AMR support

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Harald Welte laforge at
Sun Oct 23 07:09:00 UTC 2011

Hi Aegean,

On Sat, Oct 22, 2011 at 07:32:20PM +0800, Aegean Chou wrote:
> 	The osmocomBB no AMR support yet now (only FR, HR and EFR).

this is correct.

> 	i checked the product datasheet, the C123 can support AMR from
> 	the beginning.  does anyone can give me some information to
> 	patch it?

AMR in general is relatively complex, at least at least if you want to
implement it in a compliant way.  There is not only the 'adaptive'
aspect, i.e. the negotiation of different codec modes with CMR/CMI/CMC
and the associated CmiPhase, but also the RATSCCH signalling for TFO.

Furthermore, the situation gets slightly more complicated as the Calypso
DSP ROM firmware apparently doesn't support AMR out-of-the-box but needs
some DSP code patches.

While we already have support for applying such patches, we don't have a
license to distribute such patches, i.e. we cannot include them in
OsmocomBB without being in copyright violation.

So the correct way of implementing this is:
* decide which DSP patch to use (from original firmware)
* write a script that can extract it out of the original firmware
* include such a script in OsmocomBB
* implement the DSP API / L1 related aspects for AMR in Calypso
  (by looking at TSM30 source code, or legal forms of reverse
   engineering the original firmware of e.g. a C123)

If you would like to contribute patches/code for any of this work, we
would be more than happy to review and merge them.

- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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