Audio Playback Volume Limiting With Limiter Feedback Control
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Solution Overview
Problem
Conventional methods for limiting volume in media playback devices often result in a choppy listening experience due to the interaction between dynamic bass control and limiters, leading to unnatural bass reduction and over-limiting, which can sacrifice desirable bass levels for operational safety.
Innovation Solution
A feedback controller is introduced that receives a gain reduction value from the limiter and provides a feedback signal to an upstream gain stage, applying separate filters with varying time constants to achieve balanced dynamic gain reduction and minimize audible artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic bass control and limiter are used together to protect operational limits, then reliability is improved, but manufacturing precision deteriorates due to over-limiting and unnatural bass reduction
Solution Approach 1:
The patent implements a feedback controller that receives the output signal from the limiter and feeds back control signals to the dynamic bass control module. This feedback mechanism allows the system to monitor the limiter's gain reduction actions and adjust the dynamic bass control accordingly, preventing over-limiting while maintaining operational safety. The feedback loop ensures that bass reduction is natural and proportional to actual operational needs rather than excessive.
Solution Approach 2:
The system performs preliminary bass control through the dynamic bass control module before the signal reaches the limiter. By pre-adjusting bass levels based on predicted operational conditions and feedback from previous cycles, the system reduces the likelihood that the limiter will need to apply aggressive gain reduction, thereby maintaining both reliability and bass level accuracy.
2Reliability
If aggressive limiting is applied to prevent operational limits, then reliability is improved, but audio quality deteriorates due to choppy listening experience and audible artifacts
Solution Approach 1:
The feedback controller continuously monitors the limiter's output and adjusts the dynamic bass control in real-time to prevent the limiter from applying aggressive gain reduction. This feedback mechanism smooths out abrupt volume changes and prevents the choppy listening experience and audible artifacts that result from aggressive limiting, while still ensuring operational safety is maintained.
Solution Approach 2:
The system employs dynamic adjustment of bass control parameters based on real-time feedback from the limiter. Rather than applying static or overly aggressive limiting thresholds, the system dynamically adapts its control strategy to match the actual signal conditions, resulting in smoother transitions and fewer audible artifacts while maintaining operational reliability.
Data Source
AI summary
Systems and methods for limiting volume in an audio playback device using a feedback controller are disclosed herein. In one example, a gain stage modulates gain of an audio signal based in part on feedback from a downstream limiter. The gain stage receives a first audio signal as well as a feedback signal from the feedback controller. Based at least in part on the feedback signal from the feedback controller, the gain stage modulates a gain of the first audio signal to provide a second audio signal. The second audio signal is delivered to the limiter, which limits the second audio signal to produce an output signal. The output signal is played back via a transducer. The feedback controller receives a gain reduction value from the limiter and determines a feedback signal to provide to the gain stage upstream of the limiter.