| 摘要 |
A vector quantization method and apparatus which processes signal vectors constructed from digital image data (such as a digital video stream). The digital video stream is treated as a sequence of images, each represented by a rectangular array of pixels. The pixels are processed in blocks (typically 4x4 blocks) of two types, known as smooth blocks and detail blocks. The detail blocks contain the original image pixels, while the smooth blocks contain pixels from a subsampled version of the image. The pixels in the blocks are formatted into image vectors, again in two types. Each type of image vector is separately compressed using a vector quantization coder and a separate code book for each type. Smooth image vectors are compressed using a smooth code book and detail image vectors compressed using a detail code book. The compressed data stream is specially constructed, as a stream of code words for smooth and detail image vectors, updates to the code books, and mask bits that select the type of each code word, to facilitate real time decompression on low cost microprocessors. The coding operation can include interframe coding in which the mask bits are additionally coded so that, in addition to selecting the type of each code word, they also indicate that a block does not change from the last frame and the corresponding code word has been omitted. The inventive compression technique results in a high quality video playback with a high compression ratio (typically about one bit per pixel). This allows high quality compressed video to be played back from conventional CD-ROMs or hard disks, and to be transmitted over communications channels with data rates of 1.5 Mbit/sec.
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