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Abstract

Video encoding and decoding methods and devices are provided which can efficiently switch a lossy mode and a lossless mode to each other. The video encoding device includes: a prediction section that generates a residual signal which is a difference between an input image and prediction values acquired by performing one or more of temporal prediction and spatial prediction on macro blocks of the input image; a transformation and quantization section that performs or skips transformation and quantization on the residual signal depending on mode information; an entropy-coding section that entropy-codes the residual signal output from the transformation and quantization section to generate a bitstream; a lossless-mode QP range determining section that determines a lossless-mode QP range using an amount of bits generated by the entropy-coding section and a quantization coefficient (QP); and a mode determining section that compares a current QP value with the determined lossless-mode QP range to determine one of a lossy mode and a lossless mode and transmits information on the determined mode to the transformation quantization section. Accordingly, by designating a lossless-mode quantization coefficient range, it is possible to reduce an amount of bits necessary for switching a lossy mode and a lossless mode.

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