Audio Encoding Device Using Dual Search Sections for Low Bit Rate Quality
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Solution Overview
Problem
Scalable codecs face challenges in achieving sufficient perceptual performance at low bit rates, particularly in wideband applications where the number of available bits is limited, leading to inadequate encoding of spectral parameters using existing vector quantization methods.
Innovation Solution
A coding apparatus and method that separates shape and gain quantization in the frequency spectrum, employing interval and thorough search sections to accurately encode energy positions with a small number of pulses, ensuring good perceptual quality even at low bit rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vector quantization using codebooks is applied to encode spectrum at low bit rates, then the coding efficiency is improved, but the perceptual performance becomes insufficient
Solution Approach 1:
The invention segments the frequency spectrum into multiple bands and applies different coding strategies to each band. The interval search section handles broader frequency ranges with fewer pulses, while the thorough search section focuses on specific high-energy frequency positions. This segmentation allows efficient coding at low bit rates by concentrating resources where they are most needed, resolving the contradiction between coding efficiency and perceptual performance.
Solution Approach 2:
The invention applies different quantization precision locally across frequency bands. The thorough search section provides high precision coding for frequencies with high energy content, while the interval search section uses coarser quantization for lower energy regions. This local quality adjustment ensures that perceptually important frequencies receive accurate encoding, maintaining perceptual performance while optimizing overall coding efficiency at low bit rates.
2Quantity of substance
If the number of pulses used for encoding is reduced, then the bit rate is lowered, but the accuracy of frequency encoding deteriorates
Solution Approach 1:
The invention applies partial action by using the interval search section to handle the majority of frequency encoding with a small number of pulses, achieving sufficient accuracy for low-energy regions. The thorough search section provides excessive action (more precise encoding) only for high-energy frequency positions where it is most perceptually important. This partial/excessive action strategy maintains frequency encoding accuracy for critical frequencies while using fewer pulses overall, resolving the contradiction between quantity and precision.
3Device complexity
If conventional speech coding methods are used for wideband audio, then the device complexity is reduced, but the coding performance becomes insufficient
Solution Approach 1:
The invention creates a universal coding framework that can handle both speech and audio signals across different bandwidths. The dual-search mechanism (interval and thorough search sections) provides a multi-functional approach that works effectively for wideband audio while maintaining compatibility with speech coding requirements. This universality allows the system to achieve high coding performance for wideband audio without requiring entirely new complex methods, resolving the contradiction between device complexity and coding performance.
Data Source
AI summary
Provided is an encoding device which can obtain a sound quality preferable for auditory sense even if the number of information bits is small. The encoding device includes a shape quantization unit (111) having: a section search unit (121) which searches for a pulse for each of bands into which a predetermined search section is divided; and a whole search unit (122) which performs search for a pulse over the entire search section. The shape of an input spectrum is quantized by a small number of pulse positions and polarities. A gain quantization unit (112) calculates a gain of the pulse searched by the shape quantization unit (111) and quantizes the gain for each of the bands.