[linux-dvb] CAM inserted/used reduces signal and SNR ?

Manu Abraham abraham.manu at gmail.com
Tue Nov 27 20:34:56 CET 2007


Luc Brosens wrote:
> 
> Manu Abraham wrote:
>> Luc Brosens wrote:
>>
>>> Manu,
>>>
>>> your guess is correct, under W2K no tuning problems. The scrambled channels tune in an instance, now and then there are some artifacts though. But
>>> tuning works !
>>>
>>> so my hardware setup works, now how to find that 'tenderness' in the driver ? You think that the tuning-part of the drivers (that would be the
>>> STV0299-stuff wouldn't it ?)
>> It can be the STV0299 + the tuner on it. What tuner do you have on the card ? Maybe 
>> it is bad tuner programming, before looking elsewhere. Tuners wrongly programmed 
>> cause such weird issues, one can say.
>>
>>> if somebody can set me off in the right direction, I'll get it solved
>>>
>>> the Windows TV-viewer that came with the cards reports a signal of 95%, even for scrambled channels : another indication that tuning could be done a
>>> bit better ?
>>>
>>> Luc
>>>
>> Manu
>>
> 
> Manu,
> 
> it's a KNCOne TV-Station DVB-S
> on it, I can see a STV02998 and a SAA7146AH
> the tuner chip is obscured by a cover plate
> I've prepared a little page with some pictures and the dmesg, lsmod and lspci info :
> 
> http://www.bsc-bvba.be/persoonlijk/kncone.html
> 
> even though I bought it as a TV-Station, and that's what it says on the box, it is taken to be a TV-Star
> if I change the PCI-id-table in budget_av.c and make it a TV-Station (SUBID_DVBS_KNC1), I get "timeout waiting for end of xfer" from the SAA
> 

You are trying the latest changes in the tree, ie the topmost changes, 
IIRC Oliver had some fixes which fixed some IRQ issues.

> the budget-av coding for the TV-Star seems to suggest the tuner is a SD1878, which is confirmed by the label on the cover plate (you can read it on
> the pictures of the front of the card)
> 
> I'll go and read the SD1878 coding ...

try this change:

in dvb-pll.c: http://linuxtv.org/hg/v4l-dvb/file/85f583ec85d6/linux/drivers/media/dvb/frontends/dvb-pll.c

The following lines:

      473 		{ 1250000, 500, 0xc4, 0x00},
      474 		{ 1550000, 500, 0xc4, 0x40},
      475 		{ 2050000, 500, 0xc4, 0x80},
      476 		{ 2150000, 500, 0xc4, 0xc0},


change this to make it look like this:

{ 1250000, 500, 0xc4, 0xc0},
{ 1450000, 500, 0xc4, 0xc0},
{ 2050000, 500, 0xc4, 0xc0},
{ 2150000, 500, 0xc4, 0xc0},

This is bad but, check whether you see any difference.

Manu



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