Audio Encoding Device Space Information Smoothing
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Solution Overview
Problem
Existing audio encoding methods, such as HE-AAC ver.2, face challenges in reducing the data amount of stereo signals while maintaining sound quality, particularly in frequency bands not important for human hearing, which affects the bit rate allocation to other audio codes.
Innovation Solution
An audio encoding device that includes time-frequency transform units, a down-mix unit, low channel encoding units, space information extraction and correction units, and multiplexing, which transforms stereo signals into frequency signals, down-mixes them, extracts and corrects space information based on importance, and encodes the differences to reduce data amount by smoothing unimportant frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If space information is encoded for all frequency bands, then sound quality is maintained, but data amount increases
Solution Approach 1:
The patent applies local quality by differentiating the encoding precision of space information across different frequency bands. Important frequency bands (where human hearing is sensitive) are encoded with high precision to maintain sound quality, while unimportant frequency bands are encoded with low precision or smoothed to reduce data amount. This selective approach resolves the contradiction between maintaining sound quality and reducing data size.
Solution Approach 2:
The patent changes the parameter of encoding precision for space information based on frequency band importance. By dynamically adjusting the quantization precision and smoothing degree according to perceptual importance, the system optimizes the balance between sound quality and compression efficiency, reducing data amount in unimportant bands while preserving quality in important bands.
2Measurement precision
If more bits are allocated to space information encoding, then spatial accuracy is improved, but bits available for audio coding decrease
Solution Approach 1:
The patent allocates encoding bits non-uniformly across frequency bands based on perceptual importance. High-importance bands receive more bits for accurate space information encoding to maintain spatial accuracy, while low-importance bands receive fewer bits or are smoothed. This local differentiation ensures spatial accuracy where needed while conserving bits for audio coding overall.
Solution Approach 2:
The system dynamically changes the encoding parameter (quantization precision) of space information based on the calculated perceptual importance of each frequency band. This adaptive parameter adjustment optimizes bit allocation, ensuring spatial accuracy in critical bands while minimizing bit consumption in non-critical bands, thereby preserving bits for audio coding.
3Quantity of substance
If space information is smoothed in frequency direction, then data amount is reduced, but spatial resolution deteriorates
Solution Approach 1:
The patent applies smoothing selectively only to unimportant frequency bands where human hearing is less sensitive. Important frequency bands maintain their original space information without smoothing, preserving spatial resolution where it matters most. This localized smoothing approach reduces data amount in unimportant bands while maintaining spatial resolution in important bands.
Solution Approach 2:
The smoothing degree and application range of space information are dynamically adjusted based on perceptual importance. In unimportant bands, aggressive smoothing is applied to reduce data amount; in important bands, minimal or no smoothing is applied to preserve spatial resolution. This adaptive parameter control resolves the contradiction between compression and quality.
Data Source
AI summary
An audio encoding device includes, a time-frequency transform unit that transforms signals of channels included in an audio signal having a first number of channels into frequency signals respectively, a down-mix unit that generates an audio frequency signal having a second number of channels, a low channel encoding unit that generates a low channel audio code by encoding the audio frequency signal, a space information extraction unit that extracts space information representing spatial information of a sound, an importance calculation unit that calculates importance on the basis of the space information, a space information correction unit that corrects the space information, a space information encoding unit that generates a space information code, and a multiplexing unit that generates an encoded audio signal by multiplexing the low channel audio code and the space information code.