Compression starts within an individual video frame.
Spatial Compression
Each video frame has lots of redundancy in it. Blue sky, grass, walls, furniture, uniforms, and so on. Spatial compression seeks to eliminate this redundancy and save bandwidth by keeping only the key information. For example, a compression system might chop a video frame into 4 pixel by 4 pixel and 8 pixel by 8 pixel blocks of information. If there is blue sky in those blocks, it might not be necessary to include all of the information from each of the 64 pixels. But the information for one pixel could be sent down the line with a code to repeat the same thing for the other 63 pixels. This would eliminate redundancy and reduce bandwidth requirements.
Entropy Reduction
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