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PostPosted: Sun Sep 13, 2009 9:39 pm 
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Joined: Wed Jan 10, 2007 10:59 am
Posts: 25
Hi all,

I noticed something interesting after installing a fresh R6 today (I did update with pacman -Syu and that did not change anything). I seem to have a weird interlacing/progressive problem between my mythbox and tv (I think). I was watching the nfl on nbc tonight and found that the static graphic they have on the bottom of the screen (with people's names, scores, etc) was just the tiniest bit jittery - it moves up and down ever so slightly. I don't seem to notice it with people in the rest of the screen, but perhaps it's because they are not staying in the exact same spot (ie, whether the whole screen is shaking or just the graphic part - I would expect it is the whole thing).

So I tried switching the video scan option (near bottom of menu that appears while watching a show and you press 'm') from "detect" to "progressive". I think this stopped the jittering from occurring - it just seemed like the static graphic was staying put. However, it changed the rest of the screen such that any decent movement of people started doing a wierd horizontal line effect - definately some sort of interlacing effect - like the people were split into lines. Switching the video scan to "Interlaced (Normal)" looked the same as the "detect" setting. Switching it to "Interlaced (Reversed)" really caused bad interlacing effect type things.

I still consider myself a newbie w.r.t. linux, so I am looking for any options or programs to run or try out to see if there are any configuration things I might be able to change to get a better picture. I did find nvidia-settings - all I know of to look at in there is that the video is set for 1280x720 and 60hz. Any other settings to try in there, inside of the myth setup, Linhes setup or otherwise?

And of course, here's the details of my setup. I have a Samsung DLP tv (HLP5063WX - native resolution of 720p) hooked up via dvi out to dvi input on the tv (nvidia is able to detect the tv type and the tv thinks it is getting the 1280x720@60hz). My computer is a basic dragon 2 setup - 2 tuner Airstar HD5000 and Nvidia 7600 GS, Core 2 Duo, 2GB ram. Oh yeah, it is an OTA HD system tuned to KXAN in Austin for the example above. Thanks in advance for any help or suggestions.


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PostPosted: Mon Sep 14, 2009 3:22 am 
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Joined: Mon May 10, 2004 8:08 pm
Posts: 1891
Location: Adelaide, Australia
The up and down jitteryness would be a result of using the bob deinterlacer. It is a simple deinterlacer which gains the benefit of the higher field rate that interlaced video offers for fast motion scenes, but not the higher resolution that can be achieved for still shots (you get the up and down jitter).

By switching to progressive you would have disabled the deinterlacer which is not what you want because you will see all of the interlacing artecatcts like someone scraped a comb horizontally across the picture.

If you have the horsepower there are other deinterlacers available. yadif 2x is probably the best, but needs a fair bit of grunt particularly for deinterlacing 1080i. Another option is Greedy x2 which I think works better than Bob.

I use Greedy 2x for HD and yadif 2x for SD.

You can configure which deinterlacer is used in the playback settings.


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PostPosted: Mon Sep 14, 2009 10:02 pm 
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Joined: Wed Jan 10, 2007 10:59 am
Posts: 25
Awesome Greg, that's exactly what I was looking for - thank you so much - and your descriptions of what I was seeing were spot-on. I did find that the yadif 2x needed too much power (I ran a top in xterm window while watching tv in the background). Here are the various %cpus (Core 2 duo, hence the above 100% - not sure if it is good to be running above that or not):

yadif 2x - 125->130 (unwatchable - only getting every few frames)
yadif - 100->104 (seemed ok)
greedy high motion 2x - 100->115 (above 100 but very watchable, rather smooth)
greedy high motion - 80->86 (the 2x version seemed smoother/cleaner)
kernal - 40-48 (seemed decent)
linear blend - 35-45 (about same as kernal)
one field - 38-42 (about same as linear/kernal)
bob 2x - 38-42 (has the jittering that I originally wrote about)

Just for completeness, here's where I was doing to change the setting using R6.
Main Myth Menu -> Service Menu -> MythTV Configuration -> Setup -> TV Settings -> Playback
Then Next twice so on Playback Profiles (3/9)
Mine is set on CPU++ (I think default for me), arrow to the "Edit" button next to the 'if rez > 0 0 -> ffmpeg & XVideo', hit enter
Then Next once to get to the second screen where it lists Primary Deinterlacer. Change as needed, then arrow to Finish and hit enter
Then keep hitting enter until back to the TV Setting screen to save the changes.

And as a follow up, are there any details anywhere about the various decoder or video renderer choices in the 1st of the edit screen settings for the playback profile. I generally leave things at default settings, but would changing any of those help to get my cpu usage down some? Should I be concerned that it's running above 100% using the greedy 2x (which looks to be giving me the best picture)?

Again, thanks so much for help - it's gonna keep me from going crazy while watching certain programs (or getting a headache) :)


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