Plural Lookup Table Audio Encoding for Adaptive Bit Allocation
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Solution Overview
Problem
Conventional digital signal encoding methods using psychoacoustic models require complex computations and result in significant real-time delays due to the need for calculating signal-to-mask ratios, which limits their efficiency in adaptive bit allocation for digital audio transmission.
Innovation Solution
A digital signal encoding method and apparatus utilizing multiple lookup tables, where each table is generated based on the characteristics of input signals, allowing for adaptive bit allocation per frequency band, reducing computational complexity and real-time delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a psychoacoustic model is used to calculate signal-to-mask ratios for bit allocation, then bit allocation accuracy is improved, but computational complexity increases and real-time delay increases
Solution Approach 1:
The patent pre-calculates and stores bit allocation values in lookup tables during an offline phase, so that during real-time encoding, only table lookup is required. This preliminary preparation eliminates the need for complex real-time psychoacoustic calculations while maintaining allocation accuracy.
Solution Approach 2:
The patent creates simplified copies of the complex psychoacoustic model by storing pre-computed results in lookup tables. These tables represent the complex calculations in a simplified form that can be quickly accessed during encoding without repeating the full psychoacoustic analysis.
2Measurement precision
If a psychoacoustic model is used to calculate signal-to-mask ratios for bit allocation, then bit allocation accuracy is improved, but real-time delay increases
Solution Approach 1:
The patent performs the time-consuming psychoacoustic calculations and bit allocation decisions in advance, storing results in lookup tables. During real-time encoding, the system only needs to perform quick table lookups based on signal characteristics, dramatically reducing processing delay while maintaining allocation accuracy.
Solution Approach 2:
The patent creates a simplified representation of the complex bit allocation process by storing pre-computed allocation values in lookup tables. This copy allows rapid access during encoding without repeating the full psychoacoustic analysis, thus reducing real-time delay.
3Device complexity
If a single lookup table is used for bit allocation, then computational complexity is reduced, but adaptability to different signal characteristics deteriorates
Solution Approach 1:
The patent divides a single lookup table into multiple lookup tables, each specialized for different signal characteristics (e.g., different occupancy rates). The system selects the appropriate table based on the input signal's characteristics, providing adaptability while keeping each individual table simple for fast lookup.
Solution Approach 2:
The patent creates lookup tables with different structures and allocations tailored to specific signal types or characteristics. Each lookup table is optimized for its intended signal category, allowing the system to adapt to different input signals by selecting the matching table, thus providing local optimization for different signal conditions.
Data Source
AI summary
A digital signal encoding method and apparatus using a plurality of lookup tables. The method includes: preparing a plurality of lookup tables storing numbers of allocated bits for encoding frequency bands of an input signal according to a characteristic of the input signal in a predetermined number of addresses; dividing an input signal in the time domain into signals in predetermined frequency bands; calculating address values of the frequency bands; selecting one of the plurality of lookup tables according to the characteristic of the input signal; extracting numbers of allocated bits of addresses having the calculated address values from the selected lookup table with respect to the frequency bands and allocating the numbers of bits to the frequency bands; and generating a bitstream by quantizing the input signal according to the numbers of allocated bits. Bit amount control suitable for a characteristic of an input signal can be performed by extracting numbers of allocated bits of frequency bands from an optimal lookup table selected according to the characteristic of the input signal. Also, an additional computational time can be reduced by using each occupancy rate per frequency band equal to each address of the lookup table as the characteristic of the input signal.