Sub-Frame Gain Smoothing for Audio Ducking Artifacts
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Solution Overview
Problem
Large changes in ducking gain from frame to frame in audio bitstreams without sufficient smoothing lead to audible artifacts like the 'zipper' effect in decoded audio presentations, affecting the quality of main-associated audio experiences.
Innovation Solution
Implementing sub-frame gain smoothing operations using a built-in ramp in audio decoders, which calculates additional sub-frame gains over a specified time interval to smooth temporal changes in audio object gains, thereby reducing audible artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frame-level ducking gain changes are applied without smoothing, then the balance between main and associated audio can be controlled, but audible artifacts like zipper effect occur
Solution Approach 1:
The audio frame is segmented into multiple sub-frames, and the gain control is applied at the sub-frame level rather than the entire frame level. This allows for gradual gain transitions within the frame, preventing abrupt changes that cause zipper artifacts while maintaining the overall ducking gain control between main and associated audio programs.
2Adaptability or versatility
If large changes in ducking gain are applied from frame to frame, then the balance between main and associated audio can be adjusted, but audible degradations occur
Solution Approach 1:
The ramp length is predetermined and configured before audio processing occurs. This pre-configured ramp length determines the number of sub-frames over which gain changes will be distributed, allowing the system to prepare for smooth transitions in advance and prevent audible degradations before they occur.
Solution Approach 2:
The gain application becomes dynamic by distributing the gain change across multiple sub-frames rather than applying it instantaneously. The ramp length parameter allows the system to adapt the transition smoothness dynamically, balancing between rapid gain changes for audio balance control and smooth transitions for audio quality.
3Object-affected harmful factors
If sub-frame gain smoothing is implemented, then audible artifacts are reduced, but processing complexity increases
Solution Approach 1:
The audio renderer's existing ramp mechanism, originally designed for spatial movement smoothing, is made multi-functional by also using it for gain smoothing. This universal approach allows the same sub-frame processing infrastructure to handle both spatial and gain transitions, reducing the need for separate complex processing paths while still achieving artifact reduction.
Data Source
AI summary
An audio bitstream is decoded into audio objects and audio metadata for the audio objects. The audio objects include a specific audio object. The audio metadata specifies frame-level gains that include a first gain and a second gain respectively for a first audio frame and a second audio frame. It is determined, based on the first and second gains, whether sub-frame gains are to be generated for the specific audio object. If so, a ramp length is determined for a ramp used to generate the sub-frame gains for the specific audio object. The ramp of the ramp length is used to generate the sub-frame gains for the specific audio object. A sound field represented by the audio objects with the sub-frame gains is rendered by audio speakers.