Transform Coding Windows Adapted by Irregular Sampling
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Solution Overview
Problem
Existing audio signal processing technologies require significant memory storage for multiple analysis and synthesis windows of different sizes to maintain perfect reconstruction conditions, leading to increased memory usage and computational overhead, especially when adapting to varying frame sizes or sampling frequencies.
Innovation Solution
The method involves irregular sampling of an initial window to apply a secondary transform of a different size without preliminary computations, allowing a single window to adapt to various sizes while maintaining perfect or quasi-perfect reconstruction conditions through decimation or interpolation, thereby reducing memory requirements and computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple analysis and synthesis windows of different sizes are stored in memory to maintain perfect reconstruction conditions, then the reconstruction quality is improved, but the memory usage increases
Solution Approach 1:
A single analysis window of size N is designed to serve multiple transform sizes (N, N/2, N/4, etc.) through irregular sampling. The window coefficients are selectively sampled at different rates to generate appropriate windows for various transform sizes, eliminating the need to store separate windows for each size while maintaining perfect reconstruction conditions.
Solution Approach 2:
The invention changes the sampling parameters (sampling rate and pattern) of a single window to adapt it to different transform sizes. By varying the sampling density and pattern, the same base window can be transformed into windows of different effective sizes suitable for different transform operations, thereby reducing memory requirements.
2Adaptability or versatility
If multiple analysis and synthesis windows of different sizes are stored in memory, then the adaptability to varying frame sizes is improved, but the device complexity increases
Solution Approach 1:
The single window structure is designed to be universal across multiple transform sizes and frame configurations. Through irregular sampling with different rates and patterns, the same window serves multiple purposes for different frame sizes and sampling frequencies, reducing device complexity while maintaining high adaptability.
Solution Approach 2:
The window sampling process is made dynamic by allowing the sampling rate and pattern to be adjusted based on the required transform size. This dynamic adaptation enables the system to handle varying frame sizes efficiently without requiring pre-stored windows for each possible configuration, thereby reducing device complexity.
3Reliability
If preliminary computations are performed to adapt windows to different sizes, then the reconstruction quality is improved, but the computational overhead increases
Solution Approach 1:
The base window of size N is computed in advance and stored, serving as a foundation for all smaller transform sizes. This preliminary computation eliminates the need to compute multiple windows from scratch, as the pre-computed base window can be irregularly sampled to generate windows for N/2, N/4, and other smaller sizes, thereby reducing computational overhead while maintaining reconstruction quality.
Data Source
AI summary
A method and device are provided for coding or decoding a digital audio signal by transform using analysis or synthesis weighting windows applied to sample frames. The method includes an irregular sampling of an initial window provided for a transform of given initial size N, to apply a secondary transform of size M different from N.