[mythtv-users] HDTV Blues - Any ideas?

Brian Wood beww at beww.org
Mon Mar 20 00:35:51 UTC 2006


On Mar 19, 2006, at 4:59 PM, Chris Lynch wrote:

> On 3/19/06, Steven Adeff <adeffs.mythtv at gmail.com> wrote:
> > 1 - Watching LiveTV or recording a channel will not always work.   
> It will go
> > to a black screen and then come back to the main menu.  With  
> LiveTV trying
> > over and over will eventually work.  When it's recording a show  
> you have no
> > way of knowing if it's actually recording.  This one has put me  
> in the hurt
> > locker with my wife on Myth :)
>
> Set the DCT connection setting to Broadcast and 200 or 400mbps. power
> down the computer and the cable box and repower both, this should
> solve the issue. as well, if channel tuning doesn't work use 6200ch
> (in the contrib folder) for channel changing and try the "new" method
> (theres a switch to enable it).
>
> I'll give this a shot.  Thanks for the pointer - there's not a lot  
> of info out there for troubleshooting.
>
> > 2 - Pixellation every 10 seconds or so.  It lasts for about 1 - 2  
> seconds
> > and it is part of the recording stream so it's not a playback  
> issue as best
> > as I can tell.  I have verified that running my DCT-6200 direct  
> to the TV
> > does NOT exhibit the pixellation, so I don't think it's related  
> to weak
> > signal (I've even plugged in an amplifier to boost the signal  
> strength).
>
> This is a firewire kernel driver problem. Some firewire chipsets
> aren't as bad as others, but its a problem with the kernel and
> partially Myth,  both of which are being worked on.
>
> Interesting - I've tried my motherboard one (VIA chipset) and the  
> one on my Audigy 2.  Is there a recommendation anyone has to what  
> chipset or even a specific board to buy?  I'll buy whatever works  
> at this point :)
>

Especially with Via-based motherboards you need to be very careful of  
PCI Latency settings. I was getting glitches in recordings if I tried  
to watch LiveTV at the same time, even with just 1 SD recording.

Re-setting the latencies, the system could then make 3 recordings  
while watching LiveTV without a glitch. Check the WiKi at:

http://www.mythtv.org/wiki/index.php/PCI_Latency

Also, some older Via boards had DMA problems that caused trouble for  
IVTV, there is some info on that on the IVTV site.

I'm not saying any of this is directly related to your problem(s),  
but it never hurts to have everything optimized. I'd try a latency  
setting of b0 hex for your IDE controller first. If your F/W  
controller is capable of transferring data faster than the IDE  
subsystem can write it to the diskyou would get your (2) symptom.
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