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Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


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Old July 3rd, 2004, 03:45 AM   #1
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Motion Artifacts

When I shoot in frame mode or at 1/30 shutter speed, while panning slow to moderately, and playback or shoot in camera mode to a TV (I've tried several), my GL2 is producing motion artifacts (although the frames do not have artifacts when paused in VCR mode). However, when I put this onto my computer via firewire, there are no motion artifacts.
And when I put my 60i footage onto a computer, it does the exact same motion artifacts that my TV was doing to frame movie mode. Whereas when I play this 60i footage on a TV, it comes out perfect, not motion artifacts.
Even when I take 60i footage and convert it to 30p in Vegas 5, and export it back onto my camcorder, I still have the same problem when I hook my GL2 up to my TV and play it back! Although not as badly as frame mode.

Here's a link to a picture that looks pretty much exactly how frame mode shows up on my TV while panning:

http://www.geocities.com/ianmhong/GL2.html

Please help!!
Is this normal or not?
Has anyone else experienced this?
I know I've posted a very similar thread, but I hope the picture and additional information will help to answer my questions.

Thank you,
Ian Hong
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Old July 3rd, 2004, 04:30 AM   #2
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There's nothing abnormal here at all - when you show frame mode material on a tv, you'll get a slight jerkiness which is supposed to look like film (!) but it will show fine on a computer monitor.
Whereas normal mode (interlaced) shown on a computer will show up the interlacing combing effects. It's all in the way that the two different systems display video.

Robin.
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Old July 3rd, 2004, 07:39 AM   #3
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Output to DVD

If you take that frame mode footage and output to a DVD via Adobe Encore (for an example), will it still have that jerkiness to the footage, or does the transcoding process of dvd creation minimize it?
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Old July 3rd, 2004, 07:46 AM   #4
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Although Robin is basically correct he is not talking about your
problems. If your footage looks like the footage you linked to
on your **TV** you have some serious problems.

I'm almost certain you have done some sort of field reversal
to get this effect. Most probably this happened while shooting
in interlaced, not frame. Are you 1000% certain you shot the
footage in frame mode?

Please give us the full laydown on how you captured the footage
and HOW EXACTLY you displayed it on your TV. Camera out,
DVD out etc. Also tell us what you exactly did to the footage and
which software you used to do all of this with.
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Old July 3rd, 2004, 11:42 AM   #5
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Okay.

The picture I displayed on the internet is 60i footage, on my computer, while editing in Vegas 5. But I noticed that this footage looked exactly like the footage when I pan in frame mode and hook my GL2 up to a TV. So I'm displaying it only because it looks exactly like frame mode when I connect my GL2 to a TV. I have hooked my GL2 up to several TVs via s-video and A/V. Without recording, in camera mode, while panning, and in frame mode or 1/30 shutter speed, it does almost exactly as in the photo. Then when I also record this, and playback, it also shows up as in the photo, when played back on any TV via s-video or A/V, although when I pause the video, the picture looks perfect.

When I capture the frame video onto a computer, the images look and play perfect! No artifacts! I have Vegas 5, but no CD or DVD burner yet! So I'm not sure how the frame mode images would look if I burned to a CD or DVD and played them on a TV. But if I render the phootage as field order: none (progressive), deinterlace method: Blend fields, and video format: NTSC DV. And print it to a tape in my GL2 with no added effects at all...bingo, the artifacts are back.

I'm probably about a 1,000,000% certain it was in frame mode. :)

So I decided to try deinterlacing 60i footage since my frame footage wasn't working properly and I need progressive video. I did it in Vegas 5, using no effects, only changing the properties and rendering it as field order: none (progressive), deinterlace method: Blend fields, and video format: NTSC DV. I rendered it and then printed it to a tape in my GL2, since this is the only way I can watch it on a TV since I don't have a burner! I hooked up my GL2 with the new footage to a TV, and, sure enough, there was the same motion artifacts again as in the photo. Although it wasn't quite as bad as frame mode, I think this is because there tends to be more bluring of the image when Vegas deinterlaces than frame mode.

I have a short film I'm starting to shoot in ten days! I know it was stupid of me to wait until now, but I've been so bogged down with other aspects of the film.

I'll be forever grateful to anyone who can help me!

-Ian Hong
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Old July 3rd, 2004, 12:55 PM   #6
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That still shot sure looks interlaced to me, Ian.

