Harmonic Transposer Using Adaptive Window Sizing
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Solution Overview
Problem
Existing harmonic transposition methods face challenges in achieving high frequency resolution for stationary sounds while maintaining good transient response, often requiring window switching which introduces signal artifacts and complexity.
Innovation Solution
The approach involves oversampling in the frequency domain based on the transposition factor, selecting appropriate analysis and synthesis windows, and ensuring time-alignment of transposed signals, without the need for window switching, to improve transient performance and reduce complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency resolution is used for transposition of stationary signals, then transposition quality is improved, but transient response deteriorates due to large window sizes
Solution Approach 1:
The patent applies dynamics by making the window size adaptive rather than fixed. The transposer automatically adjusts window length based on signal characteristics: using long windows for stationary portions to achieve high frequency resolution, and short windows for transient portions to maintain good temporal response. This dynamic adaptation eliminates the need for manual window switching while resolving the contradiction between frequency resolution and transient response.
Solution Approach 2:
The patent changes the parameter of window size dynamically based on signal analysis. By monitoring signal characteristics and adjusting the window length parameter accordingly, the system achieves high frequency resolution when needed while maintaining fast transient response when required, thus resolving the technical contradiction between these two opposing requirements.
2Reliability
If window switching is used to adapt to different signal characteristics, then transposition quality is improved, but device complexity increases due to transient detection and switching control
Solution Approach 1:
The patent implements self-service by enabling the transposer to automatically detect signal characteristics and adapt its own window size without external control. The system performs self-adjustment based on intrinsic signal properties, eliminating the need for complex external transient detection and window switching control mechanisms, thus reducing device complexity while maintaining high transposition quality.
3Speed
If window switching is implemented to handle transient and stationary portions, then transient response is improved, but signal artifacts are introduced during switching
Solution Approach 1:
The patent uses dynamic window size adaptation that transitions smoothly between different window lengths based on signal characteristics. This dynamic approach avoids abrupt window switching that causes artifacts, while still enabling the system to use short windows for transient portions to achieve good transient response without introducing harmful signal artifacts during transitions.
Data Source
AI summary
The present invention relates to transposing signals in time and/or frequency and in particular to coding of audio signals. More particular, the present invention relates to high frequency reconstruction (HFR) methods including a frequency domain harmonic transposer. A method and system for generating a transposed output signal from an input signal using a transposition factor T is described. The system comprises an analysis window of length La, extracting a frame of the input signal, and an analysis transformation unit of order M transforming the samples into M complex coefficients. M is a function of the transposition factor T. The system further comprises a nonlinear processing unit altering the phase of the complex coefficients by using the transposition factor T, a synthesis transformation unit of order M transforming the altered coefficients into M altered samples, and a synthesis window of length Ls, generating a frame of the output signal.