Time-Varying Time-Frequency Tilings Using Non-Uniform Filterbanks
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Solution Overview
Problem
Time-domain aliasing reduction (TDAR) in audio processing is limited by the requirement for identical time-frequency tilings, which restricts flexibility and adaptability when dealing with changing signal characteristics, such as transients, as it needs to temporarily disable TDAR to switch between tilings.
Innovation Solution
Introducing a symmetric subband merging/subband splitting step to equalize time-frequency tilings of different frames, allowing TDAR to be applied between frames with varying tilings, and then reconstructing the original tilings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TDAR is used to obtain compact impulse responses and improved coding efficiency, then coding efficiency and perceptual quality are improved, but flexibility and adaptability are reduced because TDAR requires identical time-frequency tilings for adjacent frames
Solution Approach 1:
The patent introduces an intermediary time-frequency transform stage that acts as a mediator between frames with different tilings. This stage transforms subband samples from one tiling configuration to match another, enabling TDAR to operate on equalized tilings while the overall system maintains flexibility to handle varying signal characteristics. The intermediary transform allows TDAR to be applied without requiring identical original tilings.
Solution Approach 2:
The patent segments the processing into distinct stages: original transform stage, time-frequency transform stage for tiling equalization, and TDAR stage. By dividing the processing chain, the system can apply TDAR to specific segments (frames) that have been equalized, while other segments can maintain their original tiling configurations, thus maintaining overall system flexibility.
2Adaptability or versatility
If TDAR is applied between frames with different time-frequency tilings to enhance adaptability, then adaptability is improved, but the compact impulse response property is lost
Solution Approach 1:
The patent applies preliminary time-frequency transform to equalize the tilings of adjacent frames before applying TDAR. This preliminary action ensures that the conditions for obtaining compact impulse responses are met (identical tilings) while still allowing the system to adapt to different signal characteristics by choosing appropriate tiling configurations for different frames.
3Adaptability or versatility
If window switching is used to handle transients and changing signal characteristics, then adaptability is improved, but TDAR must be temporarily disabled resulting in loss of coding efficiency
Solution Approach 1:
The patent creates a universal processing framework that can handle both transient and non-transient signal characteristics while maintaining TDAR benefits. The system can adaptively choose different tiling configurations for different frames based on signal characteristics, and the time-frequency transform stage ensures TDAR can be applied regardless of tiling differences, making the system multi-functional in handling various signal types.
Data Source
AI summary
Embodiments provide a method for processing an audio signal, including: performing a cascaded lapped critically sampled transform on two partially overlapping blocks of samples of the audio signal, to obtain sets of subband samples; identifying one or more sets of subband samples that in combination represent the same region of the time-frequency plane; performing time-frequency transforms on the identified one or more sets of subband samples, to obtain one or more time-frequency transformed subband samples, each of which represents the same region in the time-frequency plane; performing a weighted combination of two corresponding sets of subband samples or time-frequency transformed versions thereof, to obtain aliasing reduced subband representations of the audio signal.