Audio Limiter Sidechain Filtering for Smooth Synchronous Playback
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Solution Overview
Problem
Conventional methods for maintaining operation of audio playback devices within their operational limits often result in a choppy listening experience, particularly with bass-heavy content, due to dynamic adjustments in filter characteristics.
Innovation Solution
A limiter system using dynamic sidechain filters (DSFs) that compare the envelopes of dry and wet audio signals to a threshold, dynamically adjusting the gain of these signals to maintain operation within the device's operational limits while minimizing distortion and choppiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic adjustments in filter characteristics are used to maintain operation within operational limits, then audio quality is improved, but listening experience becomes choppy
Solution Approach 1:
The patent employs dynamic sidechain filters that automatically adjust their characteristics in real-time based on the audio signal levels. The filter cutoff frequencies and gains are dynamically modified according to the instantaneous signal conditions, allowing the system to adapt to varying audio content while maintaining smooth operation without manual intervention or choppiness
Solution Approach 2:
The system uses feedback mechanisms where the output of the audio processing chain is monitored and fed back to the sidechain filters. This feedback loop allows the filters to continuously adjust their characteristics based on the actual signal levels and operational status, ensuring the playback device remains within operational limits while maintaining audio quality
2Reliability
If bass boosting is applied to enhance low frequency response, then audio quality is improved, but distortion increases at high volume settings
Solution Approach 1:
The patent applies preliminary limiting actions to the bass frequencies before they reach the playback device. By pre-processing the audio signal to control the amplitude of low-frequency content, the system prevents excessive bass levels that would cause distortion at high volume settings, while still maintaining enhanced bass response through controlled gain application
Solution Approach 2:
The system dynamically changes the gain parameter of the bass frequencies based on the operational status and signal levels. By adjusting the bass gain in real-time according to the audio content and device capabilities, the system maintains enhanced bass response while preventing the gain from reaching levels that would cause distortion
Data Source
AI summary
A computing device is configured to (i) receive an indication of an operational limit of a given playback device, where the given playback device is included in a group of at least two playback devices that are configured for synchronous playback of audio content, (ii) receive a first audio signal for playback by the group of at least two playback devices, (iii) based on the operational limit of the given playback device, apply a filter to the first audio signal to generate a second audio signal, and (iv) transmit the second audio signal to at least the given playback device for synchronous playback by the group of at least two playback devices.