[linux-dvb] Weak signal

Christian Kaenzig chrismoll at chrismoll.homelinux.org
Wed Sep 7 13:47:19 CEST 2005


Le Mardi, 6 Septembre 2005 15:43, Damien Bally a écrit :
> Hello

Hi.

> I'm experiencing a rather weak signal when using tzap, though my dvb-t
> reception seems to be OK.
> Here are the figures :
>
> signal : 0043
> snr :     fff
> ber:     0
> unc:     0

Of what I have read on this list, it seems these numbers can mean different 
things depending on the driver and the dvb card. Values returned by the 
hardware seems not to be very well documented (in most cases, I guess).

> As far as I'm not mistaken, the signal is an integer coded in hexa, so it
> means  67 out of 65535, which is very very low. The README indicates 0x800
> and above as a correct value.
>
> Is 0x0043 a reliable figure or a bug in tzap ?

Here are the values I get :

status 1f | signal 7676 | snr f2f2 | ber 00195000 | unc 00000000 | FE_HAS_LOCK

My card is a Terratec Cinergy 1200 DVB-C. With this card, the signal and snr 
always give two identical bytes. For the signal value, lower means a better 
signal. For the snr, the higher the better.

The ber acts a little crazy with this card. It can vary between the above 
value and somthing like 20 with no apparent reason, but it only gets updated 
like twice per minute, or so.

So I think the only really important value is unc, which are the number of 
blocks that could not be corrected by error correction algorithms and thus 
directly affect the quality of the output stream. For a perfect picture and 
sound, you need 0 here.

So, IMHO, you shouldn't worry much about the other values as long as there are 
no uncorrected blocks.

Regards,

Christian



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