Audio Signal Phase Modification With Padded Transient Blocks
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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, convert them to spectral representations, modify phases, and then convert back to the time domain, removing padding to prevent cyclic convolution and maintain audio quality with reduced computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phase modification is applied in bandwidth extension algorithms, then high-frequency content is generated from low-frequency parts, but temporal aliasing and waveform dispersion occur degrading audio quality
Solution Approach 1:
The audio signal is divided into multiple blocks, with transient-containing blocks identified and processed separately using padded values. This segmentation allows standard phase modification for normal blocks while applying protective padding only where needed, preventing temporal aliasing in transient regions without sacrificing bandwidth extension quality.
Solution Approach 2:
Padded values are inserted into blocks containing transients before phase modification is applied. This preliminary action creates a buffer that prevents waveform dispersion and temporal aliasing during the phase modification process, thereby preserving audio quality while still enabling bandwidth extension.
2Manufacturing precision
If padded blocks are generated for transient handling, then temporal aliasing is prevented, but computational complexity increases
Solution Approach 1:
Padded values are inserted only into specific blocks that contain transients, rather than uniformly processing all blocks. This localized approach maintains high audio quality where needed while minimizing computational overhead in normal blocks, effectively resolving the contradiction between precision and complexity.
Solution Approach 2:
The system dynamically changes processing parameters by detecting transient content in each block and conditionally applying padding. This parameter change strategy enables adaptive computational complexity, using padded blocks only when necessary for quality preservation rather than always.
3Productivity
If standard phase vocoder is used for bandwidth extension, then processing efficiency is maintained, but vertical coherence over sub-bands is not preserved
Solution Approach 1:
Padded values are inserted before phase modification to preserve vertical coherence in transient blocks, while standard phase vocoder processing maintains efficiency in non-transient blocks. This preliminary protective action resolves the coherence issue without sacrificing overall processing efficiency.
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.