| 摘要 |
Video signal processing apparatus in which at least two input video signals are combined in proportions determined by a pixel key signal to generate an output video signal for compression, at least one of the input video signals each having respective associated compression parameters from a data compression process applied to that video signal; comprises:means for detecting an average pixel key signal value across each of a plurality of blocks of pixels of the output video signal; andmeans for comparing the average pixel key signal values with first and second thresholds, the first threshold representing a pixel key signal value corresponding to combination having primarily one of the video signals, and the second threshold representing a pixel key signal value corresponding to combination having primarily the other of the video signals;in which:if the average pixel key signal value for a block lies between the first and second thresholds, that block of the output video signal is compressed using newly derived compression parameters; andif the average pixel key signal value for a block lies outside the range defined by the first and second thresholds, the compression parameters associated with the corresponding block of the input video signals are made available for re-use in compression of that block of the output video signal.
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