Signal encoding and decoding method and device

DETAILED DESCRIPTION It is an object of the present invention to provide a method and device for encoding and decoding signals, which are fit for human visual and auditory characteristics, and which are adapted to reduce the information content necessary for transmitting and storing an image or audio signal.
To achieve the above object, the present invention resides in a method of encoding and decoding image and audio signals, any of the signals being subjected to sampling and having a multiplicity of sampling points each represented by a quantized amplitude value.
An encoding step comprises the steps of: transmitting an amplitude value of a given sampling point as an initial value; subtracting the initial value from each of amplitude values of n sampling points (where n is a predetermined integer) to calculate n difference values therebetween, and calculating positive or negative signs, which respectively indicate varying directions of the amplitudes imposed by the difference values with respect to the initial value and absolute values of the difference values; previously preparing a quantization table which has threshold values and representative values expressed in terms of amplitude values, defines an ordered set of n quantization scales (where n is a predetermined integer) each comprising at least one threshold value and a representative value, and also defines index values different from one another for all the representative values of said n quantization scales; comparing a series of n difference absolute values with a series of n quantization scales included in the quantization table sequentially from the sampling point adjacent to the initial value until the maximum n-th sampling point, and selecting a representative value of the most suitable quantization scale; transmitting the index value of the selected representative value of the quantization scale and the positive or negative sign; and repeating the foregoing steps with the sum of the selected representative value of the quantization scale and the current initial value being set as a subsequent initial value