Utah State University

Richard W Harris

Paul D Israelsen

Scott Ezra Budge

Chien-Min Huang

A fixed quality source coder receives and performs VQ on an input signal I.sub.D. The signal I.sub.D may be characterized by the number of samples/frame and bits per sample, and may be provided by a traditional source coder. The traditional source coder may include a sample-and-hold (S/H) circuit producing rxs samples/frame and an ADC providing n bits per pixel. In a first embodiment, the number of bits/sample is increased. In the second embodiment, the number of samples/frame is increased. In a third embodiment, both the number of bits/sample and the number of samples/frame are increased. Measurements made in simulations involving the first and second embodiments show that the fixed quality source coder has a smaller data rate, mean absolute error (MAE) and root mean square error (RMSE) than that of the traditional source coder, while maintaining the same or less maximum error. The fixed quality source coder includes an encoder and may also include a decoder. The encoder may include a lossy codec that receives and encodes the signal I.sub.D to provide encoded information to a multiplexer regarding the signal I.sub.D. The lossy codec also decodes the encoded signal to produce a decoded signal I.sub.VQ.sup.-1. A summer receives I.sub.D and I.sub.VQ.sup.-1 and determines an error signal E.sub.R, where E.sub.R may equal I.sub.D -I.sub.VQ.sup.-1. A threshold circuit receives the signal E.sub.R and passes a threshold signal E.sub.T, where a threshold level T may be set to ensure that the maximum error allowed in the encoder is equal to a particular desired maximum error.

Fixed quality source coder with fixed threshold

Apparatus for compressing data is disclosed in which input data is compressed by a vector quantization process and decoded by the vector quantization process. The input data and the decoded input data are compared and a difference signal as produced. A portion of the difference signal is preferably losslessly compressed and transmitted with the vector quantized input signal to a decoder over a communication channel. The decoder decodes the vector quantized portion of the signal and the compressed difference signal for reconstructing the input signal with an error which is less than that which would result from uncompensated vector quantization.

Method and apparatus for data compression with reduced distortion

Post-quantization processing is disclosed in which frames of data are organized into frames of input vectors. For each input vector, the quantizer identifiers a closely matching codebook vector. The quantizer generates a compressed signal by replacing each input vector in a frame with an ID code of a closely matching codebook vector. On subsequent frames, the quantizer further processes ID codes to achieve additional compression. In one embodiment, the ID codes from one frame are compared to the corresponding ID codes in the previous frames. If the ID code from the subsequent frame (new ID code) is the same as the corresponding ID code from the previous frame (old ID code), the new ID code is eliminated from the frame and a tag bit is set to indicate that the ID Code was eliminated. Similarly, if the new ID code represents a vector which is only slightly different from the vector represented by the old ID code, the new ID code is replaced with a tag bit. In this way, transmission of the subsequent frames requires only the transmission of vectors which differ by a significant amount from the prior frame. In other embodiments, other post processing methods are used. For example, lossless coding techniques, such as the socalled Lempel-Ziv and Huffman codes are discussed.

Growing community of inventors

Logan, UT, United States of America

Richard W Harris