Out-of-Band Clock Timing for Jitter-Resistant Playback Sync
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Solution Overview
Problem
Existing networked media playback systems face challenges in synchronizing audio playback across multiple devices due to network congestion, latency, and jitter, which degrade the accuracy of clock synchronization and synchronous playback.
Innovation Solution
Implementing out-of-band clock timing signaling by using two or more communications links, including a first and second communications link with different protocols, such as WLAN and optical, radio frequency, or audio links, to transmit and receive clock timing, and employing state estimators like Kalman filters to calculate clock time and error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If clock timing is transmitted via network protocols (WLAN, etc.), then devices can be synchronized across the network, but network congestion, latency, and jitter degrade the accuracy of clock synchronization
Solution Approach 1:
The patent introduces an intermediary out-of-band communication path (separate from the primary audio/data network) to transmit clock timing signals. This mediator path bypasses the congested network infrastructure, providing a more reliable and accurate timing reference that is not subject to network latency and jitter. The intermediary path could be a dedicated hardware connection or alternative communication channel that ensures timing signal integrity.
Solution Approach 2:
The patent segments the communication paths by separating audio/data transmission from clock timing transmission. Instead of relying on a single network protocol for both functions, the system uses distinct communication channels: one for media content delivery and another dedicated path for timing synchronization. This segmentation allows each path to be optimized independently, with the timing path prioritizing accuracy and reliability over bandwidth.
2Measurement precision
If multiple communication links with different protocols are used for clock timing, then synchronization accuracy is enhanced, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by enabling playback devices to operate across multiple communication protocols and modes. A single device can function in both mesh network mode and infrastructure mode, supporting multiple protocols (WLAN, Bluetooth, optical, RF) within a unified architecture. This universality allows the system to select the most appropriate communication path based on environmental conditions while maintaining consistent synchronization performance, thereby managing complexity through standardized multi-protocol support rather than separate dedicated systems.
Data Source
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Figure 1B
Figure 1C~1E
AI summary
Disclosed embodiments include facilitating clock synchronization and/or synchronous playback among multiple playback devices in a group. An individual playback device estimates and/or calculates a clock time at a clock time source (or a time offset/error between the playback device and the clock time source) based on (i) first clock timing received from the clock time source via a primary timing link and (i) second clock timing received from the clock time source via a secondary timing link. In some embodiments, estimating and/or calculating a clock time and/or clock time offset/error comprises estimating and/or calculating the clock time and/or clock time offset/error with a state estimator, such as a Kalman filter, an extended Kalman filter, or other state estimator configured to estimate a clock time and/or clock time error based on clock timing received via two or more communications links.