Audio Decoder Insertion Window for Domain Transition

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Solution Overview

Problem

Existing audio coding technologies face challenges in seamlessly transitioning between frequency-domain and linear-prediction-domain modes, particularly in efficiently encoding background noise during short breaks between words, which leads to either high bitrate inefficiency or inaccurate encoding.

Innovation Solution

An audio decoder is designed with a linear-prediction-domain decoder core and a frequency-domain decoder core, using an insertion window to smoothly transition between audio frames, allowing for the insertion of a frequency-domain-encoded frame between linear-prediction-domain-encoded frames, thereby enabling efficient encoding and decoding of background noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a single frequency-domain-encoded audio frame is inserted between two linear-prediction-domain-encoded audio frames, then bitrate efficiency is improved, but transition smoothness deteriorates

Engineering Contradiction:

Improvebitrate efficiencyVSAvoidtransition smoothness

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

A dedicated insertion window is introduced as an intermediary element to mediate the transition between frequency-domain and linear-prediction-domain encoded frames. This insertion window serves as a bridge that enables smooth transitions while maintaining the benefits of frequency-domain encoding for background noise, thus resolving the contradiction between bitrate efficiency and transition smoothness.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Different windowing strategies are applied to different parts of the audio signal depending on the encoding domain. Specifically, a first window is applied to linear-prediction-domain frames and a second window is applied to frequency-domain frames, allowing each region to be optimized for its specific encoding type while maintaining overall transition smoothness.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If frequency-domain encoding is used for background noise during short breaks, then encoding accuracy is improved, but device complexity increases

Engineering Contradiction:

Improveencoding accuracyVSAvoiddecoder complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The decoder dynamically switches between different decoding modes based on the encoding domain of the incoming audio frames. The system can adaptively select between linear-prediction-domain decoding and frequency-domain decoding, allowing accurate encoding of background noise while managing computational complexity through selective processing.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The audio signal is segmented into different encoding domains based on content characteristics. Background noise during short breaks is encoded in the frequency domain with higher accuracy, while speech portions use linear-prediction-domain encoding, allowing the system to manage complexity by processing different segments with appropriate methods.

Inventive Principle:

Principle #1Segmentation

3Reliability

If linear-prediction-domain encoding is used for speech, then speech quality is maintained, but background noise encoding becomes inaccurate

Engineering Contradiction:

Improvespeech qualityVSAvoidbackground noise encoding accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

Different encoding domains are applied to different parts of the audio signal based on content type. Linear-prediction-domain encoding is used for speech portions to maintain speech quality, while frequency-domain encoding is used for background noise portions to improve encoding accuracy, thus resolving the contradiction through localized optimization.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The encoding parameters are changed based on the audio content characteristics. The system switches between linear-prediction-domain and frequency-domain encoding by changing the fundamental encoding parameters, allowing optimal encoding for each type of audio content while maintaining overall system performance.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2214164B1Audio decoder, methods for decoding an audio signal and computer program

Publication Date: 2017.08.02 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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AI summary

An audio decoder for providing a decoded representation of an audio content on the basis of an encoded representation of the audio content comprises a linear-prediction-domain decoder core configured to provide a time-domain representation of an audio frame on the basis of a set of linear-prediction domain parameters associated with the audio frame and a frequency-domain decoder core configured to provide a time-domain representation of an audio frame on the basis of a set of frequency-domain parameters, taking into account a transform window out of a set comprising a plurality of different transform windows. The audio decoder comprises a signal combiner configured to overlap-and-add-time-domain representations of subsequent audio frames encoded in different domains, in order to smoothen a transition between the time-domain representations of the subsequent frames. The set of transform windows comprises one or more windows specifically adapted for a transition between a frequency-domain core mode and a linear-prediction-domain core mode.