[mythtv] [S2API] modulation system and roll-off questions

[Janne Grunau]

On Thursday 30 October 2008 09:47:20 wagabunda wrote:
>
> I am finishing writing patch which provides support for DVB-S2
> by the new S2API. It works transponder edition, a full scan
> and scan the transponder with 8PSK transponders.

Thanks this is very welcome.

> I have added a fields "Roll-off" and "Modulation system" to the
> screen "transport edit". I also modified
> SatelliteDeliverySystemDescriptor, DTVMultiplex and DVBChannel, of
> course.
>
> I have a few questions:
>
> - For which release to public this patch, release-0-21-fixes or trunk
> ? I have yet to clear, so I modify it a little bit also.

Please make the diff against trunk

> - Roll-off require new fields in table dtv_multiplex. If roll-off is
> always equal 0.35 in in commercial broadcasting, may set it on a
> constant value ? I read that 0.20 and 0.25 are used only to the
> professional broadcast.

"predictions are hard, especially about the future"

they might be used for standard broadcast, or someone wants to use 
mythtv with a professional broadcast system. We should save all 
parameters from the DVB-S delivery system descriptor into the 
dvb_multiplex table.

> - Modulation system require new fields in table dtv_multiplex, too.
> If QPSK == DVB-S and 8PSK == DVB-S2 and QPSK with DVB-S2 is
> impossible, this field is not required and code is simpled. Is it
> combination with QPSK and DVB-S2 delivery is possible?

According to ETSI EN 300468 V1.8.1 only 16-QAM can't be used with DVB-S2 
so we should save the delivery system too. This might be useful for 
DVB-C and  DVB-T too.

Janne