[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.


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