Data processing: generic control systems or specific application – Specific application – apparatus or process – Digital audio data processing system
Reexamination Certificate
2005-05-10
2005-05-10
Harvey, Minsun Oh (Department: 2644)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Digital audio data processing system
C381S101000
Reexamination Certificate
active
06892103
ABSTRACT:
Digital audio tone control implemented using Shelving filters for the digital audio treble tone control exhibits artifacts (noise, distortion, etc.) as the tone control settings are changed. This was previously accomplished by changing filter coefficients in the traditional small equal (on a dB scale) filter steps of a fraction of 1 dB. While this worked for bass filters, artifacts were still present for treble. This invention eliminates these artifacts by changing the filter steps to small equal steps on a linear scale. Additionally, where the steps became too large for the resolution required, additional filter steps are added. Approximately 150 filter steps are used for treble control and 128 filter steps are used for bass tone control. An efficient way of implementing the filter steps for digital tone control stores (119) one set of filter coefficient values and a small amount of additional information and then increments the coefficients between all the other steps. This reduces the memory required by as much as 95% or the machine cycles for implementing filter coefficients by 40-200 times. This new efficient method is accomplished by: 1) defining the filter coefficients, 2) piecewise linearizing the plot of filter coefficients versus filter step to define the linear regions, 3) defining the initial set of filter coefficients, and 4) defining increments between the filter steps.
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Yinong Ding, et al., “Filtering Morphing of Parametric Equalizers and Shelving Filters for Audio Signal Processing”,J. Audio Eng. Soc.., vol. 43, No. 10, 1995 Oct., pp. 821-826.
J.N. Mourjopoulos, et al., “Theory and Real-Time Implementation of Time-Varying Digital Audio Filters”,J. Audio Eng. Soc., vol. 38, No. 7/8, 1990 Jul./Aug., pp. 522-537.
Udo Zoelzer, et al., “Strategies for Switching Digital Audio Filters”, Presented at the 95th Convention of the Audio Engineering Society on Oct. 7-10, 1993, New York.
Allred Rustin W.
Tsecouras Michael J.
Young, Jr. Robert S.
Bassuk Lawrence J.
Brady W. James
Harvey Minsun Oh
Pendleton Brian
Telecky , Jr. Frederick J.
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