To encode a bit stream before conversion so that a code quantity of a bit stream after conversion is kept within a prescribed code quantity in the case that a digital video signal is compressed by a prescribed method and the compressed signal is converted into a video signal adopting the other compression method.
A quantizer is selected, in which both code quantities resulting from applying 1st and 2nd variable length coding to an AC component of an input digital video signal receiving discrete cosine transform becomes the differential code quantities or less, which quantities are the difference between a maximum additional information quantity which is larger in an information quantity of 1st and 2nd additional information sets and a maximum DC code quantity which is larger in a quantity resulting from applying differential prediction coding to a DC component of the discrete cosine transformed input digital video signal and a quantity resulting from applying fixed length coding to the DC component, the selected quantizer quantizes the AC component of the digital video signal that is discrete cosine transformed, the DC component and the 1st additional information are added to the quantized result to generate a 1st bit stream.
NISHINO SHOICHI
MIYASHITA MITSUHIRO
