Multi-Overlap Windowing for Low-Delay Transient Audio Coding

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Solution Overview

Problem

Conventional audio or image coding systems face challenges in minimizing look-ahead delay while maintaining high coding quality, particularly in low-delay communication applications, due to restricted window lengths and inefficiencies in handling transients, leading to pre-echo and post-echo noise.

Innovation Solution

The implementation of a multi-overlap window sequence with three overlapping windows of different lengths, allowing for adaptive overlap width selection based on transient location, which reduces look-ahead delay and minimizes pre-echo noise by ensuring only one window contains the transient, thereby optimizing coding efficiency and quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional window functions with restricted lengths are used, then device complexity is reduced, but transient handling quality deteriorates causing pre-echo and post-echo noise

Engineering Contradiction:

Improvewindow function structureVSAvoidpre-echo and post-echo noise

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent divides the signal processing into multiple overlapping windows (first, second, and third windows) with different lengths and overlap widths. Each window processes a specific portion of the signal, allowing the system to handle transients effectively by selecting appropriate window configurations without requiring a single complex window function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic adaptation of overlap widths between windows based on transient detection. The system adjusts the overlap width between the first and second windows, as well as between the second and third windows, according to the detected transient location, enabling flexible response to varying signal characteristics while maintaining manageable device complexity.

Inventive Principle:

Principle #15Dynamics

2Speed

If look-ahead delay is reduced for low-delay communication, then speed is improved, but transient detection accuracy deteriorates

Engineering Contradiction:

Improvecoding delayVSAvoidtransient location detection accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent performs preliminary transient detection within a reduced look-ahead region using the multi-window structure. By detecting transients in the upcoming frame with the help of multiple overlapping windows and adjusting overlap widths accordingly, the system prepares the coding parameters in advance within the available look-ahead delay, enabling low-delay operation while maintaining adequate transient detection accuracy.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If adaptive overlap width selection is implemented, then coding quality is improved, but device complexity increases

Engineering Contradiction:

Improvecoding quality and pre-echo minimizationVSAvoidwindow sequence control

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies different overlap widths locally between adjacent windows based on transient location. Specifically, the overlap width between the first and second windows, and between the second and third windows, is adapted independently according to where transients are detected. This localized adaptation improves coding quality and minimizes pre-echo noise without requiring global complexity increases.

Inventive Principle:

Principle #3Local quality

4Object-affected harmful factors

If multiple overlapping windows of different lengths are used, then transient handling is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvetransient coding qualityVSAvoidoverlap width accuracy

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent changes the overlap width parameter between windows as an adaptive control variable. By adjusting the overlap width between the first and second windows, and between the second and third windows, based on transient detection results, the system optimizes transient handling quality. This parameter adaptation allows flexible response to transients while maintaining implementable precision requirements.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10832694B2Apparatus and method for generating an encoded signal or for decoding an encoded audio signal using a multi overlap portion

Publication Date: 2020.11.10 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

An apparatus for generating an encoded signal includes: a window sequence controller for generating a window sequence information for windowing an audio or image signal, the window sequence information indicating a first window for generating a first frame of spectral values, a second window function and at least one third window function for generating a second frame of spectral values, wherein the first window function, the second window function and the one or more third window functions overlap within a multi-overlap region; a preprocessor for windowing a second block of samples corresponding to the second window function and the at least one third window functions using an auxiliary window function to acquire a second block of windowed samples, a spectrum converter for applying an aliasing-introducing transform; and a processor for processing the first frame and the second frame to acquire encoded frames of the audio or image signal.