[Asterisk-Users] ADPCM 4-bit, 6 kHz

[Steve Underwood]

Yves Chouinard wrote:

>I found some posts regarding this issue dating of September 2003, but no
>real answer.
>
>The ADPCM format supported by Asterisk (the .vox files) is 4-bit, 8 kHz. I
>need 4-bit, 6 kHz, which is also a widespread Dialogic format, to help
>migration.
>
>Is there an existing format/codec for this? If not, can I make myself a
>shared object in /usr/lib/asterisk/modules? Is this easy??? :-(
>
>Thanks,
>
>Yves Chouinard
>Vox-Tel
>  
>
There is no support for this right now. However, as you say, the 
OKI/Dialogic 24kbps format is very widely used in the IVR business. It 
might be worth having a 6k -> 8K rate converter so the existing Dialogic 
32kbps code can also work with 24kbps Dialogic files.

P.S. Just saying 4-bit, 8 kHz or 4-bit, 6 kHz is meaningless. There are 
*many* ADPCM formats which fit those descriptions. The format is OKI 
ADPCM. Dialogic originally used OKI's ADPCM chips, although all recent 
cards implement the codec in a programmable DSP.

Regards,
Steve