Audio Decoder Zero-Input Response for Smooth Mode Transitions

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing audio codecs face challenges in achieving smooth transitions between CELP-based and MDCT-based coding schemes, leading to issues like aliasing and discontinuities due to differences in coding domains, which existing solutions often introduce delays or require significant additional bitrates.

Innovation Solution

An audio decoder that utilizes a transition processor to modify decoded audio information using a zero-input response of a linear predictive filter, considering both initial states of the first and second decoded audio information to achieve a smooth transition without additional delay or increased bitrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a CELP-based coding concept is used for speech signals, then coding quality and bitrate efficiency are improved, but discontinuities and artifacts are introduced when switching to MDCT-based coding

Engineering Contradiction:

Improvecoding qualityVSAvoiddiscontinuities and artifacts

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by computing the zero-input response of the linear predictive filter in advance, based on the initial state derived from the CELP decoded audio information. This pre-computed zero-input response is then used to modify the MDCT decoded audio information at the transition point, ensuring smooth continuity without requiring additional delay or increased bitrate.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If transition processing is applied to smooth CELP-to-MDCT transitions, then audio quality is improved, but processing delay is introduced

Engineering Contradiction:

Improveaudio qualityVSAvoidprocessing delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent employs self-service by utilizing the zero-input response of the linear predictive filter, which is computed from the initial state derived from the CELP decoded audio information itself. This self-computed response is then applied to modify the MDCT decoded audio information, achieving smooth transitions without requiring external additional processing or introducing extra delay.

Inventive Principle:

Principle #25Self-service

3Reliability

If additional processing is used to handle mode transitions, then transition smoothness is improved, but computational complexity increases

Engineering Contradiction:

Improvetransition smoothnessVSAvoidcomputational complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the essential information needed for transition smoothing by computing the zero-input response from the initial state derived from the CELP decoded audio information. This extracted zero-input response is then applied to modify the MDCT decoded audio information, achieving smooth transitions with minimal additional computational complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If mode switching between CELP and MDCT is implemented, then coding adaptability is improved, but aliasing and discontinuities occur at transition boundaries

Engineering Contradiction:

Improvecoding adaptabilityVSAvoidaliasing and discontinuities

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an intermediary approach by computing the zero-input response of the linear predictive filter as a bridge between the CELP and MDCT coding modes. This zero-input response, derived from the initial state of the CELP decoded audio information, is then used to modify the MDCT decoded audio information at the transition point, ensuring smooth continuity and eliminating aliasing and discontinuities while maintaining coding adaptability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250299686A1Audio decoder, method and computer program using a zero-input-response to obtain a smooth transition

Publication Date: 2025.09.25 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

An audio decoder is disclosed. In one example, the audio decoder is for providing a decoded audio information on the basis of an encoded audio information includes a linear-prediction-domain decoder configured to provide a first decoded audio information on the basis of an audio frame encoded in a linear prediction domain, a frequency domain decoder configured to provide a second decoded audio information on the basis of an audio frame encoded in a frequency domain, and a transition processor. The transition processor is configured to obtain a zero-input-response of a linear predictive filtering, wherein an initial state of the linear predictive filtering is defined depending on the first decoded audio information and the second decoded audio information, and modify the second decoded audio information depending on the zero-input-response, to obtain a smooth transition between the first and the modified second decoded audio information.