Audio Decoder Bandwidth Extension Energy Adjusting Module
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Solution Overview
Problem
Current SBR decoding techniques face challenges in maintaining audio quality during frame loss, particularly in bandwidth extension, where high band energies are not adequately adapted to low band energies, leading to perceptual degradation and artifacts.
Innovation Solution
The proposed audio decoder employs a gain locking mechanism, where high band energies are adjusted based on current and previous frame gain factors and signal energies, ensuring energy consistency between core and bandwidth extension modules, thereby avoiding uncontrolled fadeouts and artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high band energies are adjusted independently in current SBR decoding techniques, then bandwidth extension can be achieved, but energy consistency between core and bandwidth extension modules deteriorates, leading to perceptual degradation and artifacts
Solution Approach 1:
The patent combines the energy adjustment of high band and low band signals into a unified process controlled by a single gain factor. The energy adjusting module adjusts both high band and low band energies simultaneously based on the same gain factor derived from the bitstream, ensuring that energy consistency is maintained between core and bandwidth extension modules while achieving bandwidth extension.
2Reliability
If gain factors are adjusted during frame loss, then audio quality can be maintained, but uncontrolled fadeouts and artifacts may occur without proper energy coordination
Solution Approach 1:
The patent implements a feedback mechanism where the energy adjusting module continuously monitors and adjusts the energies of both high band and low band signals based on gain factors derived from the bitstream. During frame loss, this feedback-controlled energy adjustment ensures that energies remain coordinated, preventing uncontrolled fadeouts and artifacts while maintaining audio quality.
3Measurement precision
If separate energy adjustment is applied to high band and low band, then individual band optimization is possible, but perceptual degradation occurs due to energy mismatch
Solution Approach 1:
The patent changes the parameter control approach from independent energy adjustment to unified gain factor control. Instead of adjusting high band and low band energies separately, the system derives a single gain factor from the bitstream and applies it to both bands, ensuring energy consistency while maintaining the ability to optimize individual band energies through the coordinated adjustment mechanism.
Data Source
AI summary
An audio decoder configured to produce an audio signal from a bitstream containing audio frames includes: a core band decoding module configured to derive a directly decoded core band audio signal from the bitstream; a bandwidth extension module configured to derive a parametrically de-coded bandwidth extension audio signal from the core band audio signal and from the bitstream, wherein the bandwidth extension audio signal is based on a frequency domain signal having at least one frequency band; and a combiner configured to combine the core band audio signal and the bandwidth extension audio signal so as to produce the audio signal; wherein the bandwidth extension module includes an energy adjusting module being configured in such way that in a current audio frame in which an audio frame loss occurs, an adjusted signal energy for the cur-rent audio frame for the at least one frequency band is set.