Patent ID: 8780977

Claim:
A transcoder for converting a first stream into a second stream, comprising: a bit rate acquisition device configured to acquire an average bit rate S k (k is a natural number) of a first stream in a control unit time L k ; a buffer configured to store average bit rates S n , S n−1 , . . . , S n−m+1 (M and n are natural numbers, n>M) obtained in control unit times L n , L n−1 , . . . , L n−M+1 , respectively, of the first stream in a plurality of past periods corresponding to a plurality of the control unit times, the average bit rates being acquired by the bit rate acquisition device; a reference value calculation device configured to determine a period within the plurality of past periods, the determined period corresponding to P control unit times composed of control unit times L n , L n−1 , . . . , L n−p+1 (P is a natural number, P<M), as a selected period, and the reference value calculation device further configured to acquire average bit rates S n , S n−1 , S n−P+1 of the first stream in the selected period from said buffer to calculate a reference value for a bit rate of the first stream in said selected period based on the average bit rates S n , S n−1 , . . . , S n−P+1 ; and a quantization step value calculation device configured to calculate a quantization step value of the second stream by including said reference value of bit rates of the first stream in said selected period which is calculated by said reference value calculation device as a parameter.