Audio Playback Synchronization via Virtual Clock
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Solution Overview
Problem
Existing methods for synchronized audio or video playback in peer-to-peer computer networks lack accuracy and often require synchronized system clocks or specialized hardware, leading to imprecise synchronization.
Innovation Solution
The implementation of a virtual clock system that synchronizes audio/video devices without relying on primary system clocks, using a virtual clock driven by the audio codec, which allows for direct synchronization and fine-tuning of playback rates, eliminating the need for system clock adjustments and specialized hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If system clocks are synchronized across devices, then playback synchronization can be achieved, but synchronization accuracy deteriorates due to system clock drift and lack of precision
Solution Approach 1:
The patent introduces a dedicated audio clock as an intermediary timing source that operates independently from system clocks. Each device generates its own audio clock based on local audio codec timing, serving as a mediator that provides precise time references for audio playback without relying on inaccurate system clock synchronization across the network.
Solution Approach 2:
The patent separates the timing function into distinct components: system clocks for general operations and dedicated audio clocks for audio playback synchronization. This segmentation allows each clock type to optimize for its specific purpose, with audio clocks providing high-precision timing independent of system clock drift and inaccuracies.
2Reliability
If dedicated hardware is used for each node, then synchronization accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent enables each device to generate its own audio clock independently using its existing audio codec hardware. Each node serves itself by creating local timing references from its audio codec's inherent timing signals, eliminating the need for external dedicated synchronization hardware while maintaining high synchronization accuracy through software-based clock management.
Solution Approach 2:
The patent makes existing audio codec hardware perform multiple functions: its primary audio processing role plus generating precise timing signals for synchronization. This multi-functionality allows standard audio hardware to serve as the timing source, eliminating the need for separate dedicated synchronization hardware at each node.
3Reliability
If system clock adjustments are made for synchronization, then playback coordination improves, but audio playback quality deteriorates due to resampling and processing interruptions
Solution Approach 1:
Instead of adjusting audio playback to match system clocks, the patent inverts the approach by having devices adjust their virtual clock representations to match remote audio clocks. This allows audio playback to continue at its native high quality without resampling, while synchronization is achieved through virtual clock time adjustments rather than audio signal processing changes.
4Measurement precision
If virtual clocks are used independent of system clocks, then synchronization accuracy improves, but system complexity increases
Solution Approach 1:
The patent introduces a virtual clock as a software-based intermediary that bridges local audio codec timing and remote device timing. This virtual clock layer provides precise time tracking and synchronization calculations without requiring changes to the underlying hardware or system clock infrastructure, managing complexity through software abstractions.
Data Source
AI summary
A method is provided for synchronizing playback of audio an/or video by a plurality of separate devices in a computer network. Each separate device generates a virtual clock in response to a timing of the audio codec of a received audio stream. Either the virtual clock is generated directly in response to the tick counter of the audio codec, or by a periodic measurement of the timing of the audio codec interpolated by a monotonic clock. A sample rate converter may be used to slightly adjust the frequency of the virtual clock.