초록 ▼

A digital video compression system and its methods for compressing digitalized video signals in real time at rates up to NTSC color broadcast rates are disclosed. The system compressor receives digitalized video frames divided into subframes, performs in a single pass a spatial domain to transform d

A digital video compression system and its methods for compressing digitalized video signals in real time at rates up to NTSC color broadcast rates are disclosed. The system compressor receives digitalized video frames divided into subframes, performs in a single pass a spatial domain to transform domain transformation in two dimensions of the picture elements of each subframe, normalizes the resultant coefficients by a normalization factor having a predetermined compression ratio component and an adaptive rate buffer capacity control feedback component, to provide compression, encodes the coefficients and stores them in a first rate buffer memory asynchronously at a high data transfer rate from which they are put out at a slower, synchronous rate. The compressor adaptively determines the rate buffer capacity control feedback component in relation to instantaneous data content of the rate buffer memory in relation to its capacity, and it controls the absolute quantity of data resulting from the normalization step so that the buffer memory is never completely emptied and never completely filled. In expansion, the system essentially mirrors the steps performed during compression. An efficient, high speed decoder forms an important aspect of the present invention. The compression system forms an important element of a disclosed color broadcast compression system.

대표청구항 ▼

A method for one pass compressing, transferring through a medium and expanding in real time digitalized television video frames, the compression steps comprising: (a) dividing each digitalized frame into a predetermined matrix of sub-frames; (b) performing a predetermined spatial domain to transform

A method for one pass compressing, transferring through a medium and expanding in real time digitalized television video frames, the compression steps comprising: (a) dividing each digitalized frame into a predetermined matrix of sub-frames; (b) performing a predetermined spatial domain to transform domain transformation in two dimensions of the picture elements of each sub-frame to provide transform coefficients thereof; (c) storing said transform coefficients in a memory at a rate related to the video frame rate; (d) normalizing said transform coefficients by operation of a normalization factor having a predetermined compression ratio component to perform threshold coding of said transform coefficients and an adaptive rate buffer capacity control feedback component, to provide compression and to provide normalized transform coefficients compatible with a predetermined data coding scheme including Huffman coding of amplitude coefficients and run length coding of zero amplitude coefficients following coefficient normalization; (e) coding said normalized transform coefficients in accordance with said predetermined data coding scheme for further compression and transfer through said limited bandwidth medium; (f) loading said coded coefficients into an encode rate first in, first out buffer memory asynchronously at a high data transfer rate; (g) unloading said coded coefficients from said encode rate buffer memory at a slow data transfer rate capable of passing through said limited bandwidth medium; and (h) adaptively determining said rate buffer capacity control feedback component in relation to the instantaneous data content of said rate buffer memory in relation to its capacity, to control at said normalization step the absolute quantity of data resulting therefrom so that said rate buffer memory is never completely emptied and never completely filled, and combining said feedback component with said compression ratio component to provide said normalization factor; and, the expansion steps comprising: (i) loading said coded coefficients into a decode rate first in, first out buffer memory at said slow synchronous data transfer rate; (j) unloading said coded coefficients from said decode rate buffer memory asynchronously at a high data transfer rate; (k) decoding said coded coefficients in accordance with an inverse of said predetermined data coding scheme; (l) inversely normalizing said decoded transform coefficients by operation of an inverse normalization factor having a predetermined expansion ratio component and an adaptive decode rate buffer capacity control feed forward component, to provide expansion of said transform coefficients; (m) adaptively determining said rate buffer capacity control feed forward component in relation to said instantaneous data content of said decode rate buffer memory in further relation to its capacity so as to control at said inverse normalization step the absolute quantity of data resulting therefrom and thus the rate at which said coded coefficients are unloaded asynchronously from said decode rate buffer memory so that it is never completely emptied and never completely filled, and combining said feed forward component with said expansion ratio component to provide said inverse normalization factor; (n) performing the inverse of said predetermined transformation of said expanded transform coefficients to provide reconstituted picture elements of each sub-frame; (o) assembling said sub-frames into said predetermined matrix and putting them out at said video frame rate so as to reconstruct digitalized picture frames closely approximating the corresponding original video frames.