Audio Limiter Gain Contours for Low-Latency Clipping Control
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Solution Overview
Problem
Existing digital signal processing methods for mitigating hard clipping in audio signals often introduce latency or modify non-clipped signal portions, leading to unpleasant distortion and potential damage to audio circuitry.
Innovation Solution
The method employs a soft limiting function using block-wise oversampling to determine dynamic gain values, applying an instant gain ascent and smooth gain decay in a forward and backward pass to generate preliminary and final gain contours, thereby avoiding additional latency and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a delay is introduced into the audio signal to look ahead and dynamically adjust attenuation, then clipping is prevented, but latency increases causing signal degradation and reduced interactivity
Solution Approach 1:
The patent applies preliminary action by performing a backward pass through the audio signal blocks to pre-calculate gain contours before the forward processing pass. This allows the system to anticipate peak levels and prepare appropriate attenuation values in advance, enabling real-time clipping prevention without introducing additional latency to the main signal path.
2Object-generated harmful factors
If soft clipping with wave shaping function is used to avoid hard clipping, then distortion is reduced and sound is more pleasant, but non-clipped signal portions are modified
Solution Approach 1:
The patent applies local quality by implementing dynamic range compression only in the local regions where signal peaks exceed the clipping threshold. The backward pass identifies specific blocks containing peaks and calculates targeted gain contours, applying attenuation only where necessary rather than uniformly modifying the entire signal. This preserves the original character of non-clipped portions while preventing distortion at peak levels.
3Loss of time
If block-wise oversampling is used for soft limiting, then additional latency is avoided and real-time processing is enabled, but processing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the audio signal into discrete blocks and processing each block independently through the backward and forward passes. This block-wise approach allows the system to work with manageable data segments, reducing memory requirements and computational overhead compared to processing the entire signal stream at once, while still achieving real-time performance.
Data Source
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Figure 1III-A~1IV-B
Figure 2I-A~2II-B
AI summary
Disclosed are systems and methods for processing an audio signal. In particular, there is provided a method for determining dynamic gain values to be applied on a digital input signal. The digital signal may be arranged in blocks. The dynamic gain values may be used for attenuating input signal values exceeding a clipping threshold. More particularly, the method comprising, for each signal block, passing backwards over the next signal block and the current signal block to produce a preliminary gain contour from the input signal; and passing forwards over the current signal block to produce a final gain contour for the current signal block based on the preliminary gain contour, wherein the gain contours are produced by applying an instant gain ascent and a smooth gain decay to the gain contours.