Image Pulses 2X sec XH A1? at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old December 15th, 2006, 06:36 PM   #1
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Image Pulses 2X sec XH A1?

I just shot some nature scenes of a brook with rocks, moss and water. I captured the footage (inches) direct from the camera shot at 1080i HD. I put the clips in the time line and saved the project. Still as HD. Then used iDVD to burn a DVD. I thought though I may be wrong that it was encoded or down rezed to the DVD. Only a couple of the scenes exhibited this 2x per second pulsing. Almost like frames going by. The whole image doesnt disappear it just pulses like someone turning volume up and down twice a second. Not all the way down...and not all the way up. Again this only occcurs in a couple of scenes. nothing changed. ??? Any ideas? Frame rate?
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Old December 15th, 2006, 07:02 PM   #2
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I had a similiar issue yesterday after encoding to DVD. I will try an look into the matter further.
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Old December 15th, 2006, 07:06 PM   #3
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I am only guessing here but two things spring to mind.

If there is high contrast textural detail plus large scale movement in the image, the DVD software, may be, in combination with the original footage itself, finding an excessive data rate and then may be playing an averaging game and softening the footage in alternating GOP segments.

If the pulsing effect you describe is not a brightness and contrast variation but a resolution (softness or pixellation) variation, then this may be what is going on.

My personal preference would be in this sequence of priorties,.

Try a two-pass coding option if this is permitted by your software,

de-interlacing the HD footage before export to DVD if this is an option, which might reduce the data load,

rescaling to SD and exporting to SD, then making your DVD from that file

or using third party software options which have been said on other threads at this site to yield better results. (VirtualDub and Tsunami?? are two such mentioned).

Please do not pay to much heed to my comments but wait for someone else to come along, otherwise you may kick your toe blindly on the same kerbstones as I do.
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Old December 15th, 2006, 07:12 PM   #4
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Holly I am embarrased to say but I just used my ImovieHD program on my Mac because it has 8 gigs of ram and is dual core 2.5 so it is faster than my PC which is only a 1.8 Centrino Vaio. That has Vegas 7. Again all i did was save the project no transitions or effects just video and audio. It was captured to the MAC in HD it was saved. I created the DVD in IDVD. It was about a 20gig project 14 minutes. Just a test. Played the DVD in my DVD player on a 26 inch Sony HD Bravia. Just noticed that only a few scenes were doing that "pulsing" thing. Hope it is something I did not the XH A1. The other shots looked fantastic. I don't knowif they would show as mov file online. Have not gotten that far yet.
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Old December 15th, 2006, 07:19 PM   #5
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Thanks to both of you...

The scenes that are doing this pulsing thing do have cascading rythmic white water whatever you want to call it in the shot. I will try taking a couple of the same clips that I did on the Mac and see if I get the same thing on the Vegas. I captured some of the same footage off the camera there as well. Maybe iDVD just can't handle or isn't designed to handle the data load efficiently. I sure would not know that's for sure!
Thanks Loooking for more suggestions if anyone has any.
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Old December 15th, 2006, 07:49 PM   #6
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That was quick.

Waterfalls. Beautiful shots.

The limitation as I understand things is not the softwares or hardwares so much as the mpeg2 codec itself which sets rules as to how much data can be passed. Obviously some softwares and hardwares will implement these rules better than others but if that multipass option is available, then using it may help.

If you shot a 1/100th sec or faster shutter on the falls, the very way I would want to see them, there definitely will be a high data load.

My personal preference in that instance would be to import the troublesome clips into an effects software, use a frame blending function to soften the image movements as if there was motion blur there, then render out the clips and re-import those.

I have done someting similar in Premiere 6 in SD for gain noise reduction which I have for want of better definition called layer stacking.

I do not use the master video track at all, but create up to five video tracks on the timeline. I place an identical clip on each track, but each clip is one frame furthur along the timline and the transparency of each is set at the percentage divisor of the number of tracks I have used.

Example five tracks, transparency 20%. There is no logic in the way I chose to do this, only blind experimentation. There is a video "echo" effect on movement which has the effectof softening moving textures.

You take a resolution hit in rendering out of Premiere 6. Premiere Pro2 or Vegas may perform better nowadays.

The simulating motion picture clarity resource article posted here at dvinfo which uses a method of interpreting footage into separate upper and lower fields, then laying each over the other, seems to be a de-interlacing function which simulates motion blur.

Once rendered, these clips might also come within the limits permitted by the mpeg2 codec.

Pity about the loss of clarity in the falling water though. It also challenges film imaging like the spokes of wagon wheels because altough the human eye cannot see it, there are sometimes repetitive patterns and standing waves to be seen in motion images of falling water.

