Fricative Sound Frequency Exchange for Bandwidth Extension
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Solution Overview
Problem
Existing sound signal encoding methods, particularly bandwidth extension techniques, suffer from perceptual deterioration when encoding fricative sounds, especially under low-bit-rate conditions, as they fail to accurately represent high-frequency components, leading to distorted main frequency components in decoded sounds.
Innovation Solution
A decoding and encoding apparatus that adjusts frequency spectrum sequences by exchanging samples between low and high frequency bands based on whether a sound is identified as a hissing sound, using a fricative sound judgment mechanism to minimize perceptual deterioration, and incorporates bandwidth extension gain encoding to optimize bit allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bandwidth extension technique is used to compress sound signals by duplicating low-frequency samples for high frequencies, then compression efficiency is improved, but perceptual quality deteriorates for fricative sounds with high-frequency energy concentration
Solution Approach 1:
The patent changes the frequency domain parameters by detecting whether the sound is a fricative sound and then exchanging frequency samples between low and high frequency bands. For fricative sounds, high-frequency samples are moved to low-frequency positions and vice versa, allowing accurate representation of high-frequency energy concentration while maintaining compression efficiency through selective parameter transformation rather than simple duplication
Solution Approach 2:
The patent introduces dynamic adaptability by detecting sound type (fricative vs. non-fricative) and dynamically adjusting the frequency sample arrangement strategy. The system switches between different processing modes: bandwidth extension for normal sounds and frequency exchange for fricative sounds, making the compression algorithm adaptive to different sound characteristics rather than using a fixed approach
2Productivity
If bits are preferentially assigned to low-frequency samples in frequency spectrum encoding, then compression efficiency is improved, but accuracy of high-frequency components deteriorates
Solution Approach 1:
The patent applies inversion by exchanging the positions of low-frequency and high-frequency samples in the frequency spectrum for fricative sounds. Instead of assigning more bits to low frequencies as in conventional methods, the system inverts the frequency arrangement so that high-frequency samples (which contain the important energy information for fricative sounds) are placed in positions that receive preferential bit assignment, thereby achieving both compression efficiency and high-frequency accuracy
Data Source
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AI summary
A decoding apparatus includes: a bandwidth extending part 25 obtaining a decoded extended frequency spectrum sequence by arranging samples based on K samples included in a frequency-domain sample sequence obtained by decoding, on a higher side than the frequency-domain sample sequence; and a fricative sound adjustment releasing part 23 obtaining, if inputted information indicating whether a hissing sound or not indicates being a hissing sound, what is obtained by exchanging all or a part of a low-side frequency sample sequence existing on a lower side than a predetermined frequency in the decoded extended frequency spectrum sequence for all or a part of a high-side frequency sample sequence existing on a higher side than the predetermined frequency in the decoded extended frequency spectrum sequence as an adjusted 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.