HIERARCHICAL ENCODING METHOD AND DEVICE

摘要

PROBLEM TO BE SOLVED: To reduce the deterioration of picture quality against a low bit rate in particular by performing no encoding of the color difference signal in a high hierarchy as long as the color difference signal has the satisfactory quality in a low hierarchy and applying the encoding value of the color difference signal to the brightness signal. SOLUTION: The brightness and color difference signals of an image of a low hierarchy are encoded as conventional and a bit stream is produced. When an image of a high hierarchy is processed, the encoded image of the low hierarchy is decoded again via a decoding circuit 22 and an up-sampling circuit 30 up-samples the decoded image on every screen. A detection circuit 42 compares the color difference signal of the high hierarchy image to be inputted with the color difference signal of the image of a low hierarchy that is up-sampled, so that an SNR(signal-to-noise ratio) is decided. If this SNR is larger than a set reference SNR 44, a decision circuit 46 decides that the desired quality is satisfied only by the color difference signal of the low hierarchy. Thus the color difference signal of the high hierarchy is not transmitted through a control circuit 48 and disused. If the SNR is smaller than the SNR 44, the color difference signal or the high hierarchy is encoded by an encoding circuit 34.