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Old August 9th, 2003, 12:36 AM   #1
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Capture frame shifting artifact on PC screen

Hi everyone. I'm new here, but not new to DV. I've been shooting with GL1s since 2000, and two days ago finally brought home a brand spankin' new XL1S. Oh, the joy, the happiness! Unpacked it, assembled it, and headed out to shoot. Shot, went home, captured to the desktop. I noticed some picture artifact on capture. I would call them scan lines, except they are not black. What they are is a slight displacement of pixels to the left that run
in a line all the way across the frame. The artifact starts at the top, runs down to the bottom, goes away and then comes back again.

I played back the tape via the camera to three separate TV monitors and there is no picture artifact.

I shot a second tape, thinking it might simply be bad media, and the same thing occurred....artifact on capture and computer playback, no artifact on playback from the cam to the TV.

Played the tape through a gL1 to a TV monitor, no picture artifact.

Examined each frame on the timeline after import into Premiere, each frame is perfect, no misalignment, no pixel displacement.
By sheer dumb luck I managed to capture, then export, a misaligned frame during computer playback. The lower half of the frame is displaced to the right by at least an eighth of an inch. However, the corresponding frame on the timeline is perfect on visual inspection.

I exported the clip in question to tape, and there is no picture artifact when I playback the exported tape on a TV monitor.


I conclude that the problem is not the camera but the computer playback.


The problem is, I haven't seen this picture artifact before putting in the XL1S footage. I just upgraded my editor last month, to an XP OS, Asus MB with 2.8GHz Intel P4 Processor with an 800MHz FSB, 200 G AV HDD, 40 G archive HDD, 40G system HDD, Matrox RT100X capture card, Matrox Millennium Flex 3d Video card, Premiere 6.5, 512 DRR ram. It works as advertised; editing is a pleasure and a dream. I finished a piece on it using GL1 footage with no problems. I attached the XL1S to the computer and turned it on - no problem. Device control, no problem. Capture, no problem, except for the picture artifact.


Has anyone else had a similar experience? Any ideas?

TIA,
Barb
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Old August 11th, 2003, 03:42 AM   #2
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Does the system still capture OK from the GL1? Did you try to capture the XL1-S tape through the GL1?
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Old August 11th, 2003, 09:21 AM   #3
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Thank you so much for your reply. I have to decide within a day or two if the camera is defective or not and return it to the dealer, so I am feeling a little pressured right now. Your input was so welcome.

I did capture the same piece of tape with the GL1 and the picture artifact is definitely there. It's actually more pronounced with the XL1, but it is there in both capture on cpomputer playback.

Then I captured a different piece of tape that I knew to be perfect
with both cameras and there is no picture artifact with either camera on computer playback.

So,it appears that the tape shot with the XL1 has picture artifact
on computer playback no matter which capture device is used, whereas tape shot on another camera, edited and exported, does not have picture artifact when capyured with either camera.

Does anyone know if there is a name for this particular type
picture artifact?


TIA!!
Barbara
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Old August 11th, 2003, 02:06 PM   #4
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Can you post a screen shot?
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Old August 11th, 2003, 05:05 PM   #5
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<<<-- Originally posted by Dan Uneken : Can you post a screen shot? -->>>

www.adoptapundit.com/pics/misaligned.jpg


Here ya go. Thanks for the response!!

Barb
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Old August 12th, 2003, 01:21 AM   #6
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I would suggest to the "wrangler" to move this thread to the XL-1 watchdog forum, or instead, Barb, post it there as well. That forum is probably seen by many more techies.
I don't know how to call that displacement (there seem to be two: from the top, at the middle there is a displacement to the left and then the big one to the right). I would take back the camera, as you said it looks like you have eliminated other possibilities.
They should get that fixed for you real quick! All the best!
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Old August 12th, 2003, 03:38 AM   #7
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If you cannot see this problem on a TV it shouldn't be in the
actual recording.

Seeing that the posted pictures is NOT at the default DV resolution
I'm suspecting this is a capture from a playback window?

If you check it frame by frame there is no problem you say. This
points also in the direction of a playback problem instead of a
problem with your footage.

How did you precisely get that picture you put up?

If you capture and see these "artificats", you edit your footage,
put it back on tape and then play the tape back in the camera
to a TV, do you see the artifacts?
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Old August 12th, 2003, 04:40 AM   #8
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It could be dirty heads, problem heads or a firmware glitch. If cleaning the heads didn't work, and only one brand/type of tape was used, I would just return the cam.
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Old August 12th, 2003, 07:00 AM   #9
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While the cause of the anomaly could be either the camera or PC, I agree with Frank. It is some kind of error induced by the electronics. Possibly the cameras drop out compensator, or similar in the video card in the PC. I would try as many tapes as possible from the GL1 in the PC. If you can duplicate the results it's not the XL1. It doesn't mean the XL1 is defective, just the two pieces of equipment will not work together in their present state of adjustment.
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Old August 12th, 2003, 10:11 PM   #10
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Thank you for the input, guys. Much appreciated.

