Adaptive Extended TDAC Filter Bank for Transient Audio Coding
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Solution Overview
Problem
Existing perceptual audio coding systems face challenges in efficiently adapting to varying audio signal characteristics, particularly in balancing frequency and time resolution, especially during transient conditions, due to the limitations of traditional TDAC transforms.
Innovation Solution
Implementing an adaptive extended time-domain aliasing cancellation (TDAC) filter bank using a discrete trigonometric transform preceded by a folding matrix, allowing for dynamic adjustment of window lengths and hop sizes based on input signal characteristics, and employing block switching methods to transition between different TDAC transforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If extended TDAC transforms with longer analysis windows are used, then frequency resolution is improved, but time resolution deteriorates
Solution Approach 1:
The patent implements a dynamic block switching mechanism that adapts the TDAC transform block size based on signal characteristics. During steady-state conditions, larger blocks are used to achieve high frequency resolution. During transient conditions, the system switches to smaller blocks to maintain time resolution. This dynamic adaptation resolves the contradiction by making the system flexible rather than fixed.
Solution Approach 2:
The system changes the parameter of block size dynamically based on signal analysis. By monitoring signal characteristics and adjusting the TDAC block length accordingly, the system optimizes frequency resolution when signals are stable and time resolution when transients occur, effectively managing the trade-off between these two parameters.
2Productivity
If high-frequency resolution filter banks are used, then redundancy removal efficiency is improved, but adaptability to transient signals deteriorates
Solution Approach 1:
The filter bank system dynamically adjusts its configuration based on signal type. For steady-state signals, it operates in high-frequency resolution mode for efficient redundancy removal. For transient signals, it switches to smaller blocks that provide better time resolution, thus adapting to different signal characteristics and maintaining versatility.
Solution Approach 2:
The TDAC filter bank is designed to perform multiple functions by switching between different block sizes. It can handle both steady-state signals with high frequency resolution and transient signals with better time resolution, making it a universal solution that adapts to various audio signal types rather than being specialized for one condition.
3Ease of manufacture
If fixed block size TDAC transforms are used, then implementation simplicity is maintained, but adaptability to varying signal characteristics deteriorates
Solution Approach 1:
The system transitions from a fixed block size approach to a dynamic block switching approach. The implementation includes a signal analysis component that determines optimal block sizes and a switching mechanism that adapts the transform parameters accordingly. This maintains relative implementation simplicity while dramatically improving adaptability to varying signal characteristics.
Solution Approach 2:
The audio signal is processed in variable-sized blocks rather than fixed blocks. The system segments the signal adaptively, using larger segments for steady-state portions and smaller segments for transient portions. This segmentation strategy maintains implementation feasibility while enabling adaptation to different signal characteristics.
Data Source
AI summary
Audio processing systems are described that include filter banks capable of performing adaptive extended time-domain aliasing cancellation (TDAC) transforms for efficient audio encoding and decoding. In many instances, the system includes an audio encoder with a time domain to frequency domain mapping filter bank that performs an adaptive extended TDAC transform, which is implemented as a discrete trigonometric transform (DTT) preceded by a folding matrix. A corresponding audio decoder inverts this transform using the transpose of the DTT and folding matrix. This approach enables improved frequency responses with dynamic adjustment of time-frequency resolution based on input signal characteristics, improving coding efficiency.