Ian, are you new to the GL2? What exposure mode are you using?
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Old July 3rd, 2004, 01:31 PM   #7
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I got my GL2 about 7 months ago. I'd say I'm proficient in every aspect the manual covers.
By exposure mode you mean whether it is in Auto, Tv, Av, Manual, Sand&Snow, or Spotlight, right?
I've tried it in manual and auto exposure in frame mode, and it produces the artifacts as said.
And when in manual exposure, I slow the shutter speed to 1/30 in normal movie mode, it still shows the artifacts.

My GL2's microphone was hit by somebody's head a few months ago, but the microphone still works perfectly, and all the footage I have from before the accident has the same motion artifacts, could it possibly be from this?
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Old July 3rd, 2004, 04:09 PM   #8
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Robin is right. The "mouse teeth" you "see" is because frame mode or 1/30. both are displayed (on a non progressive displays) as interlaced field sequences with the specific property that the field's content refreshing happens only every two fields (against every field in 60i !). The eye "sees" this non continous field refreshing as "mouse teeth" or "double images" when there is a certain amount of horizontal motion. This is even more visible on horizontal (frame mode) text scrolling. When seen after recording as a freeze frame there will be no problems because the discontinuity isn't there: you get the two fields continiously repeated. If you deinterlace 60i footage using blending the problem will be reduced because the lines are summed up, and so do the "mouse teeth"
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Old July 3rd, 2004, 05:31 PM   #9
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I don't know what else to say. I have not seen this on my XL1S.
Yes, I've seen stuttering etc. due to low shutter speeds and/or
frame mode. But nothing that looks like interlacing (unless it was
shot in interlaced and I watched in on my computer.)
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Old July 4th, 2004, 03:44 AM   #10
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The artifact is best seen on a standard interlaced scan TV (no rescaling, frame rate doubling...) with frame mode pictures preferably with higher shutterspeed settings in order to reduce motion blurr which smooths the visibility of this artifact. Many TV's screens don't have optimal interlace (partial line pairing) which again makes this artifact less visible.
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Old July 4th, 2004, 05:30 AM   #11
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I have a standard interlacing TV but it isn't showing this. I am in
PAL land, however. Did you test this on multiple TV's? Sounds like
you did.
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Old July 4th, 2004, 10:39 AM   #12
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Rob, are you viewing at a distance where you see line structures and interline flicker (line twitter) on vertical transients? Do you see the normal motion judder which comes with frame mode displaying on a standard TV? Try to follow the judder parts in the picture and you should "see" the mouse teeth. This judder perception is one of the reasons why frame mode displaying is not like real film projection. Film flashes full pics (not interlaced field sequences) all the time... so there is only a clean judder.
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Old July 4th, 2004, 11:51 AM   #13
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I've tried it on 4 different sets. I have a 50'' Panasonic CinemaVision HDTV, and I've tried it on two other smaller bubble-type sets, and the same thing still happens, although, it's not as apparent because of the smaller size, it's not even visible on a 20'' TV I tried

Well, this morning I took my 60i footage which was looking perfect on my television, and changed it to 30p, and burned it to a VideoCD in Vegas as an mpeg file. I popped it in my DVD player, and the mouse teeth are still there.

Rob, I tried rendering my 60i footage to 24p in Vegas, and I didn't see any mouse teeth, so maybe this is why you're not seeing it? Although there was a lot of blurring in the 24p conversion.
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Old July 5th, 2004, 03:51 AM   #14
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Well the only thing I can say is that I am shooting in frame mode
and displaying on a not too good TV. What I find weird is the
following:

1) if you shoot in frame mode then there is no time difference between the frame, so there are no "teeth"

2) if this would be a problem you would not be able to watch a lot of commercial DVD's out there since they are encoded progressively as well

So in my conclusion either something else is very wrong or it
does not happen in PAL 25 fps land.

Andre: I do not see any of those things. I occasionally see some
stutter over the whole frame when it moves due to the nature
of progressive and shutter speeds. Perhaps I need to look closer.
I will check some footage this week from both SVCD / DVD and
DV directly.
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Old July 5th, 2004, 05:17 AM   #15
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Rob, moviemakers have "rules" as you certainly know which advise against too fast motion. But even when the problem shows up this doesn't mean that one "would not be able to watch". There are more artifacts in interlace TV which are tolerated. And indeed there is no time difference between two fields in a frame, but the last field of a framemode frame (in interlaced TV) and the first field of the next frame contain motion...
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