Transcoder for coded video

Abstract

Provided is a transcoder for coded video the encoding mode of that is changed according to the coded data, itself, that has been compressed by transcoding, or information prepared by decoding only a part thereof. A coded data extractor partially decodes DV coded data (a) that has been input, and sends DCT coefficients (b) to an approximate image generator and to a decoder, and outputs quantization parameters (c) to a first motion vector detector. The approximate image generator generates an approximate image according to a part of the DCT coefficients (b). A first motion vector detector roughly detects motion vector candidates (e). A second motion vector detector, using the motion vector candidates (e) as an initial position, hierarchically detects a motion vector (f). A re-encoder encodes the data into one the encoding mode of that is new, according to a luminance signal (h) that has been decoded in the decoder, the chrominance signal (j) the data format of that has been transcoded in a sampling format transcoder, and the motion vector (f) that has been detected in the second motion vector detector.