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PostPosted: Sun Jul 02, 2006 3:55 pm Reply with quote
flostog
 
Joined: 14 Jul 2005
Posts: 9




Well I captured a file while in X-windows and then I captured a file in run-level 3. The file captured while in X was corrupted, while the file captured in run-level 3 played back without a hitch - no errors.

So do you think a different - non-nvidia - <a style='text-decoration: none; border-bottom: 3px double;' href="http://www.serverlogic3.com/lm/rtl3.asp?si=22&k=video%20card" onmouseover="window.status='video card'; return true;" onmouseout="window.status=''; return true;">video card</a> could solve the problem? Any suggestions?

Ron
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PostPosted: Sun Jul 02, 2006 11:00 pm Reply with quote
xyzzy
 
Joined: 12 Feb 2006
Posts: 225




You might changing the driver from "nvidia" to "nv" in the xorg.conf file. I find that I do not have any problems with QAM reception with the nv driver.

Something that I have seen reports of working for other people is to upgrade to a better quality power supply. A video card can use lots of power, and I think that this is creating the noise in the power supply that messes up reception.

I also have an old bt848 analog tv card with an audio output straight from the tuner, and if I put headphones into it I can quite clearly hear X activity. So obviously there is noise created by X activity that is getting into the analog signal. It seems reasonable that this noise would mess up the demodulation of digital TV transmissions.
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PostPosted: Thu Jul 06, 2006 8:18 am Reply with quote
flostog
 
Joined: 14 Jul 2005
Posts: 9




Well I ran a test where I booted to run-level 3 and had the mythbackend record 3 NTSC streams and 2 HD streams simultaneously. From a software perspective Myth performed as it should have (I finally got the ivtv and v4l-dvb modules to play together - I forgot to check a box in my kernel config - I used the built-in drivers and added your patch manually).

The NTSC streams were perfect, but the HD streams suffered the same data corruption I see when I'm running X. I suspect that the noise caused by the other cards were getting into the mix. Based on this test, running the nv driver might help if I am only capturing an HD stream and nothing else, but as soon as I engage the other hardware, I'm going to get corruption.

I'm using a good power supply (or I least I think it is) its a SeaSonic-430. Should be plently big enough to handle the setup that I have. I still got data corruption when I took out everything except a single PCHDTV-3000 and the nvidia cards. I know 430W is plenty for that setup.

I have ordered an Air2PC HD5000 and will see if it makes a difference. I would have tried PCHDTV's new card, but its too new and there is not enough feedback yet.

Thanks for the help. BTW - Your ATSCScan is a great little program - thanks.
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PostPosted: Thu Jul 13, 2006 11:39 pm Reply with quote
flostog
 
Joined: 14 Jul 2005
Posts: 9




Well the verdict is in....................

The PCHDTV-3000 sucks at QAM 256. It is extremely sucseptible to outside interference. I just installed the Airstar HD5000 and I have QAM256 playing without a hitch. This board (HD5000) however has been a pain in the a$$ to install. At first the PCI bus couldn't even see it. I'm still in thge process of getting the whole system back together after ripping out cards,

On a high note, I suspect that PCHDTVs new 5500 will probably deal with QAM-256 much better than the 3000 due to the new frontend tuner (I think its very similar (newer generation ???) to the one in the HD5000)

Ron
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PostPosted: Wed Jul 19, 2006 7:25 pm Reply with quote
ubulid00
 
Joined: 13 Nov 2004
Posts: 4




Has anyone tryed the PCHDTV-5500 for QAM256 support compared to the PCHDTV-3000? I'm getting marginal Comcast cable reception so every DB could help...
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HD3000 QAM Not locking
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