Warped Spectral Audio Equalization for Real-Time Loudness Control
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Solution Overview
Problem
Existing audio processing technologies fail to consistently adjust loudness and spectral content of digital audio signals to suit varying user environments and hardware, leading to unsatisfactory playback experiences, especially in noisy conditions or with poor headphones.
Innovation Solution
A warped spectral processing module that uses a warped delay line and filter block to adjust digital audio signals in real-time, defining non-linearly-scaled frequency bands and applying dynamic range control and equalization, allowing independent gain settings for each band and embedding the module between quadrature mirror filter blocks for efficient processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional linear frequency scaling is used in audio equalization, then the spectral content can be modified, but the processing becomes computationally expensive and produces phasing artifacts at high sample rates
Solution Approach 1:
The patent applies frequency warping by transforming the linear frequency scale to a non-linear scale using a warping factor. This parameter change in the frequency domain allows the system to achieve accurate spectral modification while reducing computational complexity and eliminating phasing artifacts that occur with conventional linear scaling methods at high sample rates
Solution Approach 2:
The patent introduces a variable warping factor that can be adjusted dynamically based on the sample rate and desired frequency resolution. This dynamic parameter allows the system to adapt the frequency scaling behavior in real-time, optimizing the balance between spectral accuracy and computational efficiency for different operating conditions
2Illumination intensity
If aggressive amplification is applied to quiet audio signals, then loudness is improved, but distortion and noise are amplified along with the signal
Solution Approach 1:
The patent applies different processing characteristics to different frequency bands through the warped frequency scaling. By dividing the spectrum into bands with non-linear spacing, the system can apply targeted amplification to quiet signals in specific frequency ranges while maintaining better control over distortion and noise in other bands, rather than uniform aggressive amplification across the entire spectrum
3Manufacturing precision
If high sample rates are used for audio processing, then audio quality is improved, but computational resources and processing time increase significantly
Solution Approach 1:
The frequency warping transformation changes the parameter of frequency scaling from linear to non-linear, which allows the system to achieve high-quality spectral processing at reduced sample rates. The warping factor effectively compresses the frequency spectrum in a way that maintains audio quality while enabling lower computational requirements
Data Source
AI summary
This invention describes a method for adjusting the loudness and the spectral content of digital audio signals in a real-time using warped spectral filtering. A warped processing module modifies a spectral content of a digital audio signal with a set of gains for a plurality of non-linearly-scaled frequency bands determined by a warping factor λ of a warped delay line. Warped delay line signals, generated by the warped delay line, are processed by a warped filter block containing multiple warped finite impulse response filters, e.g., Mth band filters, using individual warped spectral filtering in said plurality of the non-linearly-scaled frequency bands, which is followed by a conventional processing by a dynamic range control/equalization block. The present invention describes another innovation, that is embedding the warped processing module in a two-channel quadrature mirror filter (QMF) bank for improving processing efficiency at high sample rates.