Friday, February 23, 2007
"B" said I, 1.5 Big ones (Jury rules against Microsoft)
Abstract of US5341457 A technique for the masking of quantizing noise in the coding of audio signals is adapted to include geometric interpolation between the thresholds for a tone masking noise and for noise masking a tone, in order to reduce use of bit-rate capability where it is not necessary for transparent or high quality. The technique is usable with the types of channel coding known as "noiseless" or Huffman coding and with variable radix packing. The stereophonic embodiment eliminates redundancies in the sum and difference signals, so that the stereo coding uses significantly less than twice the bit rate of the comparable monaural signal. The technique can be used both in transmission of signals and in recording for reproduction, particularly recording and reproduction of music. Compatibility with the ISDN transmission rates known as 1 B, 2 B and 3 B rates has been achieved. Claims of US5341457 We claim: ... 10. A storage medium manufactured in accordance with a process comprising the steps of: (a) processing an ordered time sequence of audio signals partitioned into a set of ordered blocks, each said block having a discrete frequency spectrum comprising a first set of frequency coefficients; and (b) for each of said blocks: (1) grouping said first set of frequency coefficients into at least one group, each group comprising at least one frequency coefficient; (2) generating at least one tonality value, each group having an associated tonality value, said at least one tonality value reflecting the degree to which said time sequence of audio signals comprises tone-like quality; (3) generating at least one noise masking threshold, each said at least one noise masking threshold being based upon at least one tonality value; (4) quantizing at least one frequency coefficient in said at least one group resulting in a set of quantized frequency coefficients, said quantizing based upon said at least one noise masking threshold; (5) applying a recording signal to said storage medium, said recording signal comprising signals representing said set of quantized frequency coefficients; and (6) recording said recording signal onto said storage medium.