Patent ID: 7526030

Claim:
A digital signal conversion method comprising: an inverse orthogonal transform step of carrying out inverse orthogonal transform on an intra-frame coded signal and a forward predictive coded signal, of a digital signal of a first format including an intra-frame coded signal processed by intra-frame coding and a forward predictive coded signal and a bidirectionally predictive coded signal processed by forward and bidirection inter-frame predictive coding along with motion detection; a motion compensation out put generation step of generating a motion compensation output to be added to the partially decoded forwarded predictive coded signal and bidirectionally predictive coded signal on the basis of the conversion output from the inverse orthogonal transform step; an orthogonal transform step of orthogonally transforming the motion compensation output from the motion compensation output generation step; an addition step of adding the orthogonal transform output from the orthogonal transform step to the partially decoded forward predictive coded signal and bidirectionally predictive coded signal; a conversion step of carrying out signal conversion processing on the addition output between the addition step and the coding step, wherein at the coding step, the compression coding processing is carried out on the converted signal from the conversion step; and a coding step of carrying out compression coding on a signal based on the addition output and outputting a digital signal of a second format, wherein at the conversion step, signal conversion is carried out on the output from the addition step by using a transform matrix generated on the basis of an inverse orthogonal transform matrix corresponding to an orthogonal transform matrix used for orthogonal transform coding performed on the digital signal of the first format and an orthogonal transform matrix corresponding to an inverse orthogonal transform matrix used for obtaining the digital signal of the second format.