Biopowered - vegetable oil and biodiesel forum
General => Chatter => Topic started by: Rotary-Motion on March 12, 2013, 11:46:18 AM
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awesome
http://www.youtube.com/watch?v=uENITui5_jU
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A very nice example of aliasing caused by exceeding the Nyquest rate. In this case, his video capture rate must be 24Hz, the same as that of the audio. Very similar to why helicopter blades appear to stand still or reverse in videos.
Certainly looks fantastic with water :)
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A very nice example of aliasing caused by exceeding the Nyquest rate.
My thoughts precisely but who didn't know that anyway? ::)
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So thats a trick of the camera? Shame. It would make am awesome water feature in a garden.
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If it is just a trick of the camera could someone explain the shadow that is cast at the 1 minute point.
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A very nice example of aliasing caused by exceeding the Nyquest rate. In this case, his video capture rate must be 24Hz, the same as that of the audio. Very similar to why helicopter blades appear to stand still or reverse in videos.
Certainly looks fantastic with water :)
aaah the good old nyquest rate. had to study that at 9 am on a monday morning that was when i started drowning in my own ignorance and decided i didnt like DSP as a subject and went back to analogue.[[its s the same effect you get with wheels on cars appearing to go backwards as well.
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If it is just a trick of the camera could someone explain the shadow that is cast at the 1 minute point.
The water is genuinely in the position you can see in the video 24 times a second for a fraction of a second (as is the shadow). What the camera doesn't show is all the all the intervening water positions, that, to the naked eye, would just look like a blur of falling droplets. it just so happens that the water falls through the same shape again and again every 24th of a second.
The difference between the camera 24Hz and the water frequency gives the apparent forward/backward drift in time. It's quite fascinating to watch :)
Strobes are used to observe fast rotating machinery, with the strobe firing at the same (or very near) speed as the rotating part, which makes it appear stationary even though it is moving fast - as the same position is illuminated every time the strobe goes off. It's the same principle with video capture.
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If it is just a trick of the camera could someone explain the shadow that is cast at the 1 minute point.
The water is genuinely in the position you can see in the video 24 times a second for a fraction of a second (as is the shadow). What the camera doesn't show is all the all the intervening water positions, that, to the naked eye, would just look like a blur of falling droplets. it just so happens that the water falls through the same shape again and again every 24th of a second.
The difference between the camera 24Hz and the water frequency gives the apparent forward/backward drift in time. It's quite fascinating to watch :)
Strobes are used to observe fast rotating machinery, with the strobe firing at the same (or very near) speed as the rotating part, which makes it appear stationary even though it is moving fast - as the same position is illuminated every time the strobe goes off. It's the same principle with video capture.
Thanks Tony. ;)
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My day job is R&D for video compression so sorry if that was tmi :)
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r and d?
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r and d?
Research and Development. It's all about squeezing as much video quality as possible out of a given bitrate.
If you watched the Olympics, all of that video was compressed for broadcast with our kit.
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loosing HD quality i guess 1080p/i - 720p/i etc....
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loosing HD quality i guess 1080p/i - 720p/i etc....
Even for just 1080i25, it can be broadcast at different bitrates - 8mbps will look quite good but 1mbps will look awful (even though it's still 1080). Things like grass becoming a smooth green blur rather than showing detail - these are all compression artifacts caused by limited bitrate.