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Picture Tuning - Tweeking 101
http://forum.linhes.org/viewtopic.php?f=6&t=1039		 Page 1 of 3
Author:  adrianbc [ Mon Mar 22, 2004 7:49 am ]
Post subject:  Picture Tuning - Tweeking 101
Can anybody suggest ways to improve the recording/playback quality of my mythbox from cable. I have a PVR 250 so I'm not sure what options are available to me such as codecs, filters etc... Also I don't really know what my system can handle (below). I have been doing tests at High Quality which for me is DVD, 720x480 a bit rate of 5600. Still I have motion blur, strange banding at times in areas of high contrast. My goal is to approximate Tivo's quality i.e. reproduce broadcast.

It looks like I have finally gotten my mythbox to record. I have got a working sound card on the machine or a decent video card so I've been SFTPing my .nuv files to my windows box to see them. Since I'm using the PVR card, I just rename the files to .mpg . So far, the video quality is pretty good but there is definate motion blur. I would just like to make sure that I have the recording down pat before moving on to the remote xbox frontend.

On my windows box I'm able to watch DVDs with out having any strange motion blur, artifacts etc... So I think the problem is on the myth end. However, if this is a interlacing issue as some have suggested, how can I fix this?

BTW I replaced all my cabling with really short runs of good shielded cable - from what I can tell (n00b that I am) , this is an encoding/decoding issue.


Some of the particulars:

- Athlon 1.3 Ghz
- 640 MB of RAM
- Hauppauge PVR 250

Thanks,

I just need to get a good solid demo for my wife so I can justify the second xbox, modchip, etc...

:)

Adrian
Author:  Xsecrets [ Mon Mar 22, 2004 9:22 am ]
Post subject: 
well going to the higher res isn't helping anything for analog tv. It doesn't have that high of a res. As for the motion blur and banding I don't really know if you can get rid of it. I still have it with mine on very fast action scenes, but changing the jitter reduction and interlacing options under playback may help. just filp one on then both then the other etc to see which will give you the best picture.
Author:  Grooby [ Mon Mar 22, 2004 3:00 pm ]
Post subject: 
you can try to add "kerneldeint,denoise3d" under your setup -> tv -> playback -> custom filter

and uncheck the "deinterlace" checkbox. See if that helps...

(I am writing this from memory so someone correct me if I am off here)
Author:  adrianbc [ Mon Mar 22, 2004 3:13 pm ]
Post subject: 
I gave those filters a shot in my playback setup. No effect.

Thanks, anyhow
Author:  Grooby [ Mon Mar 22, 2004 3:18 pm ]
Post subject: 
also are you using nvidia gpu graphic card? I have a little problem w/ my mx 440 when I have overscan on.....
Author:  Xsecrets [ Mon Mar 22, 2004 4:38 pm ]
Post subject: 
just curious grooby where did you find out about those filters? I've never seen a list of available filters and their purpose. I would love to know where one is.
Author:  Grooby [ Mon Mar 22, 2004 4:53 pm ]
Post subject: 
http://www.mythtv.org/docs/mythtv-HOWTO-10.html
Author:  stylin16 [ Thu Mar 25, 2004 8:13 pm ]
Post subject: 
I'm having the same motion blur problem. It's kind of a combination blur and possibly dropped frames. It really annoys my wife and me. You can especially see the problem on Fox News with the scrolling line at the bottom. Could XVMC be causing this problem? If so, how can I turn it off? I need some serious guru help here because I am so darn close to selling my Tivo and running with this. I am also using a PVR250 with a GeForce4MX440.
Author:  cesman [ Thu Mar 25, 2004 8:21 pm ]
Post subject: 
I don't know if XvMC could be the problem... Did you install the deb w/ XvMC?
dpkg -l | grep xvmc
Author:  stylin16 [ Thu Mar 25, 2004 9:49 pm ]
Post subject: 
Yes, I did install it with XVMC and I think you are right that that is not the problem. I increased the bit rate to 9000 and it helped the motion problem quite a bit, but not completely. When there is quick motion, the interlacing seems to tear a little bit...like I only see half the lines in the moving area. It is really strange. I'm using the ivtv drivers that came with R4V2. Should I maybe change those? Is this normal?
Author:  Xsecrets [ Thu Mar 25, 2004 10:21 pm ]
Post subject: 
I've always had that on my pvr250 no mater what I tried, It's not too bad unless it is really fast motion like sports.
Author:  adrianbc [ Fri Mar 26, 2004 6:40 am ]
Post subject: 
Is it actually possible to get TV-like image quality out a (computer) video
monitor? Or is there something about these monitors that makes this
impossible.

y plan was to move onto setting up the Xbox (connected to a TV) as a front
end once things were pretty good on the server. At this point, I'm wondering
if the problems I'm having are inherent to CRT monitors or if something
still isn't right with my recordings.

For the past several days I have been working on getting my myth box up and
running. So far, I think that I am pretty happy with the backend setup.
However, when I try to watch recordings on my CRT monitor, they seem a
slightly fuzzy and the colors or a bit off. Occasionally I'll see some
motion related banding or artifacts I've tried playing around with
different filters on the playback end: kerneldeint (or just the regular
deinterlace video setting), quickdnr, denoise3d etc...with or without
parameters. There are little differences but it still doesn't look like TV.

TV seems pretty good despite the fairly low resolution.

I have a PVR 250 with the latest drivers. I'm pretty secure with the setup
on this end. As far
as I know, there really isn't a whole lot I can try on this end in terms of
filtering since this uses hardware encoding. My recording profile is
supposed to be DVD quality at 720x480(I know, this exceeds the broadcast
output) and 12000-16000 bit rates. Still the picture looks blah on my
monitor despite the 5 gig per hour file size.

On the output side (which is the same machine), I'm using a Nvidia FX 5200
with 128 MB connected to a 19in Viewsonic CRT Monitor. I've got the latest
nvidia drivers. I'm running my display at 800x600 which I understand to be
myth stock. As mentioned above, I have tried to use different several
different filters in different combinations. I have experimented with and
without interlacing (kernel which my proc supports and regular). I have also
FTPd the large mpeg files to windows systems just to see if this was a
problem with my nvidia setup.

I have an Athlon 1.3 GHz and 640 MB of RAM which should be adequate to the
task.

Any insight would be helpful. All I want to do is match Tivo and broadcast
quality.

Adrian
Author:  Xsecrets [ Fri Mar 26, 2004 8:20 am ]
Post subject: 
I know this sucks to say, but if you are looking for output that looks like tv and it is the slight interlacing effect that really drives you batty then you probably need to go back to a software encoding card. They do not have this problem.
Author:  adrianbc [ Fri Mar 26, 2004 8:32 am ]
Post subject: 
wow - that does suck - I thought that I was doing something wrong on the output end. I guess that this means that an XBOX output to TV won't help.

I really only got the PVR because it was my understanding that this would work well. Several posts claim that they meet or exceed broadcast quality with PVR250/350.

Is it possible to not use the hardware encoding on the PVR 250 and to do this software encoding?

:(

Adrian
Author:  Xsecrets [ Fri Mar 26, 2004 10:01 am ]
Post subject: 
nope you can't use a pvr250 and do software encoding. The pvr cards do give you a crisper image that is quite noticeable, however I have never been able to get the interlacing artifacts to go away in very high speed action. I can imagine it being a problem for a sports fan, but I really don't notice it that much just watching shows.
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