To provide a rate converting method and device capable of suppressing deterioration in the image quality even in the presence of a rapid change in a code quantity.
The rate converter converts first image coded data comprising a plurality of images into second image coded data with a desired bit rate by applying variable length decoding, inverse quantization, re-quantization, variable length coding, and multiplexing to the first image coded data, and includes: a rate control means for controlling a code quantity assigned to each of pictures in response to rate conversion contents and controlling parameters at re-quantization on the basis of the code quantity; and an MB type analysis means for analyzing incident rates of each of macro block (MB) types, and the rate control means varies an assigned code quantity in response to the incident rate of each type analyzed by the MB type analysis means and adjusts the code quantity assigned to the other pictures to make the code quantity constant.
HAMAMOTO YASUO
HAYASHINO YUJI
Tomoyasu Sakaguchi
Hiroki Naito
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