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Old October 4th, 2008, 01:33 PM   #1
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Pixelation from high motion

I've just returned from shooting a commercial using a hd200e and am overall very happy with the images.

However, one scene involved shooting a group of galloping horses from the back of my vehicle. The footage in this particular scene is dreadful. It's pixelated and looks like it was shot with a good mobile phone.

I've never shot any fast moving objects with this camera before so cannot speak from experience but have I just uncovered one of the limitations of HDV or this camera?

The scene was shot using 50p.

Any ideas?

note: I should add that the grey streaks you can see are rain. It was pissing down and wind speed was about 50kph. The vehicle was travelling at about 50kph.
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Pixelation from high motion-horse-roto-1-020.jpg  

Last edited by Stuart Campbell; October 4th, 2008 at 01:37 PM. Reason: further info
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Old October 4th, 2008, 02:07 PM   #2
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Thats just HDV compression for you. It cant handle lots of motion in the frame, especially at the 50/60p rate.
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Old October 4th, 2008, 02:13 PM   #3
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Thanks Drew,

I imagined there'd be some but it's much much worse than I originally expected

Bugger!
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Old October 4th, 2008, 04:04 PM   #4
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Stuart: I noticed the image is named Roto something or other. This leads me to believe you were looking to rotoscope out a horse or something. How does the footage hold up in motion? My still frames of faster motion stuff look rough but the images look quite reasonable in motion.

PS. I shoot in 720P60 exclusively.
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Old October 4th, 2008, 09:33 PM   #5
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The GOP is twice as long in 50P or 60P mode so there is more chance of this type of blocking happening during fast motion. The idea with Mpeg2 is that it is efficient for encoding, storing, and playing back motion images but it not ideal for frame grabs of motion.
Your example is about as bad as it gets for HDV1.
JVC uses 6 frame GOP for 24P, 25P and 30P and 12 frame GOP for 50P & 60P. The data rate is always 19.2Mbps regardless of frame rate (HDV1).
If it is any consolation HDV2 (1080i) breaks up even worse when encoding fast motion, even though it uses a higher bitrate (25Mbps.)
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Old October 6th, 2008, 12:58 AM   #6
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Cheers Guys,

Roto refers to the sequence as a whole. This is a cutaway from a locked off shot where we roto 6 horses charging toward camera and duplicate them into about 60 or so. So, as these moving shots are only to be used as very fast cutaways I think I'll get away with it. (just)

However, anyone know of a way of smoothing this footage effectively? It really is bad.

I'd originally intended to shoot 25p. But I wanted to slo mo some of the side on cutaways. Maybe wish I had done now and avoided the slo mo.

Tim that's interesting about 1080i. I'd have thought it would be better!

I must say I'm really quite shocked at how bad motion can be under this compression. It's a bit of an eye opener!!!
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Old October 6th, 2008, 04:22 AM   #7
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I've been back through all rushes with ANY sort of movement in and carefully analysed each shot for these such issues. I'm totally horrified. ANY movement in the camera or background gives a blurring or pixelation that is quite uncomfortable on the eye.

It's so bad it's almost unusable especially when the camera moves from a still shot. For example, I've got a couple of crane moves from a still position and bloody hell do you notice it as soon as the camera moves.

Horrible!!

Lesson learned.
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Old October 6th, 2008, 02:20 PM   #8
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The only way to cover that up is to emulate some sort of vintage super 8 in post. Obviously not possible in the context of a crane shot!

I feel for you man!
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Old December 15th, 2008, 02:06 PM   #9
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Stuart, that's a very important lesson you've been subjected to - Thank you very much for passing it on to us, I'll be carefully checking that one out before I shoot at 50 or 60. I'm really sorry as well as grateful, it's hellish coming in with poor rushes, obviously to be avoided at all costs.
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