In-band Media Stream Synchronization via Marker Packets
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Solution Overview
Problem
Existing methods for synchronizing multiple real-time media streams, such as video and audio, in networks face challenges due to varying channel latencies and the complexity of using timestamps, especially in IP streams, which can lead to inaccurate synchronization and require additional signaling channels or dedicated time servers.
Innovation Solution
The method involves embedding unique marker packets into each media stream at regular intervals, using a Virtual Wall Clock (VWC) to synchronize source clocks and a destination VWC to re-synchronize streams at the receiving end, ensuring deterministic latencies and eliminating the need for additional signaling channels or dedicated time servers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If out-of-band signaling protocol is used for synchronization, then synchronization capability is provided, but additional signaling channels are required which increases system complexity and susceptibility to message loss
Solution Approach 1:
The patent combines synchronization signaling with the existing in-band media data transmission channel. Instead of using separate out-of-band signaling channels, the synchronization protocol embeds timing and synchronization information within the same data channels already used for media stream transmission, thereby eliminating the need for additional signaling infrastructure while maintaining reliable synchronization capability
Solution Approach 2:
The existing in-band data channels are made multi-functional by enabling them to carry both media data and synchronization signaling information simultaneously. This universal usage of channels eliminates the need for dedicated signaling channels, reducing system complexity while preserving synchronization reliability
2Measurement precision
If timestamps with virtual wall clocks are used for synchronization, then timing information is provided, but distributed time server infrastructure and complex clock management are required
Solution Approach 1:
The patent extracts the essential timing information functionality from complex distributed time server infrastructure and virtual wall clock mechanisms. By using simple sequence numbers and relative timing markers embedded in the data stream, it achieves precise timing measurement without requiring external time servers or complex clock synchronization protocols
Solution Approach 2:
Instead of maintaining complex, long-lived virtual wall clocks and distributed time server infrastructure, the patent uses simple, lightweight sequence numbers and timing markers that are generated and consumed locally at each endpoint. These lightweight timing objects provide sufficient precision without the overhead of sophisticated time synchronization infrastructure
3Adaptability or versatility
If IP streams with dynamic routing are used, then network flexibility is improved, but variable packet delays and path differences cause synchronization difficulties
Solution Approach 1:
The patent applies preliminary sequencing and timing marker insertion at the source before packets enter the dynamic IP network. Each packet is pre-tagged with sequence numbers and timing information, allowing the receiving end to reorder and synchronize packets even after they have traversed different network paths with variable delays, thus maintaining synchronization accuracy despite network flexibility
Solution Approach 2:
The system implements feedback mechanisms where receiving endpoints monitor packet arrival times and sequence numbers, detect desynchronization, and send control signals back to the source or intermediate nodes to adjust timing and re-synchronize streams, thereby maintaining synchronization accuracy in dynamically routed IP networks
Data Source
AI summary
Methods and systems are provided for in-band signaling of at least two simultaneous digital media streams in a network, the two simultaneous streams being a part of a media session. Each of the at least two simultaneous streams is generated from a corresponding source. The generated simultaneous streams are synchronized by using a unique marker packet. Each synchronized stream is transmitted to a destination corresponding to each source.