| 摘要 |
PROBLEM TO BE SOLVED: To improve the entire image quality of a video frame signal by conducting adjustment of roughness and fineness of quantization adaptively depending on an input signal activity. SOLUTION: A quantizer control block 110 receives a difference signal of an output of a subtractor 50 and a coded signal outputted from a VLC block 70 to decide a quantization mode signal. Then a quantizer 2 classifies transformation coefficients included in a block into low frequency and high frequency transformation coefficients depending on the quantization mode signal, applies quantization to the low frequency coefficients according to a conventional method and divides the high frequency coefficients before the quantization for more rough quantization purpose. Then the quantizer 12 applies quantization to the low frequency transformation coefficients and the high frequency coefficient divisions based on a quantization step size obtained by multiplying a quantization parameter QP outputted from a quantization parameter decision block 90 and each element in a matrix for a basic quantization step size. As a result, rough/fine quantization is conducted adaptively based on the quantization mode signal. |
