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Sony HVR-Z1 / HDR-FX1
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Old December 24th, 2005, 07:36 PM   #1
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Flickering images at slow motion

I am starting to get upset. Everytime i make a slow motion from HDV 50i to 50% speed, some parts of image start to flicker.
Does anyone notice this?

Here is an extreme example of the problem. Sometimes you dont see the issue. Sometimes footage becames unusable.
How can we fix this? Why is it produced?

www.neotokio.org/flicker.mov

thanks!
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Old December 24th, 2005, 08:06 PM   #2
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I see the flicker. What shutter speed did you use? What software did you use to slow the footage down?
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Old December 24th, 2005, 10:38 PM   #3
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I haven't downloaded your clip to view yet...

What are you using to edit; Mac or PC?

As Boyd mentioned, shutter speed is important, as well as whether you changed frame rate.

If you rendered out to say a 24p final from 25p or 50i that had not been slowed, then you could end up either exceeding the boundaries of your computers processing power, or the capabilities of your software to drop frames (changing frame rate) while actually making them during the slowmotion process as well as de-interlacing!! Thats' a lot to ask of any software or system...

See if you can slow your clips first... using something uncompressed: like Cineform CFHD AVI on PC or LumiereHD on Mac, before rendering to your final format.

Without much extra info from your end, it makes knowing what the cause and solution could be kinda difficult.
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Old December 24th, 2005, 10:53 PM   #4
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I haven't downloaded your clip to view yet...

What are you using to edit; Mac or PC?

As Boyd mentioned, shutter speed is important, as well as whether you changed frame rate.

If you rendered out to say a 24p final from 30p or 60i that had not been slowed, then you could end up either exceeding the boundaries of your computers processing power, or the capabilities of your software to drop frames (changing frame rate) while actually making them during the slowmotion process as well as de-interlacing!! Thats' a lot to ask of any software or system...

See if you can slow your clips first... using something uncompressed: like Cineform CFHD AVI on PC or LumiereHD on Mac, before rendering to your final format.

Without much extra info from your end, it makes knowing what the cause and solution could be.

Either way: I was just mucking around doing a slow-mo experiment on some FX-1e PAL 50i stuff I shot of buzzing insects and flutterbys. The extremely short HD 1920x1080 25p clip I've linked below is 3X longer than it's original length, and as far as I can tell it seems pretty smooth in the motion and lack of artifacting around the bug as it lifts off. This ain't no artistic test... just an experiment in using the CTRL key in Vegas when time stretching a clip on the timeline.

If you can't view the clip using OS supplied media player software, download VLC - free for Mac/PC, or Media Player Classic for PC - also free!!

http://www.pnc.com.au/~scris/hd_images/

Hope that link works... just save the "Bug slow-mo test 1.mpg" to view it I guess!!
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Old December 24th, 2005, 11:10 PM   #5
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There's times I love technology, and times I wish it to Hell!!

I noticed how slowish the transfer was on the mpeg when I was uploading it, so I stopped it... quit the ftp transfer and rebooted just to re-intialize all connections.

Deleted the chunks from the previous transfer, and started transferring again... much faster as expected. What I didn't expect was the file size mis-match when it completed!! The clip ends prematurely because it's missing about 4-5meg!!

You just gotta love the digital age... If snail mail arrived with chunks missing we'd be pretty upset!! With digital; we're not even aware of missing bits unless you check and re-check stuff you've taken for granted as working.

Oh well... re-uploading
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Old December 25th, 2005, 12:29 AM   #6
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Well... It'd be nice to be able to up my server allocation with my ISP. Until the day that happens, the attenuated clip that's linked to is just gonna have to do. I refuse to convert to some WMV9 of crummy bit-rate, or down-rez to 720 or any other degraded in some form version of the original.
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Old December 25th, 2005, 06:49 AM   #7
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The shutter speed is 1/100.
Remember this is recorded at 50i because i am in a PAL country.

Slow motion has been done in Vegas, setting speed at 50% so from each HDV field you get a full rame. At SD resolution i get very decent images.
However some parts of the image sometimes flicker, speacilly with some colors. Skin tones suffer the most. Si i guess it has something to do with color compression.

This is an example of medium flicker. Look at the right part of the girls´face and her shoulder. there is flickering there and it is not a problem of QUicktime sorenson compresion.

http://www.neotokio.org/ellas.mov
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Old December 25th, 2005, 08:28 AM   #8
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Quote:
Originally Posted by Miguel Lopez
The shutter speed is 1/100.
Remember this is recorded at 50i because i am in a PAL country.

Slow motion has been done in Vegas, setting speed at 50% so from each HDV field you get a full rame. At SD resolution i get very decent images.
However some parts of the image sometimes flicker, speacilly with some colors. Skin tones suffer the most. Si i guess it has something to do with color compression.

This is an example of medium flicker. Look at the right part of the girls´face and her shoulder. there is flickering there and it is not a problem of QUicktime sorenson compresion.

http://www.neotokio.org/ellas.mov
Did you use an envelope in Vegas to do the slow-mo? Or did you CTRL-drag the edge of your clip to double the clip time on the timeline?

Did you render as 25p progressive or retain 50i interlaced frame rate? If you went progressive, what de-interlace setting did you select?

If you stayed interlaced, are you certain that the QT player preferences for de-interlace modes is set?

Try writing the exact same Vegas project to a progressive HD 1440x1080, 1.3333 Pixel Aspect Ratio MPEG2 just to see whether it produces the same effect.

1/100 would not be my choice for shutter speed for slow-mo, but whether it would cause the effect you are seeing... I don't know.
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Old December 25th, 2005, 09:39 AM   #9
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Quote:
Originally Posted by Steve Crisdale
1/100 would not be my choice for shutter speed for slow-mo, but whether it would cause the effect you are seeing... I don't know.
I agree. You might try the same thing again while shooting at 1/50 sec shutter speed and see if that helps.
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Old December 25th, 2005, 09:40 AM   #10
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Quick reply:
I use 1/100 because it is the way to go as a film camera would do.
The flicker is not a couse of artificial light. both clips have sun light.

The slow motion is done by setting the playback rate at 0,5. It is the same as if i would apply a velocity envelope and set it to 50%.

Then i render a 25p video. It doesnt matter wather it is full res, wmv, avi, mpeg, the same issue appears always even in the preview window.

There is no need to apply any deinterlace method. Vegas does the interpolation from each field atomatically.

I´ve done this with footage from DVX100e, xl1, pd150, betacam and DVcam and never had any problems.
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Old December 25th, 2005, 12:54 PM   #11
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Making slow motions from a shutter speed of 1/50 doesnt look right to me. It gives the same movement as video at 1/25, which i hate.
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