This post will attempt to provide a list of things that I have done in an attempt to improve the picture quality on my Hauppauge PVR-150. Hopefully it'll help anyone else who has this card and feels that the picture quality is somehow lacking and save them the time of crawling through the net and this forum looking for things to try.
My setup:
KnoppMyth R5E50
Hauppague PVR-150 (with the TCL M2523_5N_E tuner)
PIII 750 Mhz w/ 384mb RAM (no stuttering whatsoever, cpu utilization ~75%)
nVidia FX5200 w/ S-video to composite adapter plugged into TV.
27" CRT with normal analog cable.
Background:
Overall, my picture quality is quite good. In fact, it's better than it used to be. For some reason, my A/V system added snow to a whole bunch of channels and all of this static/snow is gone when I run the signal through my mythbox and then to the TV. That said, on those channels that are clear, I gradually began to notice a difference in quality. I've got a coax splitter set up so that I could quickly switch between the original analog signal plugged into the TV and the signal coming through the mythbox (technically speaking, the other output from the splitter goes to my VCR (which I use to tune) and a composite video cable goes to my TV from the VCR). Tuning to the same channel, I clearly noticed a difference in quality.
The difference is most notable when watching cartoons (Futurama or the Simpsons). After getting tipped off that something was wrong, I looked at other channels and noticed that they all looked a bit off. It's nothing obvious, but you get the feeling that something is wrong after watching for more than a few minutes. I settled on using the weather channel for all of my comparisons because the screen stays constant for long enough that you can really compare the two, and there is a good amount of color and text on the screen.
The Problem:
The picture doesn't look as vibrant/the colors are washed out/not quite right. There is NO static whatsoever. In more detail:
The colors themselves appear faded. Whereas on the weather channel, the color of the numbers for the temperatures superimposed on the map appear bright and vibrant, when watched through Myth they appear somewhat dull and faded. If you look at people's faces, on TV the skin color looks "pinkish" whereas through the MythBox it looks slightly orange/red.
When the people are standing in front of a blue screen on which a weather map is projected, they clearly look superimposed on normal television. Through the Mythbox though, they appear more blended and seem to fade into the background. Boundaries are not as sharp. One could say the picture looks slightly blurry; it feels like it lacks some detail/definition. When text is on the screen, it also appears slightly more blurry through the MythBox.
Of course, it's very difficult to describe what I'm seeing without posting some side-by-side screenshots. However, a digital camera would probably introduce it's own artifacts. The closest I can come to describing the difference is here (stolen from someone else who noticed the same thing):
http://capnbry.net/~bmayland/fi/pvr150/pvr150-250.jpg. See how the Sci-fi logo is kind of blurry/faded/not as sharp or vibrant as that from the 250? Sufficce it to say, things don't look quite right, although they look very good and very close to normal TV.
Things to try:
While searching the web, here are some things I came across. Because MythTV, KnoppyMyth, and ivtv are all under such rapid development, I would ignore any post more than 6 months old. It's incredibly frustrating to read someone who appears to have the same problem as you, then see someone post a patch/fix, then see the original poster jump for joy at their problems being solved, only to realize that this patch was incorporated into the drivers over 3 months ago. That said, here are some current suggestions floating around. If you have the problem described above, hopefully some of these things will help:
1. Read this page:
http://www.knoppmythwiki.org/index.php? ... lityIssues
It's pretty general and I didn't find it all that useful, but it does list a number of things worth trying:
a. Try changing both your display resolution (mine is set to 800x600 and changing it to 640x480 had no effect) and your capture resolution (I tried 720x480 with no effect). See the first post by hverkuil for some information why changing the capture resolution affects PVR-150 cards
http://www.gossamer-threads.com/lists/mythtv/dev/247305 or the post by ethernut
http://mysettopbox.tv/phpBB2/viewtopic.php?t=13097 (this is also in the general upgrade hints/hazards for R5E50 page, number 3 under known issues). I didn't notice much of a difference, though.
b. Use the nvidia-settings tool. This tool is a biggie for owners of nVidia cards like me. Try fiddling with the overlay settings and the TV-out settings. In particular, the flicker filter on the TV-out page is supposed to improve image quality. I definitely noticed a difference when using it, but calling it an improvement is questionable. I noticed that lowering the setting made the image a little sharper at the expense of making the text harder to read (all of the text would all of a sudden have these rainbow patterns start flowing through them). Raising the setting made everything slighly fuzzy, but the text became MUCH easier to read (especially on the program guide). No matter what I set the flicker filter to, though, text never looked as good as on normal TV and everthing still looked slightly blurry/fuzzy.
c. Use the Xv picture controls. You have to activate these first in mythtv setup->tv settings->play back->2nd page (Use Xv picture conrols). Then, while watching live TV, press the "f" key on the keyboard to cycle through settings to change and press the left/right arrow key to change them. I played with the hue a lot in an attempt to make the skin color line up better with normal TV but I never could get it quite right. People either looked too blue, too green, or too red. They never had that same "pink" flesh tone that they did on my TV.
2. Some people think this temporal filter setting change works wonders:
http://mysettopbox.tv/phpBB2/viewtopic.php?t=13257. I didn't notice any difference with it, though.
3. In the general updade hints/hazards for R5E50 page (
http://mysettopbox.tv/phpBB2/viewtopic.php?t=13108), number 4 under known issues looked particularly promising. I had to "touch /etc/modprobe.conf" before that script worked, but it made no difference for me after I tried it and rebooted to make sure the new module options took effect. This fix appears to be for static, though, so since I don't have any I'm not surprised it didn't do anything.
4. Try using Bob2 deinterlacing and XvMC for the MPEG2 decoder (under setup->tv settings->playback). Although it did slighly decrease my CPU usage (from 75% to 60%, it didn't do anything for problem with my colors/sharpness). It also made my OSD black and white, but there's a fix for that here:
http://www.mythtv.org/wiki/index.php/XvMC. If you're going to use XvMC, make sure you've fixed the bug in number 10 in the known issues on the general updade hints/hazard for R5E50 page.
5.
http://mythtv.org/pipermail/mythtv-user ... 17393.html hints at tweaking the registers on the capture card itself to improve quality (here too:
http://capnbry.net/~bmayland/fi/pvr150). Something ommited from that page is that you first have to modprobe i2c_dev in order for the cx25840ctl program to work. I tried tweaking all of the values suggested there and the difference was very slight.
If you have any more suggestions, please feel free to post them. Maybe this thread can become the one stop picture quality post for users of the PVR-150. I know that would have been my life over the past week a lot easier.
At this point, I've basically given up on my PVR-150. Maybe this is just as good as it gets and I'm too much of a perfectionist. I just wish the picture quality coming out of my MthBox looked as good as what's plugged straight into my TV. I may yet cave in and buy a PVR-250, but that seems like a gamble to me since picture quality appears to be dependent on so many factors that there's no telling whether a 250 would be better or worse than what I have now. Since everything is working, maybe I should be grateful.
The incredible feature set of MythTV (I can't imagine living without Mythweb now), probably means I'll just deal with the inferior picture quality.