Johannes Stezenbach wrote:
On Sat, May 13, 2006, Manu Abraham wrote:
Johannes Stezenbach wrote:
The way I read the standard, the ACM return channel
could be a telephone line or DSL/internet to the playout center.
The demod hw would handle ACM receiption automatically, and an
application would monitor signal quality and send commands back
to the transmitter to change modulation and fec until it gets
max throughput at good quality.
Well, as i said, from the specs, again 6.1 has a nice picture how it is
done too .. I did _not_ say that the demod is having DVB-RCS capabilities.
In any case, whatever mode is used the specs _says_ MODCOD is used. IMHO
MODCOD is necessary, eliminating modulation + coderate.
I didn't say MODCOD is unnecessary.
I did say it is unnecessary *in the Linux DVB API*.
Okay, How do you expect the apps to talk to the API for MODCOD ?
According to your suggestion, all DVB-S2 drivers will need to encode
MODCOD from modulation and coderates. The application does decode the
MODCOD and send it to the driver.
Maybe the drivers should try to guess delivery system as well then .. ;-)
This *is* indeed an ugly solution. Moreover what i believed was that
which is common to all drivers and part of the specifications is part of
the API.
Because the API uses what it gets from the
satellite_delivery_descriptor, which is FEC and modulation
in two seperate fields.
Specs says MODCOD as an entity, not 2 different fields. The specs do not
say MODCOD is Modulation + Coderate eventhough it indeed *is*. Nor does
the devices either. Reading the device registers itself gibves you the
MODCOD, just like what you read FEC information.
Even a quick glance on the specs will prove it.
And we might provide MATYPE for informational purposes,
but decoding it is left to the application. You could
put the code to decode it into dvb-apps/lib/ somewhere.
Not yet reached there. Will do some utils as soon as it is finished.
Manu
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