tetra Digest, Vol 9, Issue 3

Graham Palmer graham.palmer69 at yahoo.co.uk
Sat Sep 24 18:56:05 UTC 2011


Hi again.
We have the etsi cdecoder and speech decoder which works fine with sample code
what we need is to link it with real time bitstream from osmo tetra decode.
I understood this had already been achieved with Dieter's proof of concept
code. Any chance of  viewing this code even if incomplete ?.
regards.
graham



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From: "tetra-request at lists.osmocom.org" <tetra-request at lists.osmocom.org>
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Sent: Saturday, 24 September 2011, 16:04
Subject: tetra Digest, Vol 9, Issue 3



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Today's Topics:

   1. Re: tetra Digest, Vol 9, Issue 2 (Graham Palmer)
   2. Re: play the voice signal ? (Dieter Spaar)
   3. Re: play the voice signal ? (Pepijn van den Berkhof)
   4. Re[2]: play the voice signal ? (Mccauley)
   5. Re: play the voice signal ? (Holger Hans Peter Freyther)
   6. Re: play the voice signal ? (Dieter Spaar)
   7. tetra voice (fe8769)

Hi all
I am still learning this level of coding.
I am struggling to get the descrambled bitstream from the lower mac to the 

channel decoder of the etsi codec. My setup has no problem decoding the data
and reading it with Wireshark. Any help would be appreciated.
Best regards.
Graham



________________________________
From: "tetra-request at lists.osmocom.org" <tetra-request at lists.osmocom.org>
To: tetra at lists.osmocom.org
Sent: Saturday, 24 September 2011, 11:00
Subject: tetra Digest, Vol 9, Issue 2



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Today's Topics:

   1. play the voice signal ? (Bigsat)
   2. Re: play the voice signal ? (Dieter Spaar)
   3. Re: play the voice signal ? (Pepijn van den Berkhof)
hi,

I am using "fcdp-tetra_demod.py" with my funcube dongle and i can decode datas. The networks in my place are unencrypted.
I saw on the "Dieter Spaar's blog" :

"I also implemented some proof of concept code which allows decoding speech traffic and converting it to raw audio using the TETRA reference codec. Please note that this cannot be used to listen to encrypted TETRA traffic, it only works if no encryption is used. "

Is it possible to release some part of the code necessary to decode
 Tetra voice or give some explaination of Gsmtap usage ?

thanks for answer



Hello Bigsat,

On Fri, 23 Sep 2011 13:49:43 +0200, "Bigsat" <bigsat at gmail.com> wrote:
> 
> Is it possible to release some part of the code necessary to decode 
> Tetra voice or give some explaination of Gsmtap usage ?
> 

Just in case, I have sent my "proof of concept" modification
for voice decoding to the authors of Osmocom TETRA for proper
integration a while ago. As far as I am aware the current
source code should be able to decode voice or at least contain
the instructions how to do it (the ETSI reference codec is most
certainly not included for copyright reasons).

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                          spaar at mirider.augusta.de



Hi,

The instructions to download the ETSI reference codec can be found here:  http://tetra.osmocom.org/trac/wiki/Speech_Codec although I never got it working completely. There is an output stream but there is no audio data in it. Just (random?) clicks and pops.

Cheers,

Pepijn

Op 23 sep. 2011, om 15:20 heeft Dieter Spaar het volgende geschreven:

Hello Bigsat,
>
>On Fri, 23 Sep 2011 13:49:43 +0200, "Bigsat" <bigsat at gmail.com> wrote:
>
>
>>
>Is it possible to release some part of the code necessary to decode 
>>
>Tetra voice or give some explaination of Gsmtap usage ?
>>
>
>>
>Just in case, I have sent my "proof of concept" modification
>for voice decoding to the authors of Osmocom TETRA for proper
>integration a while ago. As far as I am aware the current
>source code should be able to decode voice or at least contain
>the instructions how to do it (the ETSI reference codec is most
>certainly not included for copyright reasons).
>
>Best regards,
> Dieter
>-- 
>Dieter Spaar, Germany                           spaar at mirider.augusta.de
>
>

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Hello,

Regarding questions how to use the ETSI codec: It consists of two steps,
"cdecoder" and "sdecoder". The ouput of "sdecoder" is raw sound in signed
16-Bit PCM format with 8000 samples/second. For example Audacity can play
it without problems.

