Adaptive Diffuse Signal Generation in Audio Upmixers
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Solution Overview
Problem
Existing audio upmixing technologies struggle to effectively process diffuse and directional audio signals, often resulting in a lack of punch in transient audio moments and an artificial sound field due to uniform distribution of diffuse signals across channels, which affects the perception of spatial sound.
Innovation Solution
The method involves detecting transient and non-transient audio signal conditions to dynamically adjust the distribution of diffuse audio signals, concentrating them near input channels during transients and distributing uniformly during non-transients, using a variable mixing matrix derived from transient and non-transient matrices, and applying psychoacoustic decorrelation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diffuse audio signals are distributed uniformly across all output channels, then the envelopment of the diffuse sound field is improved, but the impact of transient audio signals deteriorates
Solution Approach 1:
The patent applies dynamics by making the distribution matrix time-varying and adaptive. The system dynamically adjusts the distribution of diffuse audio signals based on detected transient conditions. During transient events, the matrix concentrates signals to specific channels to maintain impact, while during non-transient periods, it distributes signals uniformly to maximize envelopment. This temporal adaptability resolves the contradiction between maintaining transient impact and providing diffuse envelopment.
Solution Approach 2:
The system changes the parameter of signal distribution by using different distribution matrices for transient and non-transient conditions. The transient distribution matrix concentrates diffuse signals to channels closer to the apparent sound location, while the non-transient matrix distributes signals uniformly across all channels. This parameter switching allows the system to optimize for either transient impact or diffuse envelopment depending on the audio content.
2Object-generated harmful factors
If diffuse audio signals are concentrated near input channels during transients, then the impact of transient audio is improved, but the envelopment of the diffuse sound field deteriorates
Solution Approach 1:
The system dynamically switches between concentrated and uniform distribution strategies based on transient detection. The distribution matrix is adapted in real-time to concentrate signals during transients for maximum impact, then transitions to uniform distribution during non-transient periods to restore envelopment. This dynamic behavior allows the system to temporarily prioritize transient impact without permanently sacrificing diffuse envelopment.
Solution Approach 2:
The system applies periodic action by alternating between concentrated distribution (during transient periods) and uniform distribution (during non-transient periods). The transient detection mechanism triggers concentrated distribution only when needed, allowing the system to periodically switch strategies based on the temporal characteristics of the audio signal, thus maintaining both transient impact and overall envelopment.
3Device complexity
If a fixed distribution matrix is used for diffuse audio signals, then the device complexity is reduced, but the adaptability to different audio signal conditions deteriorates
Solution Approach 1:
The patent implements dynamics by replacing a fixed distribution matrix with a time-varying adaptive matrix. The system detects transient conditions and automatically selects appropriate distribution matrices (transient or non-transient) based on the audio signal characteristics. This dynamic adaptation maintains relatively simple device architecture while significantly improving versatility in handling different audio conditions.
Solution Approach 2:
The system changes the parameter of distribution matrix selection based on audio conditions. Instead of using a single fixed matrix, the system switches between different matrix configurations (transient-optimized and non-transient-optimized) depending on the detected signal characteristics. This parameter-based adaptation allows the system to maintain low complexity by using pre-defined matrices while achieving high adaptability through conditional selection.
Data Source
AI summary
An audio processing system, such as an upmixer, may be capable of separating diffuse and non-diffuse portions of N input audio signals. The upmixer may be capable of detecting instances of transient audio signal conditions. During instances of transient audio signal conditions, the up-mixer may be capable of adding a signal-adaptive control to a diffuse signal expansion process in which M audio signals are output. The upmixer may vary the diffuse signal expansion process over time such that during instances of transient audio signal conditions the diffuse portions of audio signals may be distributed substantially only to output channels spatially close to the input channels. During instances of non-transient audio signal conditions, the diffuse portions of audio signals may be distributed in a substantially uniform manner.