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Old December 21st, 2007, 10:57 AM   #16
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I'm just curious if you see as much of the "artifacting" at a slower shutter speed. HDV does work on a GOP principle, where processor attempt to modify only changing information in each succeeding frame in the group of pictures. It would seem that motion blur at slower shutter speeds would be less stressful in the process.... Any wizards out there got a thought...

The other thing that could be at issue, is what you are viewing it on. I have a cheapy HD TV. On some big time broadcasts I receive over the air, like football games, I will notice some blocking in fast pans. Is it the what's going on in the camera, or is it at the truck at the football stadium, the uplink to sattelite, downlink to the local affiliate, or in how my TV process the signal.... Don't really know, but I know that most of the time, the pictue is spetacular.
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Old December 21st, 2007, 11:30 AM   #17
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The other thing that could be at issue, is what you are viewing it on. I have a cheapy HD TV. On some big time broadcasts I receive over the air, like football games, I will notice some blocking in fast pans. Is it the what's going on in the camera, or is it at the truck at the football stadium, the uplink to sattelite, downlink to the local affiliate, or in how my TV process the signal.... Don't really know, but I know that most of the time, the pictue is spetacular.
Ah, you've hit upon something there.
It's definitely NOT the cameras. These guys use top of the line cameras and are usually spitting a straight uncompressed signal to the truck. Where the blocking/artifacting is introduced is in the encoding that allows the HD to be broadcast. I believe all the networks use an MPEG2 based encoding scheme that falls into HDV like bitrates, and oddly enough you get very HDVish problems with this type of encoding.
Sooooo... maybe, just maybe there's something a bit broken in the whole MPEG2 lowish bitrate HD thing. I understand they pretty much have to do it this way due to current (and some legacy) equipment, but it'll be nice when the industry moves away from MPEG2 based encoding. Not sure when that will be though.
The great thing (bad thing) about technology is that something newer and better is always just a few years away.
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Old December 25th, 2007, 03:20 AM   #18
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I shoot at 1/1000 all the time unless it starts raining, then I drop to 1/500 and if that's not enough 1/250...

Haven't had to go below that though :)
With such a high shutter speed you have less light, so you have to boost the gain, which leads to a noisy, dirty image. Apart from the fact that a noisy image is uglier, your HDV cam wastes precious bits trying to compress this noise leading to an increase in MPEG2 artifacts. That's further degradation. You'll also have a strobe-like effect even at a 60i or 60p recording or playback rate, which is very distracting. So I can't imagine why you would punish yourself in this manner!
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Old December 25th, 2007, 09:21 AM   #19
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I shoot at 1/1000 all the time unless it starts raining, then I drop to 1/500 and if that's not enough 1/250...
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Originally Posted by Seun Osewa View Post
Apart from the fact that a noisy image is uglier, your HDV cam wastes precious bits trying to compress this noise leading to an increase in MPEG2 artifacts.
Another thing is that DCT compression like MPEG2 tends to look for edges and spends time on them, whilst using a broad brush to wash in areas of flat tone. By using a fast shutter speed, every frame is going to have lots of edges to sharpen. It can't 'hide stuff under the carpet' of a blurred background, say. So the bitrate budget goes almost entirely on edge enhancement rather than hiding those macroblocks.

Sports and water always did kill HDV. As does noise from high gain, but then the Z1 looks very clean with 3dB, and even 6dB isn't intrusive.

I'd give a slower shutter and lots of ND to keep the iris =< f4 a try, but it won't deliver the 'Top Gear' or 'Ryan' effect you're used to seeing. Sometimes one has to adjust style to suit the format.
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Old December 26th, 2007, 01:11 PM   #20
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Originally Posted by Chris Barcellos View Post
On some big time broadcasts I receive over the air, like football games, I will notice some blocking in fast pans. Is it the what's going on in the camera, or is it at the truck at the football stadium, the uplink to sattelite, downlink to the local affiliate, or in how my TV process the signal.... Don't really know, but I know that most of the time, the pictue is spetacular.
Ethan is correct here- it's not your camera. Depending on how you receive your broadcasts, you're looking at an image that's been compressed like there's no tomorrow! An over-the-air broadcaster like a TV station only has so much bandwidth to play with, and on top of that, they don't even USE their full allotment of bandwidth so they have some extra wiggle room in case something goes wrong. Right now, broadcasters output their HD signals at around 18-18.5 mbps, which is a bit lower than the 25mbps for HDV. Some providers, such as cable or satellite, might even use a lower bandwidth. I've even heard a couple engineers talking about trying to send an HD signal through a 10mbps pipeline. That last little bit is only hearsay, so I'm not sure on the overall accuracy of that. But, from my limited experiences, any and all HD material gets compressed like you wouldn't believe before it hits the airwaves.
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Old December 26th, 2007, 04:08 PM   #21
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Ethan is correct here
Can someone please teach that phrase to my wife?
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Old December 27th, 2007, 07:24 AM   #22
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Can someone please teach that phrase to my wife?
Sorry man, that's just too hard... harder than encoding HDV to MPEG2... :)
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Old December 27th, 2007, 09:07 AM   #23
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Sooooo... maybe, just maybe there's something a bit broken in the whole MPEG2 lowish bitrate HD thing. I understand they pretty much have to do it this way due to current (and some legacy) equipment, but it'll be nice when the industry moves away from MPEG2 based encoding.
But note that it's MPEG2 in combination with low bit rates which causes problems, and in spite of that viewers have been content with MPEG2 encoding for almost everything they watch lately (both broadcast and DVD). HDV works fine for the price, and if you need something better the Sony EX1 looks promising for under $10K. Plus you can run HDV cameras in DV mode if desired to avoid HDV encoding issues, for what that's worth.

The only thing likely to replace MPEG2 is MPEG4, which is generally used at even lower bit rates with corresponding encoding perils. Either way you're not likely to see delivery options with bandwidth above ~35 Mbps or non-GOP encoding, so these issues aren't going away any time soon.
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Old December 27th, 2007, 02:22 PM   #24
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You'll also have a strobe-like effect
Yeah I have to say I get a headache just thinking about watching those clips.

Framegrabs from any video footage - even commercial film - always look bad in one way or another. If it isn't artifacts it's motion blur....but then no-one actually watches footage that way .....
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