Encoding apparatus for motion video signals

An encoding apparatus for encoding input motion video signals by data compression comprising:

• information source coding means, having a built-in quantizer whose input/output characteristics are controlled by a quantization characteristic control signal indicating the relative coarseness of the quantization characteristic in every prescribed period, for subjecting said input motion video signals to source coding;
• converting means for converting the result of information coding by the information source coding means into a variable word length code sequence;
• counter means for counting the number of bits in said variable word length code sequence, resulting from conversion by the converting means, in every said prescribed period;
• quantization characteristic candidate determining means for supplying, on the basis of the count provided by the counter means, a first quantization characteristic candidate signal indicating a quantization characteristic candidate to be used in a next period;
• and
• control means for supplying, on the basis of a value of a preceding quantization characteristic control signal in the period preceding the current period and said first quantization characteristic candidate signal, said quantizer with said quantization characteristic control signal in the current period, and wherein said control means includes,
• a comparator for comparing said first quantization characteristic candidate signal and a second quantization characteristic candidate signal;
• a selector for supplying, in accordance with the result of comparison by said comparator, either said first quantization characteristic candidate signal or said second quantization characteristic candidate signal as said quantization characteristic control signal;
• a delay circuit for delaying said quantization characteristic control signal by a length of time corresponding to one of said every prescribed periods, and supplying the delayed signal as the preceding quantization characteristic control signal of the period preceding said current period;
• and
• a multiplier for multiplying the output of said delay circuit by k (0<k<1) and supplying said second quantization characteristic candidate signal and
• wherein said selector supplies said first quantization characteristic candidate signal as said quantization characteristic control signal when said first quantization characteristic candidate signal is less than said second quantization characteristic candidate signal, and supplies said second quantization characteristic candidate signal as said quantization characteristic control signal when said first quantization characteristic candidate signal is greater than said second quantization characteristic candidate signal.