Audio Dynamic Range Compression With Fewer Pumping Artifacts
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Solution Overview
Problem
Dynamic range compression technologies often introduce undesirable artifacts such as 'pumping' and 'breathing' in audio signals, particularly when applied to well-compressed signals or those with regular transients, leading to a loss of quiet elements and distortion.
Innovation Solution
Implementing a dynamic range compression method that applies reduced or no compression when the average loudness of an audio signal approaches a target level, using a slow smoother to determine average loudness over a longer time frame, and adjusting release time constants based on loudness slopes and transient presence to minimize artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dynamic range compression is applied to increase loudness of low-level signals, then average loudness is improved, but pumping and breathing artifacts are introduced
Solution Approach 1:
The patent implements dynamic adjustment of the release time constant based on the detected transient presence in the audio signal. When transients are detected, the release time constant is increased (slowed down) to prevent pumping artifacts. This dynamic adaptation allows the compressor to optimize between loudness enhancement and artifact prevention in real-time根据不同信号特征调整参数
Solution Approach 2:
The system continuously monitors the audio signal for transient events and uses this feedback to adjust the release time constant. The transient detection mechanism provides real-time feedback about signal characteristics, enabling the compressor to adapt its behavior and prevent artifacts while maintaining loudness benefits
2Speed
If attack and release times are shortened to respond quickly to signal changes, then responsiveness is improved, but distortion and loss of quiet elements occur
Solution Approach 1:
The patent dynamically adjusts the release time constant based on transient detection. During transient periods, the release time is extended to prevent distortion and preserve quiet elements. During non-transient periods, faster release times can be used for improved responsiveness. This creates optimal performance across different signal conditions
Solution Approach 2:
The system changes the release time constant parameter in response to detected transients. By modifying this key parameter based on signal characteristics, the compressor achieves both fast response when appropriate and artifact prevention when needed, resolving the contradiction between speed and quality
3Object-generated harmful factors
If smoothing is applied to reduce gain fluctuations, then artifact prevention is improved, but attack and release times increase
Solution Approach 1:
The patent makes the smoothing time constant dynamic by adjusting it based on transient detection. During transient events, stronger smoothing is applied to prevent artifacts. During normal periods, less smoothing is applied to maintain faster response times. This dynamic approach resolves the trade-off between artifact reduction and time efficiency
Data Source
AI summary
Methods for performing dynamic range compression (DRC) on audio in a manner intended to produce output audio for playback by systems or devices with limited power handling capabilities and preferably also to reduce or prevent undesirable artifacts (e.g., pumping and/or breathing) in the output audio. Some embodiments perform the DRC so as to maximize average loudness (while preventing loss of quieter elements) during playback, and also to reduce or prevent distortion. Other aspects are systems or devices configured to perform embodiments of the method. In some embodiments, reduced DRC is applied when average loudness of the input audio approaches (or matches or exceeds) a target (e.g., a knee point for DRC, or a signal level near to a maximum playback level of the intended playback system), since such input audio is assumed to have already been compressed, and otherwise applying full DRC to the input audio.