| 摘要 |
PURPOSE:To attain optimum code quantity distribution even to various input pictures by sequentially revising a quantization step width of each band based on a difference between an input picture signal and a local decoding signal. CONSTITUTION:After an input picture signal is divided into 1/2 in the horizontal direction by horizontal direction sub band filters 2, 3, and vertical direction sub band filters 4-7 are used to divide the signal into 1/2 in the vertical direction, then a signal HH with high frequency in the horizontal and vertical directions, a signal HL with a high frequency in the horizontal direction and a low frequency in the vertical direction, a signal LH with a low frequency in the horizontal direction and a high frequency in the vertical direction, and a signal LL with a low frequency in the horizontal and vertical directions are outputted. Then coders 8-11 quantizes the data and the result is outputted to an entropy coder 12 and part of quantized data is locally decoded and a square of a coded error with a difference from the input signal is obtained and outputted to a control signal generator 15. The ratio of a step width of quantization of each band is revised depending on the magnitude of square mean value of the coded error to execute code quantity distribution control. Thus, optimum code quantity distribution is attained even to various input pictures. |
