Hierarchical Audio Coding Using MDCT Residual Envelope Allocation
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Solution Overview
Problem
Conventional hierarchical audio coding schemes suffer from low coding efficiency due to independent coding schemes for the core and extended layers, which do not consider the residual perception distribution characteristics of the audio signal, leading to suboptimal tone quality and bandwidth utilization.
Innovation Solution
A method that divides audio signal frequency domain coefficients into core and extended layers using Modified Discrete Cosine Transform (MDCT), allocates bits based on amplitude envelope values, and employs pyramid lattice vector quantization and sphere lattice vector quantization to improve bit allocation efficiency, while multiplexing and packing coded bits for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If independent coding schemes are used for core layer and extended layer, then the coding structure is simple and independent, but the coding efficiency is low and tone quality deteriorates
Solution Approach 1:
The patent merges the core layer and extended layer coding schemes into a unified framework. The extended layer uses the same MDCT-based transform coding as the core layer, rather than independent time-domain or transform-domain coding. This unified approach allows the extended layer to benefit from the core layer's frequency domain representation and bit allocation strategy, significantly improving overall coding efficiency while maintaining structural clarity.
Solution Approach 2:
The patent performs preliminary MDCT transformation and bit allocation for the core layer before encoding the extended layer. The core layer's frequency domain coefficients and amplitude envelope information are calculated first, and then the extended layer utilizes these pre-computed results to improve its own coding efficiency. This preliminary action allows the extended layer to start from a more advantageous position rather than beginning independently.
2Adaptability or versatility
If core layer and extended layer use different coding schemes, then each layer can be optimized independently, but the overall tone quality and bandwidth utilization are suboptimal
Solution Approach 1:
The patent makes the coding scheme universal by applying the same MDCT-based transform coding and bit allocation methodology to both core layer and extended layer. This universal approach ensures that both layers benefit from the same optimized frequency domain representation and perceptual weighting, achieving consistent high-quality results across different bit rates and conditions, rather than having separate specialized schemes that may not perform optimally in all scenarios.
3Device complexity
If bit allocation is performed without considering residual perception distribution characteristics, then the bit allocation process is simple, but the tone quality and bandwidth utilization are suboptimal
Solution Approach 1:
The patent implements feedback by using the core layer's amplitude envelope information and bit allocation results to guide the extended layer's bit allocation process. The extended layer considers the residual perception distribution characteristics that remain after core layer encoding, and adjusts its bit allocation accordingly. This feedback mechanism ensures that bits are allocated to the most perceptually important regions, maximizing tone quality and bandwidth utilization without excessive complexity.
Data Source
AI summary
A hierarchical audio coding, decoding method and system are provided. The method includes dividing frequency domain coefficients of an audio signal after MDCT into a plurality of coding sub-bands, quantizing and coding amplitude envelope values of coding sub-bands; allocating bits to each coding sub-band of the core layer, quantizing and coding core layer frequency domain coefficients to obtain coded bits of core layer frequency domain coefficients; calculating the amplitude envelope value of each coding sub-band of the core layer residual signal; allocating bits to each coding sub-band of the extended layer, quantizing and coding the extended layer coding signal to obtain coded bits of the extended layer coding signal; multiplexing and packing amplitude value envelope coded bits of each coding sub-band composed by core layer and extended layer frequency domain coefficients, core layer frequency coefficients coded bits, and extended layer coding signal coded bits, then transmitting to the decoding end.