When we updated this system to the new Matrox RTX and the new processor, we wondered if the Matrox Millennium 3D Flex card would be enough to handle the load. It works fine with the GLs. So, we are wondering about the video card.

What is drop out compensation in the camera?


Do you think it might be some kind of mismarch between the progressive scan of the computer and the increased number of horizontal lines that the XL1 delivers in interlaced form? I tried deinterlacing some tape, with no real difference. I notice in the settings viewer that all the options are set to lower field first except the test avi, where no field preference is specified ( it says no fields)

Do you think it might be a mismatch in the capture setting in Premiere ( currently set to capture via Matrox DV 1394 input?)

If this is some kind of electronic anomaly, how would I go about reconciling the two pieces of equipment?
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Old August 12th, 2003, 10:16 PM   #11
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Quote:
Seeing that the posted pictures is NOT at the default DV resolution I'm suspecting this is a capture from a playback window?
Yes, it is. I captured it by sheer dumb luck from the monitor wondow as it played back from the timeline. Stopped the playback at a time I knew I was seeing artifact, exported the frame and there it was. Sheer luck.

Quote:
If you check it frame by frame there is no problem you say. This points also in the direction of a playback problem instead of a problem with your footage.
Right, and I agree.

Quote:
How did you precisely get that picture you put up?
See above.

Quote:
If you capture and see these "artificats", you edit your footage, put it back on tape and then play the tape back in the camera to a TV, do you see the artifacts?
No, I don't see them on a tv at all. Did this with two separate tapes I shot with the XL,, actually. Put them each on a time line, examnned them frame by frame, saw no problem anywere with any still, exported the timeline to tape, and watched on tv - no problem. Also no problem palying it on a tv the first time. Problem only show up in computer playback.

Video card, maybe???
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Old August 12th, 2003, 10:54 PM   #12
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<<<-- Originally posted by Dan Uneken : I would suggest to the "wrangler" to move this thread to the XL-1 watchdog forum, or instead, Barb, post it there as well. That forum is probably seen by many more techies.
I don't know how to call that displacement (there seem to be two: from the top, at the middle there is a displacement to the left and then the big one to the right). I would take back the camera, as you said it looks like you have eliminated other possibilities.
They should get that fixed for you real quick! All the best! -->>>



How do I move it? EEK!

Hehehe,
Barb
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Old August 12th, 2003, 11:17 PM   #13
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Barb, unfortunately only a forum's Wrangler can move a thread to a different forum once it has been posted. Fortunately the DVi Community has vigilant Wranglers.

Since you have already established that the problem is with the PC and not the camera (same issue present when capturing from GL1), this post is in the right place.
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Old August 13th, 2003, 01:06 AM   #14
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TV's are very forgiving of low quality or marginal quality video signals. The fact that you do not see the anomaly on a TV, even from 2 different cameras, doesn't mean a great deal.

Video devices that accept video for input, live NLE, DVE, and duplicating equipment are much less forgiving than monitors.

The anomaly could have several causes, the tape was defective in manufacture, the camera that recorded the image is slightly out of adjustment, or the video card is slightly out of adjustment. It could even be a combination of all three.

How do I determine the cause? Well, yo may not be able to, but here are some things to try. Use another tape and see if you can duplicate the error. Use another camera and see if you can duplicate the error. Try capturing the tape to another NLE, same brand, different brand, really doesn't matter.

If another tape shows the error, it is probably not a defective tape problem. If only the tapes recorded with the XL1 show the error, it could be the camera. If tapes recorded with another camera also show the error, it probably is the video card. If the error only occurs with one camera and video card, then a slight mismatch might be occurring.. Both pieces of equipment might need adjustment.

A video signal standard is like a yard stick. The specifications for DV are not an absolute. If they were, it would almost be impossible to interchange tapes from one VCR to another. However, the camera can be adjusted to one end of the yard stick and the video card to the other end. When the camera plays back a tape that needs error correction (possibly a dropout) the camera uses error correction to try to correct the problem. The video card reacts to the correction in the wrong way and a visible error occurs on playback through the card. If several cameras and several tapes can cause the problem, then the error probably lies in the video card.
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Old August 13th, 2003, 08:02 AM   #15
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Jeff,
I've done several of the tests you have sugested and the results point to the pc, not the camera. Tapes shot earlier with the GL1q work fin on the system. tapes shot with the XL1 have the artifact. If I capture the tape shot with the XL1 using the GL1, the artifact is there. If I use the XL1 to capture tape shot with the GL1 or exported to tape after edit via the GL1, the artifact is not there. It has to do with the tape shot by the XL1 and my PC.

I suspect it may be the video card as
the one I am using is not supported for the rest of my newly upgraded system The vid card that is in now worked well with the input from the GL1s and the problem started showing up only with the XL1. I guess there is something in the output of the XL1 that is out of adjustment, as you say, with the vid card.



How do you adjust the camera or the video card?

Is there a procedure somehere I coud read?


TIA
Barb
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