Audio Codec Quantization for Dense Transient Event Detection
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Solution Overview
Problem
Perceptual or lossy audio codecs struggle with compressing dense transient events like applause, crackling fire, or rain, leading to increased computational complexity and loss of perceived audio quality.
Innovation Solution
Detecting dense transient events in audio signals and applying a special constant signal-to-noise ratio quantization noise shaping mode, conditioned on the detection results, to improve audio quality without significantly impacting other audio classes, using features already computed in perceptual audio encoders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional compression methods are applied to dense transient events, then compression efficiency is improved, but perceived audio quality deteriorates
Solution Approach 1:
The patent applies different quantization strategies to different audio content types. Dense transient events are detected and processed with a special constant signal-to-noise ratio quantization mode, while other audio content uses conventional quantization methods. This local differentiation resolves the contradiction by optimizing compression for transient events without compromising overall audio quality.
Solution Approach 2:
The patent changes the quantization parameter strategy based on audio content detection. When dense transient events are detected, the system switches to a constant signal-to-noise ratio quantization mode with adjusted quantization step sizes, rather than using the conventional variable bit-rate approach. This parameter adaptation improves compression efficiency for transient events while maintaining perceived audio quality.
2Productivity
If compression efficiency is increased for dense transient events, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent uses the perceptual entropy values and other features that are already computed during normal perceptual audio encoding to detect dense transient events. The encoder leverages its own existing computational outputs for detection purposes, avoiding the need for separate complex detection algorithms. This self-service approach improves compression efficiency for transient events without significantly increasing encoder complexity.
3Reliability
If special processing is applied to dense transient events, then perceived audio quality is improved, but device complexity increases
Solution Approach 1:
The patent makes the constant signal-to-noise ratio quantization mode and dense transient event detection features part of the AC-4 codec specification, allowing them to be used conditionally based on audio content. This universal approach enables the system to apply special processing only when needed (for dense transient events) while maintaining conventional processing for other content, improving perceived audio quality without permanently increasing device complexity.
Data Source
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AI summary
The present disclosure relates to methods and apparatus for audio coding. A method of encoding a portion of an audio signal comprises determining whether the portion of the audio signal is likely to contain dense transient events, and if it is determined that the portion of the audio signal is likely to contain dense transient events, quantizing the portion of the audio signal using a quantization 5 mode that applies a substantially constant signal-to-noise ratio over frequency for the portion of the audio signal. The present disclosure further relates to a method of detecting dense transient events in a portion of an audio signal.