Interleaved Audio Coding for Transform Length Switching

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing frequency-domain audio codecs struggle to achieve satisfactory quality at low bitrates for audio signals with prominent transients, such as rain or applause, due to issues like time-smearing and increased data overhead when using either long or short block coding.

Innovation Solution

A frequency-domain audio codec that supports transform length switching, allowing for interleaved transmission of frequency-domain coefficients and independent extraction of coefficients and scale factors, enabling compatibility with existing codecs while improving quality for certain audio signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If long block coding is used, then spectral efficiency is improved, but time-smearing of coding errors (pre-echo) increases

Engineering Contradiction:

Improvespectral efficiencyVSAvoidtime-smearing of coding errors

Core Design Contradiction:

Loss of informationVSObject-affected harmful factors

Solution Approach 1:

The audio signal is divided into multiple short blocks within a single frame, allowing the codec to achieve better temporal resolution and reduce pre-echo effects while maintaining spectral efficiency through the segmented transform approach

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If short block coding is used, then time-smearing is reduced, but data overhead increases leading to spectral holes

Engineering Contradiction:

Improvetime-smearing reductionVSAvoiddata overhead

Core Design Contradiction:

Object-affected harmful factorsVSQuantity of substance

Solution Approach 1:

Multiple short block transforms are merged into a unified frame structure with interleaved coefficient transmission, reducing the overall data overhead while maintaining the temporal resolution benefits of short blocks

Inventive Principle:

Principle #5Merging (Combining)

3Manufacturing precision

If a new frequency-domain audio codec is built to support additional transform lengths, then coding quality for transient signals is improved, but compatibility with existing codecs is lost

Engineering Contradiction:

Improvecoding qualityVSAvoidbackward compatibility

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The codec is designed with multi-functionality to support both traditional long/short block coding and the new transform length switching capability, allowing it to maintain backward compatibility while providing improved coding quality for transient signals

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The codec dynamically switches between different transform lengths based on signal characteristics, enabling adaptive optimization of coding quality while maintaining compatibility with existing decoders through proper signalization

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12488804B2Frequency-domain audio coding supporting transform length switching

Publication Date: 2025.12.02 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A frequency-domain audio codec is provided with the ability to additionally support a certain transform length in a backward-compatible manner, by the following: the frequency-domain coefficients of a respective frame are transmitted in an interleaved manner irrespective of the signalization signaling for the frames as to which transform length actually applies, and additionally the frequency-domain coefficient extraction and the scale factor extraction operate independent from the signalization. By this measure, old-fashioned frequency-domain audio coders/decoders, insensitive for the signalization, would be able to nevertheless operate without faults and with reproducing a reasonable quality. Concurrently, frequency-domain audio coders/decoders able to support the additional transform length would offer even better quality despite the backward compatibility. As far as coding efficiency penalties due to the coding of the frequency domain coefficients in a manner transparent for older decoders are concerned, same are of comparatively minor nature due to the interleaving.