[linux-dvb] Re: [vdr] Re: dxr3/vdr problem

[Holger Waechtler <holger@convergence.de>]

Malcolm Caldwell wrote:
> I have a few questions about the dvb drivers/devices that perhaps
> someone can answer.
>
> When receiving from one of the transponders on asiasat2 I have no
> problems at at all.  While running vdr and also running dvbtune -m I
> see:
> ...
> Signal=53116, Verror=0, SNR=43860dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=53427, Verror=0, SNR=43815dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=52821, Verror=0, SNR=43836dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=53090, Verror=0, SNR=43758dB, BlockErrors=0, (S|L|C|V|SY|)
>
> On another transponder I see:
> Signal=41268, Verror=65357, SNR=37605dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=41267, Verror=65291, SNR=37608dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40916, Verror=65494, SNR=37554dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40953, Verror=65381, SNR=37479dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40660, Verror=65349, SNR=37548dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40977, Verror=65315, SNR=37539dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40976, Verror=65434, SNR=37560dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40665, Verror=65419, SNR=37575dB, BlockErrors=0, (S|L|C|V|SY|)
> Signal=40946, Verror=65478, SNR=37641dB, BlockErrors=0, (S|L|C|V|SY|)
>
> This second transponder always gives high levels of Verror.  For parts
> of the day the Verror will be around 20000 and the service seems to work
> and my dxr3 won't freeze.  At other times it is up around 65000 and
> things don't work and the dxr3 will eventually freeze (requiring either
> a vdr restart or sometimes a machine restart)
>
> My questions:
> 1.  Whis is this Verror?
the Viterbi bit error rate.

> What is its units? 
absolute bit errors between two status ioctls.


> It understand it is related
> to BER but how?  
Block Errors - or better Uncorrected Block Error Count - is the number 
of MPEG packets that have not been corrected by the forward error 
correction unit. These get visible as real artifacts in video or audio.


> I understand it is a 16bit number so it would seem my
> values are high.
yes. Try to adjust your satellite dish a little bit better or 
check+improve your cable installation.


> 2.  Why the difference between these two services?  I thought it may be
> symbol rate (the first is 20400 while the second is 28125).  
some transponders are transmitted at higher power rates than others. For 
the weak ones you might need to adjust your antenna a bit more precise 
or maybe you even need a better LNB/bigger satellite dish.


> I have been
> assuming that my problems are RF related but is this perhaps some kind
> of problem due to a high load on a low end machine?
In some setups the RF emissions or instable power supplies of your PC 
might cause problems, but usually the satellite installation is the main 
source of troubles.

Holger



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