EDIT:

Something else I just forgot and now remembers is the "cadence" effect of 24P or 25P being translated from NTSC interlaced footage and vice versa, - all those pulldown rules we in PAL country don't have to concern ourselves about as much. This may be one of the toebreaking kerbs I cautioned about when following any advice I offer.
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Old December 15th, 2006, 08:05 PM   #7
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It's mostly the surrounding dark areas that you can see this pulsing. Again it's a very steady and regular "image pulse" (Idon't know what else to call it)about 2 times per second, almost as if you are watching an overlay of a frame by frame. It is noticable in the dark shadows and blacks.
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Old December 16th, 2006, 10:59 AM   #8
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HX A1 "Image Pulses"

I checked both clips.
They both were "pulsing".
Both the PC with Vegas 7 and the same Clip I captured to the Mac are doing this.
Oddly non of the other clips shot at the same time exhibit this 2x per second flicker.
It looks as if you are running the DVD in slow motion. Although it is not. There is a color shift in the shadows with each "pulse". I don't think it could be seen on a computer LCD but if anyone thinks it would help I can try to upload 65MB file or so to this forum. Any help or ideas would be very much appreciated.
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Old December 16th, 2006, 11:04 AM   #9
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You didn't happen to be shooting in an auto mode with auto shutter on, did you?
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Old December 16th, 2006, 11:07 AM   #10
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Completely Manual I think. I was trying out a preset #9 that comes with the camera. I believe the shutter was at 100 or 120th sec. Stab,AF,AGC,AWB was off.
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Old December 16th, 2006, 11:12 AM   #11
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The fast shutter speed could have something to do with it.
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Old December 16th, 2006, 11:31 AM   #12
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How? Could you explain in lay terms?
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Old December 16th, 2006, 11:33 AM   #13
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Burdened by the data load in passing the detail of the falling water, the mpeg2 codec seems like it may be completely ignoring the dark area for the full group of pictures which I think is once every half-second and redoing the entire frame. If this area is constantly dark there should be no problem.

If there is a dynamic lighting of this dark area through reflections off the water or moving shadows from leafy canopy of trees, then changes to the image, because they are very subtle, might only be getting reproduced at each keyframe

If you increase the brightness on your display, can you see large pixellations within this dark area?

Before trying more to fix this, it might be worthwhile viewing your camera footage direct from camera in a high resolution monitor with the brightness turned up to see if there are large pixellations in the camera footage in those dark areas.

My personal preference might now be to reduce the detail in the falling water by blending the frames or applying the motion clarity recipe published here at dvinfo, also increasing contrast or deepening the dark area where the pulsing occurs to bury it in black. I might be inclined to bury the dark area in black with higher contrast first before trying other things.

If you are not already using Cineform's Aspect HD and using the Cineform "lossless codec" for editing, it might be worthwhile downloading and installing the latest trial version, recapturing the troublesome clips with standalone Aspect HD and select de-interlace in preferences (findable in a little box on the lower left of the Aspect HD's own interface) to see if this helps with the problem.

It seems to do quite well with an aggressively moving subject like a zoomed close-in pan follow of a low flying aircfaft with the ground and shrubs in the background moving throug the frame very fast.
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Old December 16th, 2006, 11:44 AM   #14
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I also should mention that I just went back since the A1 was still on the first tape it came with, that the Versions I shot in SD and made a DVD with don't exhibit this pulsing thing.
Also and here it goes...I switched tapes to JVC ProHD tape from the tape Canon includes with the camera. I know I have read the long Black Line Tape thread. I intend to use one type of tape. But would it have made any difference swithin fro the Canon tape to JVC after just one play. I did FF and Rev the tape on the camera a few times before I read about that not being a good idea. Record tape once play tape once will be my future motto.

Is there a place to buy Canon tapes in bulk likr the one that came with the camera XH A1 that is?
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Old December 16th, 2006, 12:02 PM   #15
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I don't think the tape is the problem. If there was pixellation from dropouts on the tape the image would be more mutilated with maybe even a half-second dead spot.

I was trying to get another edit in on the post above before it timed out but I lost.

It still seems to me to be a mpeg2 compression thing.

If the contrast adjustment does not work, another option might be to bring up the brightness to burn out the water slightly and reduce contrast so that the dark area becomes brighter and maybe any fluctuation on the brightness or hue becomes less evident.

If there is no defect apparent in the camerafootage on a hi definition monitor, the only last desperate measure I can think of would be to add video noise as an effect then render to see if the added detail in the dark areas forces the DVD process to sample the dark area more often than the half-second intervals.

You might lose some resolution in the waterfall.

This is all a high science outside of my expertise so do not treat my comments too seriously.
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