My video playback isn't quite perfect and I'm hoping to get some help. I've done various searches, both in this forum and others, and the results have helped me make a lot of progress, but I still have a bit of a problem when playing back sdef (720x480i) recordings. When playing back CNN, which has the "ticker" going across the bottom of the screen, I see 15-25 seconds of perfectly smooth ticker playback, followed by 1-3 seconds of mild "jerkyness". This pattern repeats on an on-going basis. This is the best result I've achieved to date -- not sure yet what happens with my 720p recordings as I haven't watched any 720p recordings yet with my latest changes.

Any ideas on how to get rid of this final "problem" would be appreciated. I would also be interested in knowing if anyone else is getting better results playing 480i over VGA to an HDTV. Thanks!

Marc

Same key configuration notes:

0. Running Knoppmyth R5A30.2.

1. P4-2.8ghz with hyper threading enabled; ECS motherboard with SIS chipset.

2. Nvidia FX-5200 based video card with latest Nvidia driver (8756)

3. Using VGA output to Samsung 50" DLP TV whose native resolution is 1280x720p.

3. I play back both 480i and 720p recordings at 1280x720p. XVMC disabled; "use libmpeg2" selected. Note that I have tried doing to playback 480i recordings at 640x480, but it actually looks worse than if I do playback at 720p.

4. Video output filters for 480i recordings are "+kerneldeint,denoise3d".

5. I have EDID enabled in my XF86Config-4 file. EDID did not work properly for me with the 6629 driver, but it does work properly with the 8756 driver.

6. I am using "option TVstandard HD720" in my XF86Config-4 file. This results in the automatic creation of a "1280x720" modeline that yields better results than any others I have tried.

Prior 720p modelines I have tried include:

Hello

You might take at look at this post. I think it will give you some insight to your problem...

http://mysettopbox.tv/phpBB2/viewtopic.php?t=9696

unfortunately your tv's standard resolution is 720p. 1080i gives you much better playback on 480i video without having to resort to any filters. Also note that 64x480 is not 480i that is 480p (well approx.) I have not been able to get a true 480i modeline working with the nvidia drivers.

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Xsecrets

I get noticably smoother playback when I turn OFF the option that runs the frontend at "root" privilege. I also do better with sync via OpenGL turned OFF. My system runs 1080i at all times -- it's the only modeline my TV will accept over VGA. I let myth change the resolution of my 720p shows to match my TV modeline on the fly.

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Marc: under pre-R5B7 versions of MythTV/KnoppMyth, I would see playback problems like that with SD recordings, when I had forgotten to turn off XvMC after watching some HD recordings. Playback was fine but would glitch every so often, maybe every 15-25 seconds like you're describing.

I'd turn XvMC off and the problem would go away.

I didn't see you mention whether you've turned XvMC on or not in Playback Options, but if so, try it.

Try Bob 2x deinterlacing with OpenGL vsync enabled. That gives me super smooth video for exactly the situation you describe.

Thanks!

Andrew Lynch

Thanks everyone for the rapid replies -- very much appreciated! I've sifted through all the feedback and tried a bunch of experiments. What I found is that selecting "Enable OpenGL vertical sync for timing" has improved things dramatically. As i watch the ticker very closely, I can see a very occasional, very minor "glitch". I have some other recordings where playback looks much better in scenes that used to look bad -- mostly scenes that involved a lot of panning. So it's looking a lot better, thought still not perfect.

It amazes me how different configurations seem to solve the problem for some people but cause more problems for others. Some examples:

1. Xsecrets sees best results playing back 480i recordings at 1080i. My HDTV will accept 1080i input even thought it's native resolution is 720p. Unfortunately for me, 480i does not look good on my HDTV when played back at 1080i. On the other hand, 1080i recordings look great when played back with my HDTV set to 1080i.

2. lynchaj sees great results with Box 2x deinterlacing. Bob 2x does not look good on my setup. Having said this, we do share the common result that enabling OpenGL vsync improves things.

My guess is that the differing experineces have to do with differing driver versions, different behaviors on our various HDTVs and other configuration differences.

Again thanks for all the quick feedback and if other ideas come to mind please let me know and I'll give them a shot!

Ceenvee703 -- I don't use XVMC -- gives me too many problems, but thanks for the suggestion of turning it off!

RacerX -- Thanks for the pointer but I had already read that post -- that's where I picked up the idea of using the "option TVstandard HD720p".

Liv2Cod -- I don't use the "playback in realtime" option, but thanks for the warning. I've avoided using this option as I am concerned that it essentially gives a higher priority to "playback" then to "recording", but my feeling is that recording should have the higher priority.

Marc

Make sure your vertical overscan percentage is 0%. That made a huge difference with my setup. When it was non zero, the screen looked awful.

Thanks!

Andrew Lynch

I've already set all vertical overscan/underscan settings to 0/0%.

Quick question -- My HDTV's manual says it's vertical refresh rate is 60hz. My understanding is that the recordings are all transmitted at 59.94hz. Should my modeline be one that resolves to a 60hz or 59.94hz vertical refresh rate? Stated another way, should my modeline's vertical refresh rate match the refresh rate of the HDTV or the refresh rate of the material being played back? Also, does it make sense that my HDTV would implement a vertical referesh rate of 60hz given that everything is transmited at 59.94hz?

Thanks!

Marc

I've tried modelines for both 60 and 59.94 Hz on mine and I don't see any difference.

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besides my guess is that tv companies just added 0.04hz to make things easy on the consumer. Standard tv's claim a 60hz refresh as well, but us techies know that NTSC is actually sent at 59.94hz. The general masses like nice round figures, so the marketing dept gives it to them. well right up until we start talking about price of course.

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Xsecrets

I reviewed a series of test scenes last night and I've come to the conclusion that what I have is actually as good as it gets. While I was able to identify very occasional, very brief and very minor imperfections during playback, what I also found was that TIVO actually demonstrates a simliar level of "imperfection" in video playback. My wife also reviewed the results and came to the same conclusion. So to summerize:

1. Playback of 720p recordings at 1280x720 is flawless.
2. Playback of 480i recordings at 1280x720 using kerneldeint is very good -- slightly better overall results than on my series 1 TIVO.
3. Playback of 1080i recordings at 1920x1080i is TBD -- I will know more after we watch ER at the end of the week .

Thanks again for all the help!

Marc