[linux-dvb] Re: New UK DVB-T channels testing

[Holger Waechtler <holger@convergence.de>]

Klaus Schmidinger wrote:
>>
>>Why don't you want to use 32-bit frequencies?
> 
> 
> Because I would like to use the "natural" values, and those are typically values
> like 12345 MHz for DVB-S, and 567 MHz for DVB-C and DVB-T. The "center" frequencies
> are apparently given as integer MHz values (even though the DVB standard allows
> 32 bit values). See Lauri Pesonens most recent posting:

I don't see anything "natural" in MHz values. I would never like to 
castrate programs to tune to some frequencies without serious reason...

The center frequencies directly depend on the base frequencies for 
UHF/VHF bands. These bands were in past specified differently in 
different countries, just an example:

    Band 5 in Australia:                    139.125 MHz
    Band 5 in South Africa:                 222.150 MHz
    Band K5 in French Overseas Territories: 223.450 MHz
    Band 5 in Indonesia:                    221.150 MHz
    Band 5 in Chile:                        123.000 MHz
    Band 5 in China:                        161.250 MHz
    Band 5 in CCIR assignment:              253.050 MHz

Even if these frequencies are not specified by the DVB consortium nobody 
forbids a provider to transmit in these channel ranges, and I'm sure 
some of them will do so, just to make the DVB channels fit better 
between the old analog transmission bands.


>   The NIT reports frequencies like 283000000Hz when I'm using 282750000Hz
>   with VDR. So The NIT reports the 'official' freqs without the offset.
>   Offsets are -250kHz for QAM_128 freqs and -125kHz for QAM_64 freqs.
 >
> Therefore it should be sufficient to store the "center frequency" and allow for
> an offset handling, which in case of DVB-T could be done by an 'O' parameter
> (note that it's the character between 'N' and 'P', not the number 'zero'), and 
> in case of DVB-C a table of offsets for the various QAM modes should do the trick.

Are you sure that these offsets are related to the used modulation? What 
makes you sure of that?

Holger



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