(And no, its no "magic", it just requires to read a few comment lines in
the source code of the codec).

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                          spaar at mirider.augusta.de


Hello,

I have tried this and ran the sdecoder and cdecoder whitout any problems. But when I open the result in Audacity (8000Hz / 16-bit PCM) I just hear clicks and pops and a long beep every now and then.

I have read the ETSI document regarding the codec, so no magics :)

But do you actually hear output from a real life network? Because I tried the examples attached to the ETSI document regarding the testing of the codec. They work very nicely, but no luck on real life networks so far. (yes, no encryption)

Regards,

Pepijn
Op 24 sep. 2011, om 14:28 heeft Dieter Spaar het volgende geschreven:

> Hello,
> 
> Regarding questions how to use the ETSI codec: It consists of two steps,
> "cdecoder" and "sdecoder". The ouput of "sdecoder" is raw sound in signed
> 16-Bit PCM format with 8000 samples/second. For example Audacity can play
> it without problems.
> 
> (And no, its no "magic", it just requires to read a few comment lines in
> the source code of the codec).
> 
> Best regards,
>  Dieter
> -- 
> Dieter Spaar, Germany                          spaar at mirider.augusta.de
> 





Apart from the codec patches for ETSI codec i cant find any other voice
decoding source code in osmocom-tetra trunk. Neither seems to have
entered you in the AUTHORS file.

FAQ on the site says:

"Can your software actually play the voice signal?

Currently we have no support for that. However, a yet unreleased proof-of-concept version exists."


Why this secrecy for publishing source to decode unencrypted networks?.
Have osmocom been threatened by the tetra manufacturers? 
Would damage sysmocom commercial interests

> > 
> 
> Just in case, I have sent my "proof of concept" modification
> for voice decoding to the authors of Osmocom TETRA for proper
> integration a while ago. As far as I am aware the current
> source code should be able to decode voice or at least contain
> the instructions how to do it (the ETSI reference codec is most
> certainly not included for copyright reasons).
> 
> Best regards,
>   Dieter
> -- 
> Dieter Spaar, Germany                          spaar at mirider.augusta.de

-- 
<>



On 09/24/2011 03:37 PM, Mccauley wrote:

> Why this secrecy for publishing source to decode unencrypted networks?.
> Have osmocom been threatened by the tetra manufacturers? 
> Would damage sysmocom commercial interests

Hi,

sysmocom is building a GSM BTS, right now there is no interest in doing
something commercially with tetra.

We can not integrate the ETSI audio code in our (A)GPL software, the result
would not be freely distributable. From my side I was mostly interested in the
signalling part, or if time would permit try transmitting.

So if you either find a legal way to include the ETSI code at build time, or
preferable write a GPL compatible audio decoder, I think we would be happy to
include it in the git repository.

cheers
    holger


Hello Pepijn,

On Sat, 24 Sep 2011 15:49:37 +0200, "Pepijn van den Berkhof" <vandenberkhof.pepijn at gmail.com> wrote:
> 
> But do you actually hear output from a real life network? Because I
> tried the examples attached to the ETSI document regarding the testing
> of the codec. They work very nicely, but no luck on real life networks
> so far. (yes, no encryption)

I know that others have used the current code to decode speech, maybe
someone can confirm it.

I haven't worked with the code for a while and so can't confirm it,
but it has worked for me in the past.

Maybe I find the time to try it within the next few weeks, if possible
I will also try to provide a sample capture from a test TETRA network
so everyone can try the sample. "Test TETRA Network" means from a
network under our control run in a faraday cage so that there are
no legal issues providing the capture.

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                          spaar at mirider.augusta.de



is that could help us for voice decoding : ?

http://www.joys99.com/d-4784.html

-- 


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