| 摘要 |
<p>PURPOSE:To improve the picture quality of the whole screen by detecting a case wherein a brightness signal whose visual deterioration is inconspicuous is large and a case wherein the signal is small. CONSTITUTION:This orthogonal transformation and encoding device is equipped with an input terminal 10 where a block-divided image signal is inputted, an orthogonal transformer 11 which performs orthogonal transformation, a quantization control circuit 12 which outputs a control signal for quantization control with the amplitude value of the DC component of an orthogonal transformation coefficient outputted by the orthogonal transformer 11, an encoder 13 consisting of a rearranging means 20, a quantizer 21, a quantization selecting circuit 22, and an encoding circuit 23, and an output terminal 14 where the encoded signal output of the encoder 13 is outputted. Then the quantization control circuit 12 detects the case (close to pure white) wherein the brightness signal whose visual deterioration is inconspicuous is large and the case (close to deep dark) wherein the brightness signal is small from the DC component of the orthogonal transformation coefficient and controls the step width of the quantization by the quantization selecting circuit 22. Consequently, deterioration in the picture quality of the whole screen is reducible.</p> |
