| 摘要 |
A constant luminance corrector for a television system determines brightness information that is discarded in the chrominance channels of an encoder, and adds it to the luminance channel of the encoder. Gamma-corrected luminance and chrominance component signals from a video source, such as a video camera, video tape recorder or the like, are input to the encoder which outputs an encoded luminance component signal and an encoded chrominance component signal that are combined to form a composite signal. The gamma-corrected component signals also are input to a luminance predictor circuit, or alternatively in lieu of the gamma-corrected chrominance component signals a coded chrominance signal and a discarded chrominance signal from the encoder may be input to the luminance predictor circuit. Likewise the encoded luminance component signal may be input to the luminance predictor circuit in lieu of the gamma-corrected luminance component signal. From these signals the luminance predictor circuit produces an ideal and an actual luminance component signal for comparison. A luminance correction signal, representing the lost brightness information, is produced from the difference between the ideal and actual luminance component signals. The luminance correction signal is input to the luminance channel of the encoder for combination with the gamma-corrected luminance signal to restore the brightness lost in the chrominance channels to the luminance channel.
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