Systems and methods for implementing a sample rate converter using hardware and software to maximize speed and flexibility

Abstract

Systems and methods for converting a digital input data stream from a first sample rate to a second, fixed sample rate using a combination of hardware and software components. In one embodiment, a system includes a rate estimator configured to estimate the sample rate of an input data stream, a phase selection unit configured to select a phase for interpolation of a set of polyphase filter coefficients based on the estimated sample rate, a coefficient interpolator configured to interpolate the filter coefficients based on the selected phase, and a convolution unit configured to convolve the interpolated filter coefficients with samples of the input data stream to produce samples of a re-sampled output data stream. One or more hardware or software components are shared between multiple channels that can process data streams having independently variable sample rates.

Description

RELATED APPLICATIONS[0001]This application claims priority to: U.S. Provisional Patent Application No. 60 / 469,761, entitled “Systems and Methods for Implementing a Sample Rate Converter Using Hardware and Software to Maximize Speed and Flexibility,” by Andersen, et al., filed May 12, 2003; U.S. Provisional Patent Application No. 60 / 456,414, entitled “Adaptive Anti-Clipping Protection,” by Taylor, et al., filed Mar. 21, 2003; U.S. Provisional Patent Application No. 60 / 456,430, entitled “Frequency Response Correction,” by Taylor, et al., filed Mar. 21, 2003; U.S. Provisional Patent Application No. 60 / 456,429, entitled “High-Efficiency, High-Performance Sample Rate Converter,” by Andersen, et al., filed Mar. 21, 2003; U.S. Provisional Patent Application No. 60 / 456,421, entitled “Output Device Switch Timing Correction,” by Taylor, et al., filed Mar. 21, 2003; U.S. Provisional Patent Application No. 60 / 456,422, entitled “Output Filter, Phase / Timing Correction,” by Taylor, et al., filed M...

AI Technical Summary

Benefits of technology

[0015]The use of both hardware and software components may provide a number of advantages over prior art systems. One potential advantage is that components for which processing speed is important may be implemented in dedicated hardware to maximize their performance, while other components for which flexibility is more important can be implemented in software. Another potential advantage is that hardware and / or software components may be common to (shared by) multiple channels, thereby reducing the cost and complexity of the system, while retaining the speed and flexibility of the system. Another potential advantage is that each of the channels may be able to handle input sample rates which are variable and which are independent of the sample rates of data streams on other channels. Another potential advantage is that the generation of a local, high-performance clock signal enables the PWM output to meet higher performance standards than if the clock signal must be regenerated from the input data.

Problems solved by technology

More particularly, these attempts utilized analog modulation schemes that resulted in very low performance applications.

These applications were very complex and costly to implement.

Consequently, these solutions were not widely accepted.

Prior art analog implementations of Class D technology have therefore been unable to displace legacy Class AB amplifiers in mainstream amplifier applications.

These digital PWM schemes, however, did little to offset the major barriers to integration of PWM modulators into the total amplifier solution.

Class D technology has therefore continued to be unable to displace legacy Class AB amplifiers in mainstream applications.

There are a number of problems with existing digital PWM modulation schemes.

One of the problems is that the performance and quality characteristics of the remainder of the signal processing system vary with the application.

As a result, implementation details cannot be accounted for apriori.

Because existing technologies require application-specific solutions, they typically are not flexible, scalable or transportable to other applications.

Consequently, these technologies generally are not applicable to mainstream systems.

One area in particular where existing digital PWM modulation schemes do not meet mainstream system requirements is in the processing of digital input data streams having various sample rates.

Existing technologies require a single input sample rate, or multiple fixed, known input rates, and cannot adapt to the different rates at which devices may provide the input data.

Another problem with prior art systems is that, because they do not have a sample rate converter that can generate a local clock signal, they typically regenerate the PWM clock signal from the input data.

This regenerated clock signal cannot support the higher performance that is possible with a locally generated clock signal.

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