Audio Decoding Band Expansion Without Phase Distortion
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Solution Overview
Problem
Existing audio encoding and decoding technologies that perform band expansion in frequency regions suffer from sound quality degradation, especially with signals having energy concentrated at specific frequencies, due to disturbances in phase components and mutual phase relationships, and are resource-intensive, making them unsuitable for resource-poor settings.
Innovation Solution
A decoding device and method that acquire a low-band spectrum and a single expansion coefficient or coefficients for the expanded band, generating an expanded spectrum by adjusting the level of the low-band spectrum or bands, allowing for high-quality sound reproduction without the need for band dividing and combining processes, which reduces resource requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If band dividing filter and band combining filter are used for band expansion, then band expansion is achieved, but fundamental delay increases and response speed decreases
Solution Approach 1:
The patent extracts only the necessary information (amplitude spectrum and phase difference) from the original signal, avoiding the need for complex band dividing and combining filters. By taking out only the essential components needed for band expansion, the system achieves frequency region expansion without the fundamental delay and complexity associated with traditional filtering approaches.
Solution Approach 2:
The patent replaces the mechanical filtering system (band dividing filter and band combining filter) with a computational approach using amplitude spectrum analysis and phase difference calculation. This substitution eliminates the need for physical filter structures and their associated delays, achieving band expansion through mathematical operations instead of mechanical filtering.
2Quantity of substance
If band dividing filter and band combining filter are used for band expansion, then band expansion is achieved, but throughput and memory usage increase
Solution Approach 1:
The patent extracts only the essential information (amplitude spectrum and phase difference) from the original signal, avoiding the need for complex band dividing and combining filters. By taking out only the essential components needed for band expansion, the system achieves frequency region expansion without the fundamental delay and complexity associated with traditional filtering approaches.
Solution Approach 2:
The patent uses simple computational operations (amplitude spectrum calculation and phase difference measurement) instead of expensive, resource-intensive filter banks. These lightweight computational elements consume minimal memory and processing power, making the system suitable for resource-poor embedded devices while achieving the same band expansion function.
3Manufacturing precision
If amplitude of expanded band spectrum is minutely adjusted using MDCT spectrum, then band expansion is achieved, but phase component and mutual phase relationship are disturbed
Solution Approach 1:
The patent introduces phase difference as an intermediary parameter that mediates between the amplitude spectrum adjustment and the phase information preservation. By calculating and preserving the phase difference between the original and expanded bands, the system can adjust amplitude while maintaining phase relationships, thus preserving sound quality without distorting phase components.
Solution Approach 2:
The patent changes the approach from directly adjusting MDCT spectrum values (which disturbs phase) to adjusting amplitude spectrum based on calculated amplitude ratios while separately preserving phase difference information. This parameter change separates amplitude control from phase control, allowing precise amplitude adjustment without phase distortion.
Data Source
AI summary
The present technology relates to an encoding device and a method, a decoding device and a method, and a program that enables acquisitions of high-quality sound even in a resource-poor setting.A demultiplexer demultiplexes a supplied code string, to obtain the quantized low-band spectrum, the spectral characteristic code, and the quantized expansion coefficient(s). At this point, the code string includes a single quantized expansion coefficient or quantized expansion coefficients of the respective bands in the high band depending on the spectral characteristic code. A spectral inverse quantization unit obtains the low-band spectrum by inversely quantizing the quantized low-band spectrum. An expansion coefficient inverse quantization unit obtains the expansion coefficient(s) by inversely quantizing the quantized expansion coefficient(s). An expanded spectrum generation unit generates an expanded spectrum, in accordance with the low-band spectrum and the expansion coefficient(s) depending on the spectral characteristic code. An IMDCT unit generates a band-expanded time-series signal from the low-band spectrum and the expanded spectrum. The present technology can be applied to decoding devices.