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Newbie needs help w/ TV Out quality
http://forum.linhes.org/viewtopic.php?f=2&t=6805		 Page 1 of 1
Author:  Lev [ Sun Nov 06, 2005 7:17 pm ]
Post subject:  Newbie needs help w/ TV Out quality
Hi folks-

I've been reading up for a few weeks and finally built my new KnoppMyth box this weekend. I'm a complete Linux newbie, and amazingly I managed to get the basics up and running this wekend. A testament to the great work that went into KnoppMyth!

I've got my Nvidia 5200 outputting to a PAL tv, but I've been fiddling with everything to get the quality better - it's just nowhere near as clear as regular TV. I've especially tried different modelines at native PAL resolution of 720x576 in my XF86Config-4 file, and confirmed that this resolution is working in the logs, but it doesn't help much. I'm using an S-Video from the graphics card to the TV.

Any other tips anyone can suggest? Is there a way to detect the best modeline for my TV?

Thanks,
Lev.
Author:  tjc [ Sun Nov 06, 2005 7:48 pm ]
Post subject: 
For modelines visit the modeline generator at source forge. http://xtiming.sourceforge.net/cgi-bin/xtiming.pl You'll need to know the appropriate sync ranges for a PAL TV which don't have handy... Searching for "PAL modeline" here should turn up a variety of options...

For other display tune ups try using the nvidia-settings utility.
Author:  pkscout [ Sun Nov 06, 2005 8:50 pm ]
Post subject: 
tjc wrote:
For modelines visit the modeline generator at source forge. http://xtiming.sourceforge.net/cgi-bin/xtiming.pl You'll need to know the appropriate sync ranges for a PAL TV which don't have handy... Searching for "PAL modeline" here should turn up a variety of options...


OK, this has very little to do with the actual thread, but I did want to say how nice that modeline generator is. I just used it to generate one for my Panasonic ED plasma and it actually made sense. Now I just have to get my Myth box built so I can try it. :D
Author:  Greg Frost [ Sun Nov 06, 2005 9:53 pm ]
Post subject: 
Have you tried adding this to your XF86Config-4 file?
Code:
Options "TVStandard" "PAL-B"
(or whatever the pal standard in your region is).
Author:  Lev [ Mon Nov 07, 2005 9:09 am ]
Post subject: 
Thanks, tjc, for the modeline generator. That's a great tool. It seemed to produce a modeline that works pretty well. This is what I'm using:

Code:
"720x576@60i"  12.58 720 752 808 840 576 587 593 605 interlace


I do have the XF86Config-4 set to "PAL-B."

After a lot of futzing, the thing that REALLY helped improve picture quality was using an S-Video > Composite adapter to connect to the TV's
Scart plug rather than just plugging the S-Video direclty to the Scart plug. It really improved things, which surprises me because I thought keeping it as S-Video would be better quality.

However, I still have some quality issues with the feed from the antenna:

(1) When the first tuner ("video0") on the PVR500 card gets a good signal on a particular channel, the card's other tuner ("video1") gets a much worse signal. And vice versa.

I have the two tuners ("video0" and "video1" respectively) on the PVR500 set up like this:

Code:
video0>Tuner0>antenna
video1>Tuner0>antenna


Does that look correct? I assume Tuner0 is the coaxial input. Should each of the card's tuners be set to use a different input?

(2) I have one channel that doesn't come in very well. Is there a way to fine-tune the channel apart from trial & error in the channel setup?

I'm sure I'll have more questions since I'm so new at this, but I'm first just trying to get the quality settings OK so I can watch TV.

Thanks!
Lev.
Author:  tjc [ Mon Nov 07, 2005 7:27 pm ]
Post subject: 
Quote:
(1) When the first tuner ("video0") on the PVR500 card gets a good signal on a particular channel, the card's other tuner ("video1") gets a much worse signal. And vice versa.

Try flipping your splitter around and see if the problem reverses itself. A lot of coax signal splitters are asymertical with one path having a much lower signal loss that the other(s). This may even be printed right on the splitter. If thats the problem you can buy a symetrical one relatively cheaply...
Author:  Lev [ Tue Nov 08, 2005 4:54 am ]
Post subject: 
tjc wrote:
Try flipping your splitter around and see if the problem reverses itself. A lot of coax signal splitters are asymertical with one path having a much lower signal loss that the other(s). This may even be printed right on the splitter. If thats the problem you can buy a symetrical one relatively cheaply...


Ah, but I'm not using a splitter; I have the coax going into Tuner0 on the PVR500, feeding both /dev/video0 and /dev/video1. It's not always the same tuner that gets the weak single; sometimes one and sometimes the other.

Thanks,
Lev.
Author:  tjc [ Tue Nov 08, 2005 7:11 pm ]
Post subject: 
What's the other coax connector on the card for, an FM antenna?
Author:  Lev [ Wed Nov 09, 2005 5:07 am ]
Post subject: 
tjc wrote:
What's the other coax connector on the card for, an FM antenna?


Yeah, that's right. A lot of good that does!
Author:  Lev [ Sat Nov 12, 2005 6:14 am ]
Post subject: 
I wanted to give people an update on how I solved this problem on my PVR500:

Quote:
(1) When the first tuner ("video0") on the PVR500 card gets a good signal on a particular channel, the card's other tuner ("video1") gets a much worse signal. And vice versa.


After days of head-scratching and reading these forums, I came across this thread: http://mysettopbox.tv/phpBB2/viewtopic.php?t=5749; in particular, MrFahrenheit's mention of the file /etc/init.d/set_ivtv_params.

It turns out that one of the tuners on the PVR500 was properly being set to the PAL resolution of 720x576 I have in my recording profiles as well as my display settings in the XF86Config-4 file, but the PVR500's other tuner was defaulting to 720x480 (NTSC default, I think). Thus a blurry picture.

So, in the set_ivtv_params, I changed this line to have the right resolution:
Code:
$IVTVCTL -d /dev/video$f -f width=720,height=576


And I saw that the set_ivtv_params refers to the config files in /etc/sysconfig/ivtv/cfg-0 and /etc/sysconfig/ivtv/cfg-1 (one file for each of the PVR500's tuners). Everything in those files was commented out, so the set_ivtv_params file was just using default settings. So:

change /etc/sysconfig/ivtv/cfg-0 so:
Code:
IVTV_TUNER='0'
IVTV_TYPE='PAL'

and for /etc/sysconfig/ivtv/cfg-1:
Code:
ITVTV_TUNER='1'
IVTV_TYPE='PAL'


And that did the trick - now a clear picture with both of the tuners. :)

Regarding problem (2) above - bad reception on 1 particular channel - I get a lousy signal on that channel, and it seemed that the PVR500 was just making it worse. I basically got that channel to be as good as it is direclty to the TV by using good quality shielded coax cables - never underestimate the value of a good cable!

Now on to the next challenges, like downloading program listings, controlling set top box, and remote.
Lev.
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