System for compression and decompression of video data using discrete cosine transform and coding techniques

A system for data compression and decompression, comprising:

• video interface means for receiving and transmitting digitized images;
• discrete cosine transform means for performing, during data compression, a 2-dimensional discrete cosine transform on data received by said video interface means, and providing coefficients of said 2-dimensional discrete cosine transform, and for performing, during data decompression, a 2-dimensional inverse discrete cosine transform, and providing as output data said coefficients of said 2-dimensional inverse discrete cosine transform to said video interface for transmission as digitized images;
• quantization means for attenuating, during data compression, higher frequency coefficients of said 2-dimensional discrete cosine transform, and for partially restoring, during data decompression, said higher frequency coefficients of said 2-dimensional discrete cosine transform, in preparation for said 2-dimensional inverse discrete cosine transform;
• zig-zag means for rearranging, during data compression, said coefficients of said 2-dimensional discrete cosine transform from "sequential" order into "zig-zag" order, and for rearranging, during data decompression, said zig-zag ordered coefficients of said 2-dimensional discrete cosine transform from a "zig-zag" order to a "sequential" order;
• data packing and unpacking means for packing, during data compression, said "zig-zag" ordered coefficients of said 2-dimensional discrete cosine transform as run length-represented coefficients of said 2-dimensional discrete cosine transform, and for unpacking, during data decompression, said run length-represented coefficients of said 2-dimensional discrete cosine transform to said "zig-zag" ordered coefficients of said 2-dimensional discrete cosine transform;
• Huffman coding/decoding means for coding, during data compression, said run length-represented coefficients of said 2-dimensional discrete cosine transform into Huffman codes, and for decoding, during data decompression, said Huffman codes into said run length-represented coefficients of said 2-dimensional discrete cosine transform;
• first-in first-out memory means for temporary storage of said run length represented coefficients of said 2-dimensional discrete cosine transform such that said Huffman coding/decoding means operates asynchronously and independent of said data packing and unpacking means;
• and
• host interface means for transmitting, during data compression, said Huffman codes to a host computer, and for retrieving, during data decompression, said Huffman codes from a host computer;
• wherein said first-in first-out memory means provides a plurality of status signals indicating the usage of said first-in first-out memory means, and wherein said system further comprises adaptive control means for varying compression ratios achieved on said digitized images during compression according to said status signals.

A method for data compression and decompression, comprising:

• providing a video interface means for receiving and transmitting digitized images as a stream of composite pixels, each composite pixel being data of a plurality of chrominance and luminance component types;
• providing block memory means for receiving and sorting, during data compression, said stream of composite pixels from said video interface means into single-component type data blocks, and for receiving and reconstituting, during data decompression, single-component type data blocks into said stream of composite pixels;
• providing a discrete cosine transform means for performing, during data compression, a 2-dimensional discrete cosine transform on single-component type data blocks received from said block memory means, and providing coefficients of said 2-dimensional discrete cosine transform, and for performing, during data decompression, a 2-dimensional inverse discrete cosine transform, and providing as output data said coefficients of said 2-dimensional inverse discrete cosine transform to said block memory means as single-component type data blocks;
• providing a quantization means for attenuating, during data compression, higher frequency coefficients of said 2-dimensional discrete cosine transform, and for partially restoring, during data decompression, said higher frequency coefficients of said 2-dimensional discrete cosine transform, in preparation for said 2-dimensional inverse discrete cosine transform;
• providing a zig-zag means for rearranging, during data compression, said coefficients of said 2-dimensional discrete cosine transform from "sequential" order into "zig-zag" order, and for rearranging, during data decompression, said zig-zag ordered coefficients of said 2-dimensional discrete cosine transform from a "zig-zag" order to a "sequential" order;
• providing a data packing and unpacking means for packing, during data compression, said "zig-zag" ordered coefficients of said 2-dimensional discrete cosine transform as run length-represented coefficients of said 2-dimensional discrete cosine transform, said run length-represented coefficients of said 2-dimensional discrete cosine transform represent runs of zero coefficients as run lengths of zero coefficients, and for unpacking, during data decompression, said run length-represented coefficients of said 2-dimensional discrete cosine transform to said "zig-zag" ordered coefficients of said 2-dimensional discrete cosine transform;
• providing a Huffman coding/decoding means for coding, during data compression, said run length-represented coefficients of said 2-dimensional discrete cosine transform into Huffman codes, and for decoding, during data decompression, said Huffman codes into said run length-represented coefficients of said 2-dimensional discrete cosine transform;
• providing a first-in first-out means for temporary storage of said run-length represented coefficients of said 2-dimensional discrete cosine transform such that said Huffman coding/decoding means operates asynchronously and independent of said data packing and unpacking means;
• and
• providing a host interface means for transmitting, during data compression, said Huffman codes to a host computer, and for retrieving, during data decompression, said Huffman codes from a host computer.