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Old October 18th, 2009, 09:08 AM   #1
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Motion blur problem (continues) - advice needed.

Hi All,

Apologies for further posting on this topic but I've still not got to the bottom of this annoying issue despite some very useful responses from which I learned a lot!

The problem is persistent motion blur and jitter when HDV footage (from a Canon XH-A1) is imported into my MacBook Pro (4Gb RAM, 2.6 GHz Intel Core 2 Duo). I've also tried it on a new tower G5 with no difference so don't think its a memory / processor issue. The original footage looks fine - smooth with no blur or jittering - and if I print it back to tape it also looks fine. I tried de-interlacing using Compressor (and other apps) and though this helps to some degree (and does a good job of de-interlacing as I use it for DV stuff very effectively) the basic problem remains. I also tried various players / editors to play the clip (QT, VLC, FCP6) and monitors, but again it makes no difference.

The links below show the clips (shot in Nice, France) - the first is the original clip for reference and second the de-interlaced version. It was shot with a fast shutter to capture the fine detail of movement but don't see how this would make a difference and as I said on tape it looks good, if with that fast shutter look:


As it only looks good on tape I can't show you how it should look but does anyone now how to fix this issue? I can always use tape as my mastering format but should that be necessary? Do I have unrealistic expectations of HDV on a computer? Why does it look fine on tape?

Thank you.
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Old October 18th, 2009, 09:32 AM   #2
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I'm a bit late to the party on this as I haven't seen your original post. Your problem is clearly showing up on Vimeo. Where else does it show up? When you "print to tape" are you converting to DV or staying HDV?

What I can see is that the problem stems from handling interlaced footage. Vimeo only likes deinterlaced footage. In fact, contemporary LCD, DLP and Plasma displays are natively progressive scanning. I think the reason you're seeing the double ghost images rather than interlace "mice teeth" is that Vimeo doesn't deal with frames and mashes both fields into a frame. In fact, Vimeo has long recommended that you deinterlace the file you want to upload.

If you are having this issue show up in other output formats, pay attention to how you are dealing with fields. Understand the technical details of the desired delivery format and make sure the fields are handled correctly during the conversion.
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Old October 18th, 2009, 09:49 AM   #3
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Thanks Tripp but it's not a Vimeo problem as though it doesn't look quite so good on Vimeo the basic problem is the same whatever I use to view it on the Mac. On tape it looks fine in the original and printed back to tape (as HDV). The 2 clips show the original (top) and de-interlaced versions to show that I don't think it is an interlacing issue.

When I import I tried QT (raw footage - no field settings available) and FCP. I've tried messing around with fields in FCP but nothing seems to solve it. I assume it is top field first which I think is correct for HDV. I should say it is shot at 1080x50i.
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Old October 18th, 2009, 10:03 AM   #4
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Btw I should have made it clear that the ghosting issue in the interlaced clip is not a Vimeo issue (it is there as soon as it is imported into the Mac and NOT in the original) and when viewed full screen the teeth are also present. These are both removed by de-interlacing (bottom clip) but the motion blur / jittering remains.

A helpful forum member pointed out that when played from tape my LCD monitor detects it is interlaced footage and adjusts accordingly which it cannot do when receiving signals from a window in the computer. My overall point is that I think the interlacing issue is a red herring and the blur is caused by something else but I could be wrong!
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Old October 18th, 2009, 03:48 PM   #5
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Could it be the refresh rate of your monitor that is giving the ghosting effect, maybe when you play straight from tape the computer changes it's refresh rate to match a TV signal and displays at 50i whereas it uses maybe 60P or 75P for editing.
I now just do a frame based output for viewing on a computer and except that jittery look of 25P. For home playback on a TV I use a Western Digital HD Media player at 50i with excellent results.
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Old October 18th, 2009, 09:47 PM   #6
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You didn't answer the questions I asked so it will be hard to offer any further insight.

To be clear, I'm not inferring that the problem is with Vimeo. It may be with the transcoded version of the video that you uploaded. If you are creating a version for playback on any computer in any format or for playback on an LCD, Plasma or DLP TV, you should deinterlace.

Read my previous comments thoroughly. I'm not sure that you are getting my points.
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Old October 20th, 2009, 06:49 AM   #7
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Sorry Trip but I'm not sure what point I didn't address - the problem shows up whenever I play the video from computer either on the computer screen or via an attached LCD monitor but not when I print it back to tape, still as HDV, and viewed back through the same LCD monitor. The version on Vimeo shows this and is no different from what I see on the clips before uploading them.

Thing is I know about de-interlacing and the BOTTOM CLIP above IS de-interlaced but still shows nasty blurring when viewed from the computer as the playback medium (and is clear in the Vimeo clip) which is never present when viewed from tape which suggests to me there 2 different issue here - the interlacing one AND something else I cannot fathom though Bryan suggestion about refresh rate is interesting. Though you may be right that despite de-interlacing it this still may be the root of the problem though I don't know what else I can do but de-interlace the footage!
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Old October 20th, 2009, 07:40 AM   #8
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OK. So you're viewing the clip on the same monitor but from two different sources. When you play back the interlaced footage from HDV tape there is no blurring but when playing back the same footage from computer there is. Do I have that right? If so the reason for the difference would appear to be that the device playing the HDV tape supports interlaced playback. Your computer does not. Thus computer playback will exhibit artifacts. Since I cannot see what those artifacts look like it's hard to know for certain if that is the root cause.

