Headphone Early Reflection Synthesis for Natural 5.1 Downmix
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for down-mixing 5.1 channel audio signals to 2-channel signals for headphones output result in high computation time and unnatural sound due to lack of consideration for interaural time difference and frequency characteristics, leading to unnatural early reflections.
Innovation Solution
An apparatus and method that utilize an early reflection synthesizer with low computation time to generate pairs of early reflections considering interaural time difference (ITD) between channels, incorporating a head-related transfer function (HRTF) unit, diffusing unit with all-pass filters, and a reverberating unit to produce natural 5.1 channel sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional down-mixing methods are used to output 5.1 channel sound through headphones, then the system is simple to implement, but the sound quality becomes unnatural due to lack of interaural time difference consideration
Solution Approach 1:
The patent segments the audio processing into distinct functional blocks: direct sound generator, early reflection generator, and reverberation generator. Each block handles specific acoustic components separately, allowing precise control over interaural time differences and reflection characteristics while maintaining overall system simplicity
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing head-related impulse responses (HRIRs) for different reflection paths and directions. These pre-computed responses are then convolved with audio signals during playback, eliminating the need for complex real-time calculations while preserving natural sound characteristics
2Manufacturing precision
If binaural impulse response convolution is applied to all speakers, then natural sound localization is achieved, but computation time and memory usage increase significantly
Solution Approach 1:
The patent extracts and processes only the early reflection components separately from the direct sound and reverberation. By isolating the early reflection generation to specific time windows and using simplified models for these components, the computation time is significantly reduced while maintaining natural sound characteristics
Solution Approach 2:
The patent applies partial action by convolving binaural impulse responses only for the direct sound and reverberation components, while using a simplified early reflection model. This selective application of complex processing where most needed reduces overall computation time while maintaining sound quality
3Device complexity
If early reflections are generated without considering interaural time difference, then computation is simpler, but unnatural sound groups are formed
Solution Approach 1:
The patent applies local quality by implementing different processing characteristics for different audio components: early reflections include ITD to match specific spatial positions, while direct sound and reverberation use their own optimized processing. This localized differentiation creates natural sound groups without excessive overall complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively down-mixes 5.1 channel audio signals to 2-channel signals for headphones, achieving a natural 5.1 channel effect with reduced computation time and improved reflection density, mimicking real room reflections.
Implementation Method 1
an interaural time difference (ITD) generating unit for generating an interaural time difference (ITD) between the two audio signals
Implementation Method 2
a diffusing unit for filtering the two audio signals output from the HRTF unit through all-pass filters (APFs)
Implementation Method 3
a reverberating unit for exchanging the two audio signals output from the diffusing unit when they are received as feedback
Implementation Method 4
a direct sound generator for convoluting a head related transfer function (HRTF) to a plurality of audio signals
Data Source
AI summary
A stereophonic sound output apparatus and an early reflection generation method thereof. The stereophonic sound output apparatus includes an early reflection generator to implement an early reflection when a 5.1 channel audio signal is down-mixed to a 2-channel audio signal to play back a 5.1 channel audio signal through a 2-channel headphone. The early reflection generator generates early reflections in pairs in which there is an appropriate time difference between the left side reflections and the right side reflections by generating an interaural time difference between two input audio signals and filtering. It is possible to copy the characteristics of early reflections in a real listening room. It is also possible to implement an early reflection similar to a real reflection measured in an apparatus for playing back the 5.1 channel audio signal through 2-channel headphone. A natural 5.1 channel effect may also be obtained using little computation.