Decoding AMR

Harald Welte laforge at
Thu Feb 28 15:43:08 UTC 2013

On Thu, Feb 28, 2013 at 05:54:27PM +0300, Akib Sayyed wrote:
> I tried studying TSM code layer1 and Osmocom layer1 for purpose of
> implementing them in cellphone it self but i as far as i know that init of
> some variables required for amr are completed  but couldnt be able to
> figure out what exactly part remaining .

I remain with what I stated before:

you first need to understand the detailed operation of AMR in the
context of GSM by studying the specs.  I'm mostly talking about the
encoding of the various bits, signalling of codec mode changes, etc. -
not the mathematical background of the actual voice codec.  It might
also help to study related documents like the IF2 and RTP formats for

Only with that backgorund knowledge _and_ knowledge of the TSM30 L1 code
as well as traces from actual AMR calls on A-bis and possibly Um, I
think you will be in a position to fully understand the porblem and
implement what is needed.

Asking for somebody to explain every little detail for you is not the
way to solve any problem.  If Sylvian, Dieter, Andreas or I sit down,
read the code + dosc, and give minute instructions what needs to be
done, this consumes more of our time than if we actuall implement it

If you have _specific_ technical questions, please come back to the
list.  If you have  a specific question, please include a precise
reference to the chapter/section of the specification (+ exact version
of the document), the exact function or data structure you refer to.

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

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