Way OT: Lines or pixels moving through video image

Posted by Tim Stansbury 
Way OT: Lines or pixels moving through video image
July 12, 2009 12:01PM
This is way off topic as it not a problem created by FCP. More of a camera engineer question. I have a JVC GY DV5000 that I recently used for a video shoot. The video images often have moving lines somewhere within the shot, or in some cases lots of moving dots. Seems to be in darker areas of the picture. Has anyone seen this before or know what it is caused by? It's an old camera that I will probably retire rather than take in for repair but I'm still curious as I've never seen anything like this. Thanks. Still frame samples are at [s302.photobucket.com]
Re: Way OT: Lines or pixels moving through video image
July 12, 2009 12:12PM
I had something Similar from a music video shoot with the EX1 but we never got to the bottom of it.

What are your settings for the footage and for the sequence in FCP?

I've not seen this in DV before.


Does it resemble this?

[www.loudandfast.co.uk]



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Re: Way OT: Lines or pixels moving through video image
July 12, 2009 12:25PM
Yes, looks just like that! It's in the raw footage so has nothing to do with FCP settings. I don't remember anything unusual about the cameras settings - other than I was in auto preset white balance. FCP settings match what I was shooting, NTSC 29.97 standard DV.
Re: Way OT: Lines or pixels moving through video image
July 12, 2009 12:46PM
Yeah it was on our raw footage as well. I asked because in case it was something you noticed after digitising/transfer/transcoding.

I'm as stumped as you as to the cause as we were never able to repeat it even on the same shoot with the same camera.

I wouldn't even like to guess now as I thought it may be a weird MPEG compression error or an issue with the CMOS sensor in the EX1 but the DV5000 is DV and uses CCDs!

Hopefully someone will know - but I think for the footage you shot you will have to do a bit of a repair job as we did. luckily for us the issue was on out of focus backgrounds - yours might be a bit more tricky to fix. Try selecting the colour and isolating it with the 3 way colour corrector and taking the value down so it matches the surrounding areas.



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Re: Way OT: Lines or pixels moving through video image
July 14, 2009 01:44PM
The wavy line behind the singer? Could it be a banding issue? Like bit depth wasn't enough for all the color changes? What happens if some kind of dither is applied? (And where would that be?)

Just notions...

- Loren
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Re: Way OT: Lines or pixels moving through video image
July 14, 2009 01:52PM
It only appeared on some clips and wasn't on the viewing monitor but was on the source EX footage and the ProRes converts.

I simply matted it out with a travelling matte and blur. So it wasn't a big deal. I would like to know what it was though for future reference. Especially if there is a way to avoid it.



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