Adaptive Low Frequency Compensation for Audio Encoding

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Solution Overview

Problem

Conventional audio encoding methods apply low frequency compensation uniformly to all signals, leading to suboptimal quality for both tonal and non-tonal signals, as they fail to distinguish between prominent low-frequency tonal content and non-tonal content, resulting in either degraded or improved perceived quality during decoding.

Innovation Solution

An adaptive low frequency compensation method that selectively applies low frequency compensation during encoding based on tonality detection, enabling it for signals with prominent low-frequency tonal components while disabling it for non-tonal signals, using tonality detection to generate compensation control data and adjust masking values accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If low frequency compensation is applied uniformly to all signals, then encoding quality for tonal signals is improved, but encoding quality for non-tonal signals deteriorates

Engineering Contradiction:

Improveencoding qualityVSAvoidsignal type adaptability

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic low frequency compensation by adjusting the compensation amount based on detected tonality characteristics of the input signal. The system transitions from a static, uniform compensation approach to a dynamic one where the compensation parameter varies according to the signal's tonal content, thereby optimizing encoding quality for both tonal and non-tonal signals.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies different encoding treatments to different frequency regions based on tonality detection. Specifically, low frequency compensation is applied selectively to bands with prominent tonal content while being reduced or disabled for non-tonal bands, creating a localized quality optimization strategy that adapts to the specific characteristics of each frequency region.

Inventive Principle:

Principle #3Local quality

2Loss of information

If low frequency compensation is enabled for all frequency bands, then bit allocation is optimized for tonal content, but bit allocation becomes suboptimal for non-tonal content

Engineering Contradiction:

Improveinformation preservationVSAvoidencoding efficiency

Core Design Contradiction:

Loss of informationVSProductivity

Solution Approach 1:

The patent changes the compensation parameter (low frequency compensation amount) based on the detected tonality of the signal. When tonal content is detected in low frequency bands, full compensation is applied; when non-tonal content is detected, the compensation parameter is reduced or disabled. This parameter adaptation optimizes bit allocation efficiency for the specific signal type being encoded.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent segments the frequency spectrum into tonal and non-tonal regions based on tonality detection results. Different bit allocation strategies are then applied to these segments: low frequency compensation is applied to tonal segments to preserve information, while non-tonal segments use standard bit allocation for optimal encoding efficiency.

Inventive Principle:

Principle #1Segmentation

3Manufacturing precision

If uniform low frequency compensation is applied, then perceived quality of tonal signals is enhanced, but perceived quality of non-tonal signals is degraded

Engineering Contradiction:

Improveperceived qualityVSAvoidquality degradation

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent dynamically adjusts the low frequency compensation level based on real-time tonality detection of the encoded signal. This dynamic adjustment ensures that perceived quality is enhanced for tonal signals through full compensation while preventing quality degradation for non-tonal signals by reducing or disabling compensation, thereby eliminating the harmful effect of uniform compensation across all signal types.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent converts the potentially harmful effect of uniform low frequency compensation (which degrades non-tonal signals) into a beneficial adaptive system. By detecting tonality characteristics, the system selectively applies compensation only where beneficial (tonal signals) and avoids it where harmful (non-tonal signals), thereby transforming a one-size-fits-all harmful approach into a targeted beneficial approach.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9275649B2Method and system for encoding audio data with adaptive low frequency compensation

Publication Date: 2016.03.01 DOLBY LABORATORIES LICENSING CORP

AI summary

A method for determining mantissa bit allocation of audio data values of frequency domain audio data to be encoded. The allocation method includes a step of determining masking values for the audio data values, including by performing adaptive low frequency compensation on the audio data of each frequency band of a set of low frequency bands of the audio data. The adaptive low frequency compensation includes steps of: performing tonality detection on the audio data to generate compensation control data indicative of whether each frequency band in the set of low frequency bands has prominent tonal content; and performing low frequency compensation on the audio data in each frequency band in the set of low frequency bands having prominent tonal content as indicated by the compensation control data, but not performing low frequency compensation on the audio data in any other frequency band in the set of low frequency bands.