Padded Audio Block Phase Processing for Transient Aliasing
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Solution Overview
Problem
Existing bandwidth extension algorithms in audio codecs suffer from quality degradation due to temporal aliasing and dispersion of waveforms caused by phase modifications in phase vocoders, particularly affecting transients, while maintaining computational efficiency is a challenge.
Innovation Solution
Generate padded blocks of audio samples with added values before modifying phases in the spectral representation, and convert these blocks into a modified time domain signal, removing the padding after phase modification to prevent temporal aliasing and maintain audio quality with reduced computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase modification is applied in bandwidth extension algorithms, then spectral representation is achieved, but temporal aliasing and waveform dispersion occur causing quality degradation
Solution Approach 1:
The audio signal is divided into multiple blocks, with certain blocks identified as containing transients. Different processing strategies are applied to different block types: padded blocks for transient-containing segments and non-padded blocks for regular segments, allowing selective handling of problematic cases while maintaining efficiency for common cases
Solution Approach 2:
Padded blocks are created in advance by inserting zero-valued padding samples at the beginning and/or end of blocks containing transients before phase modification. This preliminary action prepares the blocks to avoid temporal aliasing and waveform dispersion during subsequent phase vocoder processing
2Manufacturing precision
If padded blocks are generated and processed to prevent temporal aliasing, then audio quality is maintained, but computational complexity increases
Solution Approach 1:
Instead of applying padded block processing to all blocks uniformly, the invention identifies specific blocks containing transients and applies padding only to those local regions. This selective approach maintains audio quality where needed while avoiding unnecessary computational overhead in regular blocks
Solution Approach 2:
The invention changes the block structure parameter (adding padding) selectively based on the content characteristics (presence of transients). By modifying the block parameters only when necessary, the system achieves quality improvement without proportional increase in overall computational complexity
Data Source
AI summary
A device and method for manipulating an audio signal includes a windower for generating a plurality of consecutive blocks of audio samples, the plurality of consecutive blocks including at least one padded block of audio samples, the padded block having padded values and audio signal values. a first converter for converting the padded block into a spectral representation having spectral values, a phase modifier for modifying phases of the spectral values to obtain a modified spectral representation and a second converter for converting the modified spectral representation into a modified time domain audio signal.