the usc_speech_codec bitstream format.

Igor S. Belyakov