Vector Quantization Pulse Polarity Pre-selection
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Solution Overview
Problem
Current speech coding technologies face challenges in reducing calculation complexity without degrading sound quality, particularly due to erroneous pulse polarity selection in fixed codebook searches, which affects the efficiency of speech codecs like ITU-T standard G.729.
Innovation Solution
A vector quantization apparatus and method that calculates reference vectors using speech spectrum characteristics and high-pass filters, and selects pulse polarities based on the polarity of elements in the second reference vector to minimize coding distortion and reduce calculation complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pre-selection of fixed codebook pulse polarity is employed to reduce calculation complexity, then the amount of calculation is significantly reduced, but erroneous polarity selection occurs leading to degradation of sound quality
Solution Approach 1:
The patent applies preliminary action by pre-selecting pulse polarities based on the sign of correlation values between code vectors and speech signals before the full search process. This preliminary selection reduces the search space and calculation complexity while maintaining accuracy by ensuring that pre-selected polarities match the actual optimal polarities in most cases, thereby avoiding erroneous selections that would degrade sound quality
Solution Approach 2:
The patent employs parameter changes by introducing a correlation value parameter (positive or negative) to guide the pre-selection of pulse polarities. By changing the selection criterion from random or fixed polarity assignment to polarity assignment based on correlation sign, the system maintains high accuracy in polarity selection while still reducing calculation complexity through pre-selection
2Reliability
If full search of pulse positions and polarities is performed to maintain sound quality, then optimal pulse polarity is selected, but the amount of calculation increases significantly
Solution Approach 1:
The patent applies segmentation by dividing the pulse selection process into two stages: pre-selection stage where polarities are determined based on correlation signs, and final search stage where only position optimization is performed. This segmentation separates the polarity determination (which has high impact on quality) from position optimization, reducing overall calculation complexity while maintaining sound quality
Solution Approach 2:
The patent performs preliminary action by determining pulse polarities in advance based on correlation analysis before the exhaustive search. This preliminary determination of polarities eliminates the need to search all polarity combinations during the final optimization stage, significantly reducing calculation complexity while ensuring optimal polarities are selected for maintaining sound quality
Data Source
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AI summary
Provided are a vector quantization device, a voice coding device, a vector quantization method, and a voice coding method which enable a reduction in the calculation amount of voice codec without deterioration of voice quality. In the vector quantization device, a first reference vector calculation unit (201) calculates a first reference vector by multiplying a target vector (x) by an auditory weighting LPC synthesis filter (H), and a second reference vector calculation unit (202) calculates a second reference vector by multiplying an element of the first reference vector by a filter having a high pass characteristic. A polarity preliminary selection unit (205) generates a polar vector by disposing a unit pulse having a positive or negative polarity, which is selected on the basis of the polarity of an element of the second reference vector, in the position of said element.