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Image Compression


A hand held motioncamera's digital images are all different, even when if the camera would be 100% without noise, because even the slightest change of camera position results in a shifted image on the image sensor. Imagine a studio setting where nothing whatsoever is happening. Just standing still with a hand hold motion camera, and shooting in one direction.
Shooting at 25 frames per second at a resolution of 1366*768 pixels, and each pixel being 24 bits. That's 25178112 bits per frame (about 3 MegaByte). Without compression, a one minute shot wil be 25178112*25*60 = 37767168000 bits = about 4502 MegaBytes! While this is crazy because the scene did not change one bit!

All the parts of the scene that do show in the picture, should be saved just once, which at high jpeg quality could be about 1.2 MegaBytes. The ratio between this one jpeg divided by one minute uncompressed = 0.00027
The other things than need to be saved is the chance of image position (relative to the previous frame): horizontal & vertical shift, and degrees of turning.

More complex
There are a lot of camera related variations:
- Horizontal & vertical motion
- Turning
- Angle of view
- Distance of maximum sharpness (relative to the image sensor)
- Depth of field
- Focal length
- Exposure time
All have a lot of influence on how a scene becomes an image on the image sensor, while the scene could be completely without change.
A scene should be stored only once, plus the camera's point of view for each frame (relative to the previous frame of course).

Giesbert Nijhuis

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