Audio Track Boundary Sample Ramping for Artifact Reduction

Solution Overview

Problem

Audio processing techniques, particularly in spatial audio rendering, create audible artifacts at the boundaries of temporally-adjacent audio tracks due to signal discontinuities, which degrade the perceived quality of gapless audio.

Innovation Solution

Applying ramp signals to adjust the samples at the ends of adjacent audio tracks to ensure continuity, optionally with limiting functions to maintain valid sample values, and trimming or zero-filling to mitigate discontinuities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If filtering and spatial audio processing operations are applied to audio tracks, then audio quality and spatial effect are improved, but audible artifacts and discontinuities are created at track boundaries

Engineering Contradiction:

Improveaudio qualityVSAvoidaudible artifacts

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by modifying audio samples at the boundaries of tracks before the discontinuity problem occurs. Specifically, samples at the end of a first track and the beginning of a second track are pre-adjusted to ensure continuity when the tracks are concatenated, preventing audible artifacts from arising in the first place

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary approach by introducing a boundary modification process that acts as a mediator between adjacent tracks. This intermediary process adjusts the boundary samples to create a smooth transition, effectively bridging the gap between tracks that would otherwise be discontinuous

Inventive Principle:

Principle #24Intermediary (Mediator)

2Duration of action of moving object

If audio tracks are concatenated for gapless audio, then continuous playback is achieved, but discontinuities at boundaries create audible artifacts

Engineering Contradiction:

Improvecontinuous playbackVSAvoidaudible artifacts

Core Design Contradiction:

Duration of action of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by modifying audio samples at the boundaries of tracks before the discontinuity problem occurs. Specifically, samples at the end of a first track and the beginning of a second track are pre-adjusted to ensure continuity when the tracks are concatenated, preventing audible artifacts from arising in the first place

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuity of useful action by ensuring that the audio signal remains continuous across track boundaries. The boundary modification process preserves the continuous playback experience while eliminating the harmful discontinuities that would otherwise occur at the junction points of concatenated tracks

Inventive Principle:

Principle #20Continuity of useful action

3Adaptability or versatility

If filtering operations are applied to audio content, then spatial audio effect is achieved, but artifacts are created at track boundaries

Engineering Contradiction:

Improvespatial audio effectVSAvoidartifacts

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by modifying audio samples at the boundaries of tracks before the discontinuity problem occurs. Specifically, samples at the end of a first track and the beginning of a second track are pre-adjusted to ensure continuity when the tracks are concatenated, preventing audible artifacts from arising in the first place

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies local quality by treating the boundary regions of tracks differently from the interior regions. The boundary modification process applies specific adjustments only to samples at the beginning and end of tracks, leaving the interior samples unchanged, thus maintaining the spatial audio effect while locally correcting the boundary artifacts

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12457464B2Artifact reduction on transitions between audio tracks

Publication Date: 2025.10.28 APPLE INC

AI summary

An audio artifact reduction technique operates on a pair of temporally-adjacent audio tracks. Samples at an end portion of a first track may be altered according to an inter-track sample discontinuity at a boundary between the two tracks. Samples at a beginning portion of a second track also may be altered according to the inter-track discontinuity. These altering operations may cause the sample values and the end of the first track and the beginning of the second track to be equal to each other at the boundary between the two tracks. In one aspect, the altering may generate adjustment curves that alter sample values of the tracks around the boundary between them. In another aspect, the altering may trim the tracks at zero crossings of track sample values nearest to the boundary between the tracks.