Patent ID: 8615040

Claim:
A transcoder for converting a first stream into a second stream, comprising: a conversion value calculation processing unit configured to calculate a quantization step conversion value of said first and second streams from a ratio of bit rates of said first and second streams; and a quantization step value calculation processing unit configured to calculate a quantization step value of said second stream by multiplying a quantization step value of said first stream by said quantization step conversion value, wherein said conversion value calculation processing unit is further configured to calculate said quantization step conversion value from said ratio of bit rates by using an area specification function f 0 (x) for specifying an area to which a relation between said ratio of bit rates and said quantization step conversion value belongs and a relation determining function f 1 (x) for determining a specific relation between said ratio of bit rates and said quantization step conversion value in said area, and determine whether a difference between said quantization step conversion value calculated for a current bit rate ratio using said area specification function f 0 (x) and said quantization step conversion value calculated for said current bit rate ratio using said relation determining function f 1 (x) exceeds a predetermined threshold value.