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Old January 4th, 2008, 01:37 PM   #1
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Why do I get fluid motion on LCD TV but jerky on PC monitor ?

When I play back my footage from the camera on a 19" LCD Tv, my pans are 100% fluid. When I capture the footage on my PC, then play back the Mpeg file (using any Media Player) my pans are a little jerky, not too bad but its there. Its the same on my Laptop.

Why is this ?

Is this normal, or do I have a problem. Is there a minimum PC spec for HD capture and playback.

I have a pretty good spec PC...

Intel CoreT 2 Duo E6400 Dual Core 2.13GHz
2GB RAM
320MB Nvidia Geforce 8800 GTS
320GB Serial ATA Hard Drive with 16MB buffer
21" Viewsonic VP2130B LCD Monitor

Any advice welcome

Mark
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Old January 4th, 2008, 02:16 PM   #2
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Most likely your original footage is interlaced and your LCD TV is displaying it as interlaced.

On your PC, unless you have deliberately dropped the monitor's refresh rate to 60Hz interlaced then the video will be displayed one entire frame at a time instead of two fields sequentially. Hence, you wil perceive some "stutter" during pans/fast motion. It is simply because each interlaced field should be displayed every 1/59.94 seconds but media player etc show both fields simultaneously every 1/29.97 seconds. i.e., every second field is displayed too early.
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Old January 4th, 2008, 02:17 PM   #3
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Are you shooting interlaced video?

If so, probably what you are seeing is:
1. On the TV the video is being displayed correctly as interlaced. Everything is smooth.

2. The computer monitors are progressive. For the video to be displayed correctly on the computer, it needs to be de-interlaced. (Video that is intended for the web, for example, is deinterlaced.)
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Old January 4th, 2008, 02:45 PM   #4
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Great thanks for the prompt reply's guy's. I thought it maybe something to do with the progressive scan and interlacing, I shoot in 50i. I usually save my final output for PC playback using WMV and 50fps de-interlace mode. This works well and much better than a 25fps video, but it still has the same slight jerkyness as the original, I would of thought it would of improved things.

Should I have any setting on my Hard drive turned on or off. I usually have Wright Caching turned on, should I turn it off. What about the Paging File options ?

Thanks again,

Mark
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Old January 4th, 2008, 05:57 PM   #5
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I should have spotted you are in Wales so my 59.94 and 29.97 values should of course be 50 and 25.

Regretfully, the ability to match the refresh rate of a PC monitor to PAL material is all but impossible unless you have a graphics card that can support 50Hz.

Whatever refresh rate your monitor is running at that is the rate that the video has to be displayed, too. So if your refresh rate is 85Hz, 50i or 25p cannot be matched hence there will always be some jerkiness. If you can select a refresh rate for your monitor that is an exactly multiple of the video field/frame rate (i.e., 100Hz or 75Hz) the jerkiness will be notably reduced.

Hard drive issues etc aren't at play here. They would manifest themselves as occasional jerks rather than consistent ones.
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Old January 4th, 2008, 06:19 PM   #6
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Thanks John, that does indeed explain things, I appreciate the help.

Mark
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Old January 4th, 2008, 06:56 PM   #7
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John is correct in what he said. The Windows DirectShow filter uses the hardware clock on the sound card to make the frame rate. It's not the most stable clock in the PC system. And even when you get the frame rate matched to the frame rate of the monitor, the two are not synchronous.

There is freeware app out there called ReClock. It's sort of a virtual tracking downcoverter. The software synchronizes the PC clock to the monitor, smoothing out the playback and making it fluid.
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Old January 5th, 2008, 03:36 AM   #8
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Thanks Tom.

I did a little experimenting last night. As my Monitor is set at 1600x1200 @ 60Hz, I decided to save a video at 30fps instead of 25fps or 50fps. It was much smoother. Now because my original was shot at 50i, I should be saving at 25fps...right ? So what am I actually doing when saving the final output to 30fps, and is this ok.

Sorry for even more questions,

Mark.
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Old January 5th, 2008, 08:46 AM   #9
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One more thing.