As to the artifacts visible in the first Vimeo clip, I am convinced that somewhere in the transcoding process, either at your end or Vimeo's, one of two things are happening. Either two interlaced fields are being mashed into one progressive frame (Vimeo is always progressive) or Vimeo is being fooled into another frame rate, like it's converting 25fps into 30fps. Without fields, that's hard to do cleanly.

I tend to believe that the first reason is more likely but there are numerous things that can go wrong in a conversion like this.
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Old October 20th, 2009, 11:46 AM   #9
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Thanks for the further advice Tripp and yes you are right about the difference between the 2 playback mediums and I agree that my HDV player (a very decent Sony player) must be able to read interlaced material.

As for the de-interlaced version it is tricky because without seeing what the clip should look like it is hard for others to see what I mean with respect to the blurring I'm concerned about. All I can say is if you watch the bike and motorbike pass they are quiet a bit more blurred than in the original - in fact all the movement is blurred slightly, even the swinging of the passers-by arms. Also look at the spokes on the car wheels - it is shot using a high shutter speed so these are really clear in the original too but very blurred on the de-interlaced version.
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Old October 21st, 2009, 12:00 AM   #10
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I think it might be frame blending that you are seeing, have you tried dropping a still of and see if that gives a clue, although that probably isn't possible.
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Old October 21st, 2009, 02:06 PM   #11
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Hi Bryan could you tell me what you mean by 'dropping a still of'? I should say that I used a motion compensated form of de-interlacing rather than frame blending though it might be that the de-interlacer has not done an especially good job on this specific footage and that is what is causing the problem.
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Old October 21st, 2009, 03:31 PM   #12
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Hi Geoffrey, I thought if you had made a video that had the jittery motion blur you could capture 1 frame and see if the problem was introduced by the editing software, If you look at a still from the original footage and then one from the jittery it might give a clue as to what is causing the problem, on my editing program it's called "Save as still image"
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Old December 11th, 2009, 06:15 AM   #13
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i dont get it (the motion blur) i DO see the post progressive interlaced thing (int), but the motion is clean on this Monitor, it is very CRISP albiet seperate (as opposed to motion) pictures at what seems to be a frame rate that is not fast enough for your shutter setting.
That is how they are doing the HD sporting events with fast movement, each seperate picture is shot at 1/250th - 1/2000th of a second, then played back at 60I which ends up being 30P on the average LCD screen, so you stop the "motion" , then play a few frames a sec. to see it.

well i didnt need to say that but, there is a balance between keeping the (expected) motion blur when the frame rate is so slow that your brain is still visualising a bunch of clean crisp pictures being rotoscoped. so SOME of the (lets call it) broken motion, is the high shutter. how else could you possibly shoot cars wizzing THROUGH your frame at some 25+MPH and not have motion blur.

of course you can't SEE what i see, because i can view YOUR progressive vimby flick on a CRT , which actually CAN change the picture fast, and a LCD that has a "faster" change rate for the light valves.

if your seeing motion blur and ghosting of the previous (well defined crisp image) then you probably dont have a "gaming" LCD monitor.
Standard LCD screens changed the picture at 25ms (if i remember right) and slower, then they came out with 15ms monitors, about then they changed the specs and LIED :-) they started "spec"ing the change rate of thier LCD valves from G-G or Grey to Grey, after that they made claim to 8ms LCD monitors , that STILL cant do 8ms full changes.
(ghosting of full on- full off images, in stark contrast)

so your LCD monitors processing, or LCD light valve changing rate is to slow, or your Set computer display rate doesnt match with your frame rate.

There is interlace that is obvious in the interlace one, the software did a proper job of slapping together the interlace, but your high shutter doesnt work with standard interlace to progressive changes, because you would have Normally had Motion blur THERE, and the blending of the feilds would have blended IN with the interlace feilds "blur" once made to progressive.

so back-up because i am not knocking anything, your picture looks Great, the technology for doing what you tried to do sucks :-) Lcds suck for frame rate, video frame rates are going backwards (lower), and interlace is being tossed.

check out your monitors specs for the LCD change rate, play it on a different monitor, or toss out the stupid LCD displays and go with a real CRT monitor that has some Colors, and frames :-) to late for that, digital is here , and vynl records are in museums.

if you went to film school and they told you a human percieves pictures changing at 18FPS as real motion, they lied :-) the human eye can percieve (about) 120fps motion before it blurs all up, movies and tv have been getting away with (less frames) tricking our eyes, by leaving in the motion blur, or even adding it Back in (see pixar 3D)

Last edited by Marty Welk; December 11th, 2009 at 01:17 PM.
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Old December 11th, 2009, 06:47 AM   #14
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Marty,

Thanks very much for your detailed answer which does make things much clearer. Yes I was trying to use a fast shutter to get that very crisp look but your explanation is certainly enlightening for a relative novice such as me and will inform my procedures from now on. The clip uploaded is by far the most problematic due to the rapid cross-screen movement, fast shutter etc.

The good news is that I bought an MXO2 Mini and used that instead of the Mac graphics card and the problem of the blurring (beyong what, as you say is the normal motion blur one would expect with this type of shot) is gone. It also deals with the interlaced footage brilliantly - no artifacts at all. My assumption is that the Mac graphics card just isn't good enough and perhaps that the Hz rating of the screen (60) as a result is wrong for the footage? When played through the MXO the screen defaults to correct rating - 50Hz. True, the refresh rate of the LCD screen I've got still isn't quite up to it but it now looks the same as when I play back the original tape. I also made a DVD and when played back on my DVD player it also looks smooth and fine.
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Old December 11th, 2009, 10:08 AM   #15
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Oh and btw Marty I still play vinyl!
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