Music Signal Encoding Adjusting Spectrum Peak Amplitude
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Solution Overview
Problem
CELP encoding, effective for speech signals, significantly degrades sound quality when applied to music signals due to its inability to accurately express formant and harmonic structures present in music, leading to suppressed peak shapes and crests in the decoded signal spectrum, resulting in noise-like sound quality.
Innovation Solution
An encoding and decoding apparatus that calculates and adjusts the amplitude of peak components in the spectrum of music signals based on the fluctuation ratio between peak and floor components of the input and decoded signal spectra, using a characteristic parameter to enhance sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CELP encoding is applied to music signals, then encoding efficiency is improved, but sound quality deteriorates due to inability to express peak components
Solution Approach 1:
The patent segments the spectrum into peak components and floor components, applying different processing methods to each. Peak components are extracted and encoded separately with higher precision, while floor components use standard CELP encoding, thus resolving the contradiction between encoding efficiency and sound quality.
Solution Approach 2:
The patent applies different encoding qualities to different parts of the spectrum: high-quality encoding for peak components (which carry musical information) and standard encoding for floor components (which carry noise-like information), thereby improving overall sound quality without sacrificing encoding efficiency.
2Loss of substance
If standard CELP encoding is used, then bit rate is reduced, but peak shape collapse occurs in decoded music signals
Solution Approach 1:
The patent performs preliminary extraction and encoding of peak components before the main CELP encoding process. By identifying and preserving peak components in advance, the system prevents peak shape collapse in the decoded signal while maintaining low bit rate for the overall encoding.
Solution Approach 2:
The patent introduces an intermediary peak component extraction and encoding stage between the input signal and the CELP encoder. This intermediary process preserves peak information that would otherwise be lost in standard CELP encoding, preventing peak shape collapse while maintaining bit rate efficiency.
3Device complexity
If CELP encoding model is applied to music signals, then encoding complexity is reduced, but spectral accuracy deteriorates
Solution Approach 1:
The patent segments spectral processing into peak detection, peak component extraction, and floor component processing. This segmentation maintains relatively simple encoding complexity while significantly improving spectral accuracy by accurately representing peak components that define musical characteristics.
Solution Approach 2:
The patent changes the encoding parameters dynamically based on the detected peak components. By adjusting the encoding strategy according to the presence and characteristics of peak components, the system achieves high spectral accuracy without proportionally increasing encoding complexity.
Data Source
AI summary
An encoding device is provided for increasing the quality of an encoded signal, even when encoding music signals. In the encoding device, a Code-Excited Linear Prediction (CELP) encoder generates first encoded data by encoding an input signal, and a CELP decoder generates a decoded signal by decoding the first encoded data input from the CELP encoder. Additionally, a characteristic parameter encoder calculates a parameter that expresses the degree of fluctuation in the ratio of the peak components and the floor components between the spectra of the decoded signal and the input signal.