Note-Based Audio to PCM Conversion Lookup Table
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Solution Overview
Problem
Electronic communication devices face delays in converting note-based audio formats to PCM-based formats due to the need for extensive floating point mathematical calculations, especially when they lack a floating point unit (FPU).
Innovation Solution
Incorporating a lookup table with trigonometric function evaluations to generate PCM values for each sample point based on note frequency information, minimizing the need for floating point operations by using interpolation and bit-shift operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If floating point mathematical calculations are performed for conversion, then conversion accuracy is maintained, but conversion time increases significantly
Solution Approach 1:
The patent pre-calculates and stores trigonometric function values (sine and cosine) in lookup tables during system initialization or manufacturing. These pre-computed values are stored in memory for rapid retrieval during audio conversion operations, eliminating the need for real-time floating point trigonometric calculations and significantly reducing conversion time while maintaining accuracy through the use of pre-computed reference values
Solution Approach 2:
The patent replaces the mechanical/computational process of performing floating point mathematical calculations with a memory retrieval operation. Instead of executing complex trigonometric functions during conversion, the system substitutes this with table lookups using integer arithmetic and bit-shifting operations, which are computationally much simpler and faster to execute
2Productivity
If floating point unit (FPU) is used for conversion, then conversion speed improves, but device complexity and cost increase
Solution Approach 1:
The patent employs simpler, cheaper computational methods (integer arithmetic, bit-shifting, and table lookups) instead of expensive floating point hardware. This approach uses readily available processor instructions that are already present in most microprocessors, avoiding the need for additional FPU hardware while achieving sufficient conversion performance for the application
Solution Approach 2:
The patent introduces lookup tables as an intermediary data structure that mediates between the audio conversion requirements and the processor's computational capabilities. These tables serve as a bridge, allowing the system to achieve fast conversion speeds through memory access rather than requiring complex mathematical computation hardware
3Productivity
If lookup table with trigonometric function evaluations is used, then computational burden is reduced, but memory requirements increase
Solution Approach 1:
The patent segments the trigonometric function evaluation into discrete, pre-computed values stored in lookup tables. By dividing the continuous trigonometric function into discrete sample points that can be stored in memory, the system transforms a computationally intensive continuous operation into a series of simple discrete memory retrievals, improving conversion efficiency while managing memory usage through structured data organization
Data Source
AI summary
A system and method for converting a polyphonic note-based audio object to a Pulse Code Modulated (PCM) audio format is disclosed. An electronic communication device includes a memory containing a polyphonic note-based audio object containing at least two notes which overlap in at least some time interval and a lookup table containing trigonometric function evaluations. The polyphonic note-based audio object contains note frequency information. The polyphonic note-based audio object is converted to a PCM stream by generating PCM code words for each sample point in the PCM stream based upon the polyphonic note frequency information. The PCM code words are determined based upon selection of one or more of the trigonometric function evaluations within the look-up table. A speaker outputs audio based upon the PCM formatted stream.