Fractional Digital Delay Lines With Interpolated Write Pointer Control
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Solution Overview
Problem
Digital delay lines in audio signal processing face challenges with high latency and burst data transfer characteristics, requiring efficient methods to minimize latency and optimize access to delay lines with minimal access delay, especially in systems that need multiple delay lines for DSP algorithms.
Innovation Solution
The implementation of a fractional delay line system using a method and device that modulates the write pointer in delay lines, allowing for fractional delay lengths by interpolating between adjacent samples, and utilizing a primary and secondary cache arrangement to manage data access efficiently, reducing the need for abrupt changes in delay line lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional digital delay lines are used with integer sample periods, then the implementation is simple with direct memory access, but the latency is high and fractional delay lengths cannot be achieved
Solution Approach 1:
The delay line is segmented into integer delay components (handled by conventional memory access) and fractional delay components (handled by interpolation). This allows the system to maintain simple integer-based memory access while adding fractional delay capability through separate interpolation logic, reducing overall access delay without requiring complete redesign of the delay line structure.
Solution Approach 2:
An interpolation mechanism acts as an intermediary between the integer sample periods stored in memory and the desired fractional delay output. This intermediary component processes the stored samples to generate fractional delay values, enabling precise delay control without increasing the fundamental memory access structure or latency of the underlying delay line.
2Adaptability or versatility
If multiple delay lines are provided for DSP algorithms, then the algorithm support is enhanced, but the number of read and write accesses increases significantly
Solution Approach 1:
Multiple delay lines are merged into a single shared memory structure with multiple read/write pointers. This allows different DSP algorithms to access different portions of the same memory block simultaneously, reducing the total number of memory accesses required while maintaining support for multiple algorithms. The shared structure eliminates redundant storage and access operations.
Solution Approach 2:
A single delay line memory structure is designed to serve multiple DSP algorithms simultaneously through the use of multiple independent pointers. Each algorithm can configure its own read and write pointers to access the appropriate delay lengths, making the delay line universal and adaptable to various algorithm requirements without requiring separate dedicated memory blocks for each algorithm.
3Adaptability or versatility
If the delay line length is changed abruptly, then the system can adapt to different delay requirements, but audio artifacts are introduced
Solution Approach 1:
The delay line length is changed dynamically and continuously rather than abruptly. The system uses fractional delay interpolation to smoothly transition between different delay lengths, adjusting the delay in small incremental steps. This dynamic adjustment process maintains audio quality by avoiding sudden changes that would introduce artifacts, while still providing adaptability to different delay requirements.
Solution Approach 2:
The system prepares for delay length changes by using interpolation to cushion the transition. Before and during delay length adjustments, the interpolation mechanism pre-calculates and smoothly blends the transition between delay values, preventing abrupt changes that would cause audio artifacts. This cushioning effect ensures continuous, artifact-free audio output during delay reconfiguration.
Data Source
AI summary
Embodiments of a signal processing system, a method, and fractionally modulated digital delay lines are generally described herein. Other embodiments may be described and claimed. In some embodiments, a fractional address is generated by adding a delay value to a fractional offset value, and input sample values are interpolated based on a fractional portion of the fractional address. A write operation may be performed to the integer portion of the fractional address for each sample period using the interpolated input sample values. Adjusted addresses may be generated when addresses are either skipped of duplicated.