Abstract: In an image recording system for use in recording a sequence of coded signals on a recording medium, such as a CD-ROM in response to a sequence of image signals divisible into a succession of frames each of which is subdivided into a plurality of splits, the image signals are selectively subjected to interframe coding and intraframe coding in a coder to be coded into first and second error signals, respectively, under control of a coding control circuit. The intraframe coding may be carried out about a selected split at every frame, at every preselected period, or at predetermined positions of each scene. The second and the first error signals are rearranged into the coded signals by delaying the second error signal relative to the first error signal. Such a second error signal serves to reproduce an initial image on reproducing the coded signals and enables a reverse reproduction, a quick search, a high speed reproduction, and the like in a reproducing system.

Abstract: In an encoding system responsive to a sequence of coefficient signals which results from a predetermined linear transform and which is divided into a sequence of blocks, anterior processing is carried out prior to quantization about the coefficient signals in each block to determine a significant area of the coefficient signals by comparing each level of the coefficient signals with a threshold level. Only the coefficient signals within the significant area are judged to be valid and produced as a sequence of significant coefficient signals from a classifying circuit (20) to be quantized by a quantizer (15) into a sequence of quantized signals. The quantized signal sequence is subjected to posterior processing to produce a sequence of encoded signals. The significant area may be decided by the use of a selected one of zone detection, zigzag scanning, and adaptive scanning.

Abstract: A system of coding moving image signals produces a predictive error signal by a predictive coding based on inter-frame correlation and quantizing the predictive error signal for each block of a picture frame constituted by N lines of M pixels. The system includes a block coding/non-coding decision unit for calculating a first evaluation value Sm of the predictive error signal for each block of the picture frame. This unit decides that block non-coding is applicable when the first evaluation value Sm is less than a first threshold value T.sub.1 and that block coding is applicable when the first evaluation value Sm is greater than the first threshold value T.sub.1. The predictive error signal is not transmitted when the result of the decision is for block non-coding, and the predictive error signal is quantized and transmitted when the result of the decision is for block coding.

Abstract: In an encoder responsive to a sequence of coefficient blocks each of which is composed of a plurality of orthogonal transform coefficients subjected to predictive encoding and orthogonal transform, the coefficient blocks are classified by a classification circuit (55) into a plurality of classes to produce a control signal (CONT) representative of the classes. A quantization unit (60), a code conversion unit (61), and a coefficient selection unit (62, 64) are controlled by the control signal to select quantization characteristics, code conversion characteristics, and coefficient selection characteristics. The quantization unit comprises a plurality of quantizers corresponding to the quantization characteristics while the code conversion unit and the coefficient selection unit comprise a plurality of code converters and a plurality of selection tables corresponding to the code conversion characteristics and the coefficient selection characteristics, respectively.