Audio Encoder Switching Between Time and Frequency Domains

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing audio coding technologies face inefficiencies when switching between time-domain and frequency-domain coding modes, leading to increased data overhead and artifacts due to non-critical sampling and steep overlap regions, which compromise coding efficiency and audio quality.

Innovation Solution

An improved audio coding concept that employs a controller to manage switching between time-domain and frequency-domain encoders and decoders using modified framing and windowing techniques, such as aliasing-free start and stop windows, to minimize overhead and ensure smooth transitions between coding domains.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If switching between time-domain and frequency-domain coding modes is implemented, then coding efficiency for different audio signals is improved, but data overhead and artifacts increase

Engineering Contradiction:

Improvecoding efficiencyVSAvoiddata overhead

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent applies preliminary action by pre-calculating and storing aliasing-free window functions and their corresponding framing structures before actual audio encoding. The encoder prepares transition frameworks in advance that define how to switch between time-domain and frequency-domain modes without generating artifacts, thus avoiding the need to compute these complex parameters during real-time encoding when switching occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary transition mechanism that mediates between time-domain and frequency-domain coding modes. This intermediary framework includes specially designed aliasing-free window functions that act as buffers during mode switching, preventing direct abrupt transitions that would cause artifacts and overhead. The intermediary structure smooths the transition while maintaining coding efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If switching between time-domain and frequency-domain coding modes is implemented, then coding efficiency for different audio signals is improved, but artifacts are generated due to non-critical sampling

Engineering Contradiction:

Improvecoding efficiencyVSAvoidartifacts

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of aliasing during mode transitions into a beneficial feature by designing aliasing-free window functions that intentionally introduce controlled time-domain aliasing cancellation. This controlled aliasing mechanism, when applied with the specific framing structures defined in the patent, actually eliminates artifacts during switching while maintaining the efficiency benefits of multi-domain coding.

Inventive Principle:

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

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting window function parameters and framing structures based on the current coding mode and transition state. When switching between time-domain and frequency-domain modes, the system modifies parameters such as window length, overlap regions, and sampling rates to ensure artifact-free transitions while maintaining optimal coding efficiency for the target mode.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If traditional overlap regions are used during mode switching, then smooth transitions are achieved, but the region size must be large compromising coding efficiency

Engineering Contradiction:

Improvetransition smoothnessVSAvoidcoding efficiency

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent applies local quality by making the overlap region size and window function characteristics location-dependent within the audio signal. Instead of using a uniformly large overlap region throughout, the system applies different windowing strategies and overlap lengths based on the local signal characteristics and the specific transition point, thus achieving smooth transitions only where necessary while maintaining coding efficiency in other regions.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP3002750B1Audio encoder and decoder for encoding and decoding audio samples

Publication Date: 2017.11.08 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

Figure 1A
Figure 1B
Figure 2a~2j

AI summary

An audio encoder (100) for encoding audio samples, comprising a first time domain aliasing introducing encoder (110) for decoding audio samples in a first encoding domain, the first time domain aliasing introducing encoder (110) having a first framing rule, a start window and a stop window. The audio encoder (100) further comprises a second encoder (120) for encoding samples in a second encoding domain, the second encoder (120) having a predetermined frame size number of audio samples, and a coding warm-up period number of audio samples, the second encoder (120) having a different second framing rule, a frame of the second encoder (120) being an encoded representation of a number of timely subsequent audio samples, the number being equal to the predetermined frame size number of audio samples. The audio encoder (100) further comprises a controller (130) switching from the first encoder (110) to the second encoder (120) in response to characteristic of the audio samples, and for modifying the second framing rule in response to switching from the first encoder (110) to the second encoder (120) or for modifying the start window or the stop window of the first encoder (110), wherein the second framing rule remains unmodified.