My graphics card has two display plugs installed. Is there a way I could use a seperate monitor for my video's. I won't need both monitors on at the same time, but the other monitor I have has a resolution of 1280x1024. Will this cause a problem considering my main monitor uses 1600x1200. Is there a way I can just switch between displays off the same graphics card.

Thanks again,

Mark
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Old January 5th, 2008, 12:51 PM   #10
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If your card is like mine, you can set the secondary output to be separate from the main one. I have a video monitor (i.e., NTSC/PAL) connected via S-video to the card's secondary output. The configuration software lets me choose true NTSC (720 x 480 x 59.94i) or PAL (720 x 576 x 50i). When I play DV format AVI files in a window on the secondary display it is indistiguishable from sending the DV file to an external DV deck and viewing on the monitor that way.

My card is an nVidia 7600GS. I use it on XP Pro and Vista. The XP Pro configuration software is much more flexible and permits many options for the secondary output though it seems to be a bit of an art to get it to overscan - the default is underscanned.
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Old January 5th, 2008, 12:52 PM   #11
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Once you plug in second monitor, your Video Card software set up utility should help you select optimal monitor settings for each monitor individually. You can also do it my right clicking on any empty spot on the desktop, and go into setting. Initially, the second monitor port may be grayed out, and you will need to activate it in the settings, picking either to extend desktop to that second monitor, or to mirror whats on the first monitor. I set it on extend. Then, in Vegas, I use the second monitor to preview, by selecting external on the preview monitor setting. Just remember, this second monitor can take up a lot of resources in the editing process, and depending on the level of preview, you can get some pretty choppy video. I actually have to preview at a pretty low quality level, because my system is on the low side of adequate.
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Old January 5th, 2008, 01:56 PM   #12
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Thanks again John and Chris.

Well I had a little play around today. I set up a second monitor with a resolution of 1280x1024 @ 75Hz refresh rate. The playback is now much smoother, just as good as the LCD tv, and the good thing is, is I can just swap displays when I'm running video. I had a little trouble because I found out that when using two monitors, you have to have them both connected with the same plug...ie DVI or VGA, you can't have one and the other.

Thanks for all the input, its been a good lesson learnt.

Mark
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Old January 6th, 2008, 02:42 PM   #13
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Well I'm back again.

I've looked into a second LCD monitor that supports 75hz. Its being a little harder than I thought it would be. It seems that most of the latest monitors (LCD) are running at 60hz. I've read up from a few websites regarding refresh rates on LCD's and it sounds as if changing the refresh rate doesn't do a great deal like it does on a CRT. I've taken a look at the Re-clock site, but I'm a little worried that I may end up causing more harm than good.

Can anyone give me some advice on either a good lcd monitor that can handle 75hz at its native resolution or if there's anyone that has had success with re-clock. I'm running Windows Vista and Windows Media Player 11, although I also use KM Player.

Thanks again, it looks like I may of hit a brick wall.

Mark
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Old January 6th, 2008, 04:29 PM   #14
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I used ReClock back in 2004 to sometime in 2005. It's a definite improvement but it and your video players have to be configured properly. I stopped using it when I migrated to 1080, which simply overwhelmed my PC of the day with or without ReClock. It worked great on 720p though. With my current PC, I would still have jumpy stuttering video on 1080 with or without ReClock. It just doesn't have the horsepower, and I have better playback options, HD DVD players and PS3 connected to Pioneer Elite 1080p plasma monitors.

I still recommend ReClock, but it's not a panacea. PC's aren't great playback platforms usually.
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Old January 7th, 2008, 12:00 AM   #15
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I'm using PAL Pana GS400 frame footage. The occasional stutters in Vegas VMSP 8c preview are still with me after I've tried everything. It's all PAL DV Widescreen with an ATI FireGl 5200 card with a zillion display refresh rates available, currently set at 25hz interlaced. Fw 800. CPU around 40% video usage. Renders prove OK in Win Media Player.

Are there any programs that'll tell me where the blockage might be? Going to try ReClock, apart from its default and recommendations settings what others should I look for. Thx.
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