Method for reducing the image data of digital television signals

Claim 1

Method for reducing the image data of digital television signals, including preprocessing of the signals by means of a block-by-block transformation process, in which, in the preprocessing, both a transformation and the formation of a difference between a signal which was generated at a time t-1 and stored in a frame buffer, and a signal which is produced at a time t, are carried out so that the preprocessing forms a transformed frame-to-frame prediction error signal, the prediction error signal formed in this manner being subjected to a scalar quantization, in which a number No is determined from the quantized prediction error signal, which number corresponds to the secondary diagonal parallel in a coefficients matrix, up to which, starting from a DC component, significant coefficients are contained, and which number is used for reducing the number of the coefficients to be transmitted, which number No is also transmitted, characterized - in that the prediction error signal is also subjected to a vector quantization in a manner known per se and the representative block selected as a result is transmitted indirectly by its index which represents its address in a code book, and the representative block is subtracted from the quantized prediction error signal in order to achieve by this means a reduction in the energy of the signal to be transmitted, - in that an absolute amount of the transformed input signal is formed by eliminating the sign in order to be able to carry out a more efficient vector quantization, - in that the signs for coefficients having a value not equal to zero are transmitted separately from the amounts of the coefficients, - in that a classification of the block of transformation coefficients is carried out for the purpose of selecting one of a multiplicity of code books in association with a reduction in the number of code books by transposing the input signal block to a smaller necessary number of code books, - in that a Huffman table correlation is carried out with the aid of the class found, - in that a scalar quantization is carried out both of the representative block and of the prediction error signal and is controlled by the vector quantizer index (CVQ), by the class (KVQ) and by a buffer memory control signal (QBC), - in that the selected representative block is used for defining (Figure 8) an area A v which is used for achieving, in a combination with an area AN defined by the number N D , an effective description of an area A TC , of an area A TV , in which signs are transmitted and in which significant coefficients are contained, - in that this area A v is given by the fact that the coefficients of the representative block which was selected from the code book have a value not equal to zero, and - in that an area selector (Figure 9), which can have a value between 0 and 3 (Figure 9), is transmitted which defines how the areas Arc and A TV are formed from the areas AN and A v .