Stereo Signal Prediction Using Low-Pass Filtering
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Solution Overview
Problem
Existing stereo coding methods face challenges in reducing prediction errors and maintaining sound quality, as increasing the order of prediction coefficients to improve prediction performance leads to higher coding bit rates and degraded audio quality.
Innovation Solution
A stereo coding apparatus employing low pass filters to isolate low-band components of stereo signals, predicting one channel's low-band component from the other, and encoding these components to improve prediction performance while maintaining low prediction coefficient orders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the order of prediction coefficient is increased to reduce prediction errors, then prediction performance is improved, but coding bit rate increases
Solution Approach 1:
The patent divides the frequency spectrum into low-band and high-band components using low-pass filters. The prediction process is segmented to operate only on low-band components, separating the prediction function from the full-band signal processing. This segmentation allows accurate prediction with lower-order coefficients while excluding high-band components that would otherwise require higher prediction orders.
Solution Approach 2:
The patent extracts and removes high-band components from the prediction process by applying low-pass filters. Only the low-band components are subjected to inter-channel prediction, effectively taking out the problematic high-frequency elements that necessitate high prediction orders. This extraction maintains prediction accuracy for perceptually important low frequencies while reducing overall bit rate requirements.
2Quantity of substance
If the order of prediction coefficient is decreased to lower coding bit rate, then coding bit rate is reduced, but prediction performance deteriorates and sound quality degrades
Solution Approach 1:
The patent applies local quality by focusing prediction resources on the low-band frequency region where human auditory perception is most sensitive. Instead of attempting to predict all frequency components uniformly, the system concentrates prediction effort on low-band components using low-pass filtering. This localized approach ensures high prediction performance in the perceptually critical low-frequency range while using simpler (lower-order) prediction models overall, thus maintaining sound quality at lower bit rates.
3Quantity of substance
If low-pass filtering and inter-channel prediction on low-band components is applied, then prediction performance is improved and bit rate is reduced, but device complexity increases
Solution Approach 1:
The patent introduces dynamic adaptability by allowing the prediction system to adjust its operation based on signal characteristics. The low-pass filtering and inter-channel prediction are applied dynamically to extract and process only the necessary low-band components. This dynamic approach optimizes the balance between complexity and performance by activating sophisticated prediction only where needed (in low-band components) while keeping high-band processing simpler.
Data Source
AI summary
A prediction performance between individual channels of a stereo signal is improved to improve a sound quality of a decoded signal. A first low pass filter LPF interrupts a high-range component of a first channel signal S1, and outputs a first low-range component S1′. A second low pass filter LPF interrupts a high-range component of a second channel signal S2, and outputs a second low-range component S2′. A predictor predicts the S2′ from the S1′, and outputs a prediction parameter composed of a delay time difference t and an amplitude ratio g. first channel encoder encodes the S1. A prediction parameter encoder encodes the prediction parameter. The encoded parameters of the encoded parameter of the S1 and the prediction parameter are then outputted.