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Legitimate values of pixel block brightness are in the range from 0 to 225. The block becomes a part of the delta frame, by default, if the difference between its average brightness in the current frame and in the previous key frame exceeds seven units. Increasing the value of this parameter allows reducing the size of the delta frame and, hence, the size of the video stream, by reducing the number of pixel blocks in the delta frame. Note that the blocks with useful motion data now are more likely to be excluded from the processed video, which consequently leads to video degradation. Reducing the value of the parameter that sets the criterion for including blocks in a delta frame allows improving the video quality by increasing its size.

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