Common Signal Extraction for Natural Stereo-to-Surround Audio
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Solution Overview
Problem
Conventional upmixing methods for stereo audio to surround sound configurations often produce unnatural-sounding artifacts, leading to a diminished listening experience due to the addition of fake or hollow effects, and peak limiters compromise clarity and punch with unwanted spectral artifacts.
Innovation Solution
An audio signal processing technique that extracts a common signal from stereophonic audio to convert it into surround sound without adding artificial cues, isolating and placing audio segments into their appropriate locations in the sound field, and a peak limiter cleanser that removes undesirable spectral information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional upmixing methods are used to convert stereo to surround sound, then additional audio channels are generated, but unnatural-sounding artifacts are produced
Solution Approach 1:
The patent extracts the common signal component from the stereo left and right channels by computing their sum, separating it from the differential information. This extracted common signal is then used to generate the center channel and rear channels, avoiding the need to synthesize artificial surround effects and thereby eliminating unnatural artifacts while maintaining authentic spatial positioning.
Solution Approach 2:
The patent segments the stereo signal into distinct components: the common signal (sum of L and R) and the differential signal (difference between L and R). By processing these segments separately and assigning them to different spatial positions, the system creates a natural surround sound field without mixing artificial effects, thus resolving the contradiction between surround capability and artifact-free sound quality.
2Reliability
If conventional peak limiters are applied to control audio peaks, then peak levels are limited effectively, but clarity and punch are lost with added spectral artifacts
Solution Approach 1:
The patent applies peak limiting only to the extracted common signal component rather than the entire mixed signal. By isolating and limiting the common signal separately, the system maintains effective peak control while preserving the clarity and punch of the differential signal components, thereby avoiding the spectral artifacts that would result from limiting the complete signal mixture.
3Adaptability or versatility
If matrixing, phasing, time delay, and reverberation effects are added to generate surround sound, then additional channels are created, but the sound becomes fake and hollow
Solution Approach 1:
Instead of adding artificial effects like matrixing, phasing, time delay, and reverberation, the patent extracts the genuine common signal information already present in the stereo mix and uses it directly to populate the center and rear channels. This extraction approach creates surround channels from authentic spatial information, eliminating the need for fake or hollow artificial effects while maintaining natural sound quality.
Data Source
AI summary
Extracting a common signal from multiple audio signals may include summing a first signal and a second signal to obtain a first+second signal; subtracting the second signal from the first signal to obtain a first−second signal; transforming the first+second signal and the first−second signal to frequency domain representations; calculating absolute value of the frequency domain representations of the first+second signal and the first−second signal; subtracting the absolute value of the frequency domain representation of the first−second signal from the absolute value of the frequency domain representation of the first+second signal to obtain a difference signal; multiplying the difference signal by the frequency domain representation of the first+second signal to obtain a product signal; dividing the product signal by the absolute value of the frequency domain representation of the first+second signal to obtain a frequency domain representation of the common signal; and transforming the frequency domain representation to the common signal.