[linux-dvb] Needs to get the SNR value in dB, with dvbtune

["Samuel Torton" <samuel@ncslab.com>]

Hello,


I'm using a DVB card Hauppauge WinTV Nova-S on a linux Debian box, and I
developed a software in order to get SNR, Viterbi, lock, status and
strength signal values. For that, I used drivers and get inspired from
dvbtune (dvbtools) software source code.

- I use the DVB drivers found here:
  http://www.linuxtv.org/download/dvb/
  --> OK, that works

- I use the DVBTUNE software:
  http://www.linuxstb.org/dvbtune/index.shtml
  --> OK, that works, but I still have some problems to get the right
  values (units) for the following values:
      - SNR (especially) ;
      - Signal Strength ;
      - Viterbi ;
      - etc...

In order to get the SNR value, I used the following lines in the
"tune.c" source code:
      ------------------------------------------
      strength=0;
      ioctl(fd_frontend,FE_READ_SNR,&strength);
      fprintf(stderr,"SNR: %d\n",strength);
      ------------------------------------------

My questions are :
- What's the unit of the value FE_READ_SNR to be displayed ?
  Usually, a big number is displayed, but I want to display this value
  in dB, so is there any math formulae to apply, in order to get
  this value in dB ?
  If yes, what is it ? (*)
- Same questions for FE_READ_BER, FE_READ_SIGNAL_STRENGTH

(*) For example, if I install this DVB card on a Windows box, with
WinTV software tools on Windows, I can see the SNR level in a color bar,
and the value expressed in dB, such as in the example provided in this
image: http://www.hauppauge.fr/sup/cap/nexus2.jpg


I read the following documentation:
http://www.linuxtv.org/download/dvb/linux-dvb-api-1.0.0-pre1.pdf
but I didn't find answers to my questions.

Am I on the right mailing-list to ask for these informations ?
Otherwise, where could I post ?

Thanks a lot for your help.

--
Samuel Torton
http://www.ncslab.com 




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