Networked Audio Playback Synchronization Without a Central Clock
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Solution Overview
Problem
Existing audio systems with multiple rendering devices face challenges in synchronizing playback across zones without adding complexity, cost, and using excessive network bandwidth, as previous methods rely on centralized clock sources.
Innovation Solution
A system and method for synchronizing networked rendering devices by having a first device act as a zone leader, communicating current audio sample indices and transmission latency to synchronize playback across devices using local timing oscillators, eliminating the need for a centralized clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a centralized clock source is used to synchronize playback across multiple rendering devices, then synchronization accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the centralized clock source from the system architecture and replaces it with distributed local timing oscillators in each rendering device. Each device independently maintains its own timing reference, eliminating the need for complex centralized clock distribution infrastructure while achieving synchronization through peer-to-peer timestamp comparison and offset calculation.
Solution Approach 2:
The unified centralized clock function is segmented and distributed to individual rendering devices, each possessing its own local timing oscillator. This segmentation allows devices to operate independently with their own time references while still achieving coordinated synchronization through message exchange and offset adjustment, reducing overall system complexity.
2Measurement precision
If a centralized clock source is distributed among players, then synchronization is achieved, but network bandwidth consumption increases
Solution Approach 1:
Instead of continuously distributing clock signals at full bandwidth, the system uses partial action by exchanging only essential timestamp information and synchronization offsets between devices. This selective data exchange maintains synchronization accuracy while significantly reducing network bandwidth consumption compared to continuous clock signal distribution.
Solution Approach 2:
The patent uses timestamp copying and offset propagation rather than continuous clock signal distribution. Each device copies relevant timing information from peer devices and adjusts its local oscillator accordingly, achieving synchronization with minimal network traffic compared to distributing actual clock signals to all players.
3Device complexity
If independent timing oscillators are used in each device, then system complexity is reduced, but synchronization precision deteriorates
Solution Approach 1:
The system implements feedback mechanisms where each rendering device continuously monitors its synchronization status by comparing timestamps with peer devices. Based on this feedback, devices dynamically adjust their local timing oscillators to maintain accurate synchronization, compensating for drift and variations in independent oscillators while keeping system complexity low.
Solution Approach 2:
The patent employs dynamic timing adjustment where each device's local oscillator frequency and phase are continuously adapted based on real-time synchronization requirements. This dynamic behavior allows independent oscillators to maintain precise synchronization despite natural drift, achieving both reduced complexity and maintained precision through adaptive control.
Data Source
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AI summary
A second media rendering device in a network is synchronized with a first media rendering device in the network. At a first time s1, the second media rendering device sends a request for a current audio sample index from the first media rendering device. The first media rendering device receives the request for the current audio sample index from the second media rendering device. The first media rendering device sends a message including a first current audio sample index equal to a value for a first media rendering device internal sample index. At a second time s2 the second media rendering device receives the first current sample index value from the first media rendering device. The second media rendering device determines a transmission latency, and estimates an updated first media rendering device internal sample index value.