[linux-dvb] DVB file formats

Marcus Metzler mocm at mocm.de
Fri Jun 17 09:34:44 CEST 2005


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

    Andreas> Hi, On Fri, 2005-06-17 at 00:10 +0100, Andrew de Quincey
    Andreas> wrote:
    >> The first thing that springs to my mind is something like the
    >> following:
    >> 
    >> DVBS: ((frequency / (symbolrate/1000)) << 1) | polarisation
    >> DVBT: (frequency / bandwidth) DVBC: (frequency / symbolrate)

    Andreas> AFAIK there can not be more than one multiplex one
    Andreas> frequency except if the polarization differs. That makes
    Andreas> me think that the divisions are unnecessary. Instead I'd
    Andreas> like to see the orbital position in there for DVB-S
    Andreas> somehow like that:

    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.

Marcus

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