[mythtv-users] tuning two-card systems ?

Maarten mythtv at ultratux.org
Thu Oct 21 23:07:27 UTC 2004

On Saturday 16 October 2004 01:36, Michael T. Dean wrote:
> On 10/15/2004 04:25 PM, Maarten wrote:
> >I notice that my two bttv cards are not what you'd call exactly in sync,
> > where the tuners are concerned.  If one card gives good picture, the
> > other is just slightly off-channel so the colors are too pronounced, or I
> > get stripes and other interference.

> I'm having the same symptoms on a multi-PVR-250MCE system.  I think it's
> from the splitter reducing the signal strength, but I'm still trying to
> find a good solution.  It seems the $5, 4-way splitter from a certain
> supercenter in my area is not high-quality and not recommended for cable
> TV.  Coupled with the fact that the cable feeding the house is split
> with another 4-way splitter and that the cables are using twist-on
> F-connectors, I think the signal strength is way too low by the time it
> gets to the card.

Well...  I should kiss the ground you walk on because, YES, this was exactly 
what was causing my tuning card differences !! (incredible as it may sound)

After a lot of thinking and hesitating I went out and did what I should've 
done months ago; I bought me a highly expensive Hirschmann antenna-amplifier, 
some good plugs of same brand and a high quality shielded splitter.  The bad 
news: that cost me 120 euros.  The good news: It solved ALL my problems !!
My two cards seem right in sync now, and have (much) better picture to boot.
In fact so much so that I now decreased the bitrate from 3000 to 2600 *and* 
disabled both HQ+4MV, yet the picture is still better and sharper than it was 
before (!).  This really is an eyeopener...  

Obviously, the added benefits are plenty: Since much less CPU power is needed, 
(no more HQ+4MV) I could decrease the overclocking on my 2600+ slightly and 
still keep just under 100% CPU when recording two shows, watching one and 
having a raid5 (parity calculations!) array work underneath it all.  
And due to the lower bitrate I get less disk-usage per show to boot !

For anyone using (especially) bttv cards: I urge you to invest in a good 
amplifier and/or good splitters.  Don't get fooled by the fact that your VCRs 
and TVs do not suffer from the (bad) signal; do NOT assume that if the TV 
works fine the cards will too.  Apparently the bttv cards are much more 
demanding than a TV when it comes to signal quality and -level.   
In my case it solved more problems than I would've thought remotely possible.

Thanks Mike, and others, who eventually set me on the right track.

( Ehm, maybe this oughtta go in the wiki or docs...? )


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