Fricative Sound Encoding With Adaptive High-Frequency Bit Allocation
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Solution Overview
Problem
Conventional sound signal encoding methods, such as those described in Non-patent Literature 1, often result in perceptual deterioration of fricative sounds, especially under low-bit-rate conditions, due to inadequate bit allocation, leading to distortion of the main frequency component in sounds with high energy concentrated at high frequencies.
Innovation Solution
An encoding and decoding apparatus that includes a fricative sound judging part and a fricative sound adjusting part to dynamically adjust the bit allocation between low-side and high-side frequency spectrum sequences, ensuring that the number of bits on both sides is equalized, thereby reducing perceptual deterioration without altering the encoding apparatus configuration significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If bits are preferentially assigned to low frequencies in the frequency spectrum sequence, then compression efficiency is improved and low frequency information is accurately expressed, but high frequency information is lost or distorted
Solution Approach 1:
The patent applies dynamics by making the bit allocation strategy adaptive rather than fixed. The encoding apparatus dynamically switches between two bit allocation modes (low-frequency priority and high-frequency priority) based on the detected sound type. This allows the system to optimize bit distribution in real-time according to the characteristics of the input sound signal, resolving the contradiction between compression efficiency and high frequency information preservation.
Solution Approach 2:
The patent changes the parameter of bit allocation strategy based on sound type detection. By detecting whether the sound is speech or non-speech (including fricative sounds), the system adjusts the bit allocation parameters accordingly. For non-speech sounds with high frequency energy concentration, the system switches to high-frequency priority allocation, thereby preserving high frequency information while maintaining acceptable compression efficiency.
2Productivity
If bits are not assigned to high frequency samples, then compression ratio is increased, but decoded sound quality for fricative sounds is deteriorated
Solution Approach 1:
The system dynamically adjusts bit allocation based on sound type detection. For fricative sounds detected as non-speech, the system switches to high-frequency priority bit allocation, ensuring that high frequency samples receive sufficient bits to maintain sound quality. This dynamic adaptation allows the system to maintain high compression ratios for speech while preserving sound quality for non-speech sounds.
Solution Approach 2:
The patent applies local quality by differentiating bit allocation strategies for different frequency regions based on sound type. For non-speech sounds, the system prioritizes high frequency regions with local quality enhancement, while for speech, it prioritizes low frequency regions. This localized optimization ensures that bits are allocated to the most perceptually important frequency regions for each sound type.
3Adaptability or versatility
If a fixed bit allocation strategy is used, then encoding complexity is reduced, but adaptability to different sound types is insufficient
Solution Approach 1:
The patent segments the encoding process into distinct stages: sound type detection, conditional judgment, and selective bit allocation. By dividing the encoding process into these segments, the system adds adaptability through sound type classification while keeping each segment's complexity manageable. The segmentation allows the system to apply different simplified strategies for speech and non-speech sounds.
Solution Approach 2:
The system performs preliminary action by detecting the sound type before bit allocation. This preliminary detection step allows the system to pre-determine the appropriate bit allocation strategy, avoiding complex real-time adjustments during encoding. The preliminary classification simplifies the overall encoding complexity while maintaining high adaptability to different sound types.
Data Source
AI summary
An encoding apparatus performing encoding by an encoding process in which bits are preferentially assigned to a low side to obtain a spectrum code, the encoding apparatus judging whether a sound signal is a hissing sound or not, obtaining and encoding, if the encoding apparatus judges that the sound signal is a hissing sound, what is obtained by exchanging all or a part of a spectrum existing on a lower side than a predetermined frequency in a frequency spectrum sequence of the sound signal for all or a part of a spectrum existing on a higher side of the predetermined frequency in the frequency spectrum sequence, the number of all or the part of the high-side frequency spectrum sequence being the same as the number of all or the part of the low-side frequency spectrum sequence.