[linux-dvb] DVB-T Full Spectrum Frequencies Scan

P. van Gaans w3ird_n3rd at gmx.net
Wed Aug 22 17:28:51 CEST 2007


On 08/22/2007 04:57 PM, Frederic CAND wrote:
> Hi everyone,
> 
> I'm having some troubles trying to perform a dvb-t frequencies scan 
> without a scan file.
> Does anyone know if a software (or even an algorithm i could write in C) 
> exist to do so ?
> My idea was to scan frequencies using all combinations of DTT 
> parameters. This is a first problem because it makes a lot of 
> possibilities. The second problem is that I don't know on which 
> frequency I should start my scanning, nor the step to use between to 
> frequencies.
> 
> I thought to parse the Terrestrial Delivery System descriptor in the 
> NIT, but it appears that some countries do not fill correctly this 
> descriptor (particularly the "Frequency" field). So it's useless.
> 
> I'm looking for a universal method that do not need a scan file to be 
> specified to automate everything. As STBs can do that i though that we 
> could do that programatically.
> 
> If anyone has a clue, please help :'(
> 
> 

Some time ago I made an "all-UHF" scanfile, but it was rejected because 
of the autoscan feature available with some DVB-T cards. However, far 
from all DVB-T cards support autoscan, and in that case you simply need 
all-UHF. But it was rejected anyway, because every card *should* support 
autoscan. But they don't. So you have a problem. Well anyway. If you 
want all-UHF, just ask and I'll look it up and send it to you. all-UHF 
only scans channel 21-69, it does not scan frequencies in between like 
channel 21,5 (21,5 would be 478Mhz). But in most countries such 
frequencies are not used anyway. For guard interval and other settings 
it uses "auto", supported by every card that I've tried.



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