modulated data over GSM voice (was Re: Data over normal GSM call)

Andy Green andy at
Tue Apr 15 09:49:22 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:

| While stating it being unlikely, I have no dout that it can be done,
| given enough effort.  But it requires a lot of work by somebody with

Alright, that's all I was saying too.

| lots of knowledge and experience in signal processing, baseband digital
| communications, modulation schemes, the intrinsic properties of the
| various codecs involved.
| Oh, and even if you do that, you still have to manage to implement it
| all based on fixed-point math, make it run next to all the other things
| on the ARM920T CPU core :)

Hey in my last job I did this, there is a great GPL library called
hawkvoice that has integer GSM codec and plenty of others.

Four encode instances worked great on no-FP 180MHz ARM at way less than
100% CPU.

| Not to forget the testing on the various codecs that are in use.  GSM
| networks are getting more diverse every year.  With some carriers now

"Impractical"... not worth the time to look at... I guess so... but it's
not the same as "impossible".

- -Andy
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