Adaptive Audio Gain Control for Artifact-Free Volume Normalization
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Solution Overview
Problem
Existing digital volume normalization techniques for media streams are ineffective and introduce audible artifacts, making it inconvenient for users to switch between media streams with different baseline volumes during place-shifting applications.
Innovation Solution
An adaptive gain control method for digital audio samples that initializes with a fast gain adaptation scheme using variable weighting factors, transitioning to a steady state scheme with fixed weighting factors to normalize volume across media streams, ensuring consistent loudness perception without modifying the presentation device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If existing digital volume normalization techniques are applied to media streams, then volume adjustment capability is provided, but audible artifacts are introduced and normalization effectiveness deteriorates
Solution Approach 1:
The patent implements dynamic gain adaptation by transitioning from a fast adaptation scheme with variable weighting factors during initialization to a steady state scheme with fixed weighting factors during normal operation. This dynamic adjustment of the adaptation mechanism itself allows the system to respond quickly to volume changes while maintaining stability, thereby reducing audible artifacts compared to static normalization techniques.
Solution Approach 2:
The patent changes the weighting factors used in gain calculation from variable (during fast adaptation) to fixed (during steady state). This parameter change optimizes the normalization process by using aggressive variable weighting initially to quickly establish volume levels, then switching to stable fixed weighting to maintain consistent volume without introducing artifacts during normal playback.
2Speed
If fast gain adaptation with variable weighting factors is used during initialization, then adaptation speed is improved, but system complexity increases
Solution Approach 1:
The patent applies fast gain adaptation with variable weighting factors only during an initialization phase before switching to steady state operation. This preliminary action allows the system to quickly establish appropriate gain levels when needed (such as when switching between media streams), while avoiding the complexity of continuous variable weighting during normal operation.
Solution Approach 2:
The patent segments the gain adaptation process into two distinct phases: initialization phase using fast adaptation with variable weighting factors, and steady state phase using fixed weighting factors. This segmentation allows the system to apply complex variable weighting only when necessary for quick adaptation, while using simpler fixed weighting for the majority of operation time, thereby reducing overall system complexity.
3Stability of the object's composition
If steady state gain adaptation with fixed weighting factors is used, then system stability is improved, but adaptation responsiveness to content changes deteriorates
Solution Approach 1:
The patent makes the gain adaptation system dynamic by allowing it to switch between two operational modes: fast adaptation mode during initialization and steady state mode during normal operation. This dynamic switching enables the system to have both quick responsiveness when needed and stable predictable behavior during normal playback, resolving the contradiction between stability and adaptability.
Data Source
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AI summary
An adaptive gain control system and related operating method for digital audio samples is provided. The method is suitable for use with a digital media encoding system that transmits encoded media streams to a remotely-located presentation device such as a media player. The method begins by initializing the processing of a media stream. Then, the method adjusts the gain of a first set of digital audio samples in the media stream using a fast gain adaptation scheme, resulting in a first group of gain-adjusted digital audio samples having normalized volume during presentation. The method continues by adjusting the gain of a second set of digital audio samples in the media stream using a steady state gain adaptation scheme that is different than the fast gain adaptation scheme, resulting in a second group of gain-adjusted digital audio samples having normalized volume during presentation.