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Low bit rate transform coder, decoder, and encoder/decoder for high-quality audio

  • US 5,230,038 A
  • Filed: 11/04/1991
  • Issued: 07/20/1993
  • Est. Priority Date: 01/27/1989
  • Status: Expired due to Term
First Claim
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1. An encoder for the encoding of digital information, said digital information comprising signal sample block pairs, each of said block pairs comprising a respective one of a sequence of first signal sample blocks and a respective one of a sequence of second signal sample blocks, said sequence of first signal sample blocks representing a first channel of analog audio signals and said sequence of second signal sample blocks representing a second channel of analog audio signals, comprisingmeans for generating subband information block pairs in response to said signal sample block pairs by applying a function substantially corresponding to the alternate application of a modified Discrete Cosine Transform function and a modified Discrete Sine Transform function in accordance with the evenly-stacked Time-Domain Aliasing Cancellation technique, each of said subband information block pairs comprising a first subband information block and a second subband information block, said means comprisingmeans for multiplying real valued signal samples in the signal sample block pairs by a first complex function to obtain complex-valued modified signal sample sets,means for applying a Fast Fourier Transform concurrently against said complex-valued modified signal sample sets, andmeans for multiplying the results of the transformation by a second complex function to obtain said subband information block pairs, each first subband information block comprising a first set of digital words, and each second subband information block comprising a second set of digital words, andmeans for quantizing said digital words.

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