[linux-dvb] DVB file formats

Marcus Metzler mocm at mocm.de
Fri Jun 17 11:55:37 CEST 2005


>>>>> "Andreas" == Andreas Oberritter <obi at linuxtv.org> writes:

    Andreas> On Fri, 2005-06-17 at 09:34 +0200, Marcus Metzler wrote:
    Andreas> (orbital_position << 22) | (polarization << 20) |
    Andreas> frequency_mhz
    >> I looked for some examples in my current dvbrc which is for 5
    >> orbital positions. With 207 transponders I found 32 cases of
    >> the same TSID involving 117 of the transponders, i.e. between 3
    >> aand 4 transponders per TSID. If you exclude the cases where
    >> you have different orbital positions to distinguish between the
    >> transponders you still have 28 cases with 108 transponders. If
    >> you use the polarisation to distinguish the transponders you
    >> get 29 cases (15 for V with 49 transponders and 14 for H with
    >> 41 transponders) and still 100 transponders.  If you take the
    >> first 4 digits of the frequency, all these remaining cases can
    >> be resolved.  So a combination of transport ID, orbital
    >> position and frequency should be enough. Polarisation does not
    >> really help much.

    Andreas> So how do you want to distinguish the following two
    Andreas> transponders without including the polarization? How does
    Andreas> the bogus transport stream ID help?  Can you give an
    Andreas> example where my proposal creates the same ID for two
    Andreas> different multiplexes?

    Andreas> 1.0W 11.654 GHz H, TSID 0x0001 ONID 0x0001 1.0W 11.654
    Andreas> GHz V, TSID 0x0001 ONID 0x0001

The TSID is really not useful for distinguishing the
transponders. From what I can see your example is the only case where
the polarisation is needed. I don't think there are many satellites
that use the same frequency with two polarisation unless they service
two distinct areas. Unfortunately I can only see the footprint for one
of those transponders at satcodx and I can't tune them. 

Anyway, I was just looking at the statistics I get from the channels I
got.

Looking at your example it seems that all eventualities have to be
taken into account, so that polarisation is needed and maybe even
some other data. 


Marcus

-- 
/--------------------------------------------------------------------\
| Dr. Marcus O.C. Metzler        |                                   |
| mocm at metzlerbros.de            | http://www.metzlerbros.de/        |
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