[linux-dvb] question on frontend API

[Tim Lapawa <tim@lapawa.net>]

Hello list,

at the moment I try to scan the frequencies on my cable for channels. I am not sure if my broadcaster sends digital channels anymore. They want to use some frequencies for backward channels and therefore they moved almost every channel to another frequency.

I began to write a C program which steps through all the frequencies and looks for a valid signal. Without demuxing, filtering or something like that. Just looking for the signal. At the moment I do not understand how the looking for a valid signal should be done.

First I check the status of the Frontend:
A ioctl on  /dev/ost/frontend with FE_READ_STATUS gives me this information:
Frontend status:
  FE_HAS_POWER          : TRUE
  FE_HAS_SIGNAL         : FALSE
  FE_SPEKTRUM_INV       : FALSE
  FE_HAS_LOCK           : FALSE
  FE_TUNER_HAS_LOCK     : FALSE

Now I  give him this first FrontendParameter with  FE_SET_FRONTEND:
  FEParameters.Frequency = 410000000;
  FEParameters.Inversion = INVERSION_AUTO;
  FEParameters.u.qam.SymbolRate = 6900000;
  FEParameters.u.qam.FEC_inner = FEC_AUTO;
  FEParameters.u.qam.QAM = QAM_64;

The card gives me a event back, after 2 or three seconds. 
Type is: FE_FAILURE_EV failure event, we couldn't tune
Frontend status at failure:
  FE_HAS_POWER          : FALSE
  FE_HAS_SIGNAL         : FALSE
  FE_SPEKTRUM_INV       : FALSE
  FE_HAS_LOCK           : FALSE
The included status information is not encouragingly.

I doe not see, why the tuning failed. Because of what? Failed it just because of a missing signal? Or is something wrong with my card? Must the tuner be locked to a frequency to result in a succeded tune operation? And why is the FE_HAS_POWER flag FALSE? Does the card go to sleep when he can not tune a channel?

Unfortunately the API pdf does not give a hint on that. It is not in a actual manner and does not sescribe the coherences.  I will switch to the header files :)

I hope someone can give the results a meaning.

Greetings
	Tim


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