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1. WO1997031363 - PC AUDIO SYSTEM WITH FREQUENCY COMPENSATED WAVETABLE DATA

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[ EN ]

What is claimed is:
1. A method of providing a frequency compensated version of a first patch of wavetable data recorded at a first frequency and stored in a memory, wherein said frequency compensated patch is stored in said memory and either said first patch or said frequency compensated patch is accessed from said memory by a digital wavetable audio synthesizer and used to generate digital audio signals having a second frequency which is higher than said first frequency, and wherein digital audio signals generated from said frequency compensated patch have less noise than digital audio signals generated from said first patch, said method comprising the steps of:
(a) accessing said first patch of wavetable data from said memory;
(b) deriving, from said first patch of wavetable data, a patch of wavetable data which represents a digitally filtered version of said first patch of wavetable data and which has a third frequency greater than said first frequency, wherein said derived patch of wavetable data comprises said frequency compensated patch; and
(c) storing said frequency compensated patch in said memory for use by said digital audio synthesizer in generating digital audio signals having said second frequency.

2. A method of providing a frequency compensated patch of wavetable data to reduce system bus bandwidth requirements of a digital wavetable audio synthesizer, wherein said synthesizer provides audio enhancement to a host personal computer of the type including a central processor, a system memory which stores one or more patches of wavetable data recorded at a first frequency, and a system bus, and wherem said synthesizer is programmed to process patches of wavetable data stored in system memory and generate digital audio signals having a second frequency, said method comprising the steps of:
(a) calculating a ratio of said second frequency to said first frequency for a first patch of wavetable data stored in system memory;
(b) accessing said first patch of wavetable data from said system memory if said ratio is greater than a predetermined value;
(c) deriving, from said first patch of wavetable data accessed from system memory, a patch of wavetable data which represents a digitally filtered version of said first patch of wavetable data and which has a third frequency greater than said first frequency, wherein said derived patch of wavetable data comprises said frequency compensated patch; and
(d) storing said frequency compensated patch of wavetable data in system memory for use by said digital wavetable audio synthesizer in generating digital audio signals having said second frequency.

3. The method of claim 2, wherein said predetermined value is greater than about 2.0.

4. The method of claim 3, wherein the ratio of said second frequency to said third frequency is less than or equal to about 2.0.

5 A method of providing a frequency compensated patch of wavetable data to reduce system bus bandwidth requirements of a digital wavetable audio synthesizer, wherein said synthesizer provides audio enhancement to a host personal computer of the type including a central processor, a system memory which stores one or more patches of wavetable data recorded at a first frequency, and a system bus, and wherem said synthesizer is programmed to process patches of wavetable data stored in system memory and generate digital audio signals havmg a second frequency, said method compnsmg the steps of:
(a) calculating a ratio of said second frequency to said first frequency for a first patch of wavetable data stored m system memory,
(b) accessing said first patch of wavetable data from said system memory if said ratio is greater than a predetermmed value;
(c) transposing a fraction of data samples m said first patch accessed from system memory, wherem said fraction of data samples compnses said frequency compensated patch and has a third frequency greater than said first frequency, and
(d) storing said frequency compensated patch of wavetable data in system memory for use by said digital wavetable audio synthesizer m generatmg digital audio signals having said second frequency.

6 The method of claim 5, wherein said predetermined value is greater than about 2.0

7. The method of claim 6, wherem the ratio of said second frequency to said third frequency is less than or equal to about 2.0.