Multi-Device Audio Synchronization with Out-of-Band Clock Timing
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Solution Overview
Problem
Existing networked media playback systems face challenges in synchronizing audio playback among 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 synchronization signaling by transmitting clock timing via two or more communications links, including a first and second communications link using different protocols, such as a WLAN link and an optical, radio frequency, or audio link, to enhance clock synchronization and synchronous playback accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clock timing is transmitted over a single network connection, then the system complexity is low, but the synchronization reliability degrades under network congestion
Solution Approach 1:
The patent segments the clock timing transmission by using multiple separate communication links (e.g., WLAN and Bluetooth) instead of relying on a single network connection. This segmentation allows the system to maintain synchronization reliability even if one link experiences congestion or failure, as the clock timing can be received through alternative paths.
Solution Approach 2:
The patent introduces an intermediary mechanism by using a second communication link as a backup or alternative path for clock timing transmission. This intermediary link acts as a mediator that can provide timing information when the primary link is compromised, thereby improving overall synchronization reliability.
2Reliability
If multiple communication links are used for clock timing transmission, then the synchronization reliability improves, but the device complexity increases
Solution Approach 1:
The playback device autonomously manages the multiple communication links by automatically selecting which link to use for receiving clock timing based on current network conditions. This self-service approach eliminates the need for complex external coordination or manual configuration, as the device independently handles link selection and switching to maintain synchronization.
Solution Approach 2:
The system dynamically changes operational parameters by switching between different communication links based on network conditions. The playback device monitors the quality and availability of each link and adjusts its timing reception strategy accordingly, changing which link is active for clock synchronization at any given moment.
3Measurement precision
If clock timing is transmitted over congested network links, then the system simplicity is maintained, but the synchronization precision degrades
Solution Approach 1:
The patent segments the timing transmission path by utilizing multiple separate communication protocols and links (WLAN, Bluetooth, optical, RF, audio). This segmentation ensures that clock timing information can traverse different physical and logical paths, avoiding congestion on any single network and thereby maintaining high synchronization precision.
Solution Approach 2:
The patent substitutes traditional single-network mechanical communication with a multi-protocol communication system. By replacing reliance on a single network infrastructure with diverse communication mechanisms (wireless, wired, optical, acoustic), the system achieves higher timing precision without being constrained by the limitations of any single communication medium.
Data Source
Figure 1A
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 off set/ error comprises estimating and/or calculating the clock time and/or clock time off set/ 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.