[linux-dvb] Glitches with Terratec Cinergy 1200 DVB-T?

Hartmut Hackmann hartmut.hackmann at t-online.de
Tue Jul 26 00:23:49 CEST 2005


Hi, Andrew

> 
> Actually I reverted my change because it made things worse on a different 
> machine. I've been getting no errors at all now, so I don't have anything 
> else to change.
> 
> What problems have you been getting?
> 
It looks like there is quite a number of uncorrected errors in the transport
stream (but not constantly). The reception conditions here are poor: not
much energy and short echoes in the signal (what i remember from analog days)
So at most channels, i have a quite high raw ber which is not really
surprising.
But i see that my settop box, which also has the tda10046 channel decoder,
does a significantly better job. This convinces me that there is room
for improvement.
You might know that i already spent some effort on the driver for this
chip. But there i concentrated on the initialization and on supporting
more tuners. I hardly looked at the tuning algorithm yet and i suspect
this is not perfect.
I guess that you might have played with the parameter for the IF frequency.
Best working for me so far is the Medion card with the FMD1216 tuner.
While i tried to optimize it a bit, i found that i get the lowest raw
ber when i set the IF frequency to 36.125MHz. This cannot be correct
since the tuner is not even able to provide this IF frequency. What I
suspect is that the crystal of the channel decoder is quite far off.
The chip seems to be able to lock with a high frequency offset but does
this with some performance degradation.
I don't know what is precisely in this IC, but this is what i observed so
far. If you find something similar, this gives a good starting point
for optimization.

Best regards
    Hartmut




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