PTP Synchronized Video Transmitters for Seamless Switching
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Solution Overview
Problem
Existing video transmission systems, such as those specified in SMPTE2022-7, face challenges in making transmitters redundant for seamless video signal switching, as they lack a practical method to match RTP sequence numbers among multiple transmitters, leading to inefficiencies and overhead in high-speed video data transmission.
Innovation Solution
A video transmission system that synchronizes transmitters with a PTP grand master to independently set and manage RTP sequence numbers for IP-packets across redundant transmission paths without exchanging sequence numbers, ensuring consistent sequence numbering across all transmitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RTP sequence numbers are matched among redundant transmitters to enable seamless video switching, then video signal reliability is improved, but system complexity increases due to the need for sequence number synchronization mechanisms
Solution Approach 1:
Each transmitter independently generates RTP sequence numbers based on its own internal clock without requiring communication or synchronization with other transmitters. The transmitter uses its local system time to calculate sequence numbers, making the system self-sufficient and eliminating complex inter-transmitter coordination mechanisms.
Solution Approach 2:
The patent changes the parameter basis for sequence number generation from requiring inter-transmitter synchronization to using local system time. By basing sequence numbers on each transmitter's independent time source rather than a shared reference, the system achieves reliability without the complexity of synchronization protocols.
2Reliability
If transmitters exchange RTP sequence numbers to maintain consistency, then video switching reliability is improved, but transmission overhead increases due to additional communication protocols
Solution Approach 1:
Transmitters independently generate sequence numbers using their own system time without exchanging any information with other transmitters. This eliminates the need for communication protocols dedicated to sequence number synchronization, reducing transmission overhead while maintaining reliability through independent but consistent generation methods.
Solution Approach 2:
The patent extracts the sequence number generation function from a centralized coordination mechanism and places it locally at each transmitter. By removing the need for inter-transmitter communication for this function, the system eliminates associated overhead while maintaining the essential reliability of consistent sequence numbering.
3Device complexity
If multiple transmitters operate independently without sequence number matching, then system complexity is reduced, but video packet corruption occurs during switching
Solution Approach 1:
The patent changes the approach from centralized sequence number management to independent local generation based on system time. This parameter change allows each transmitter to operate independently (reducing complexity) while still producing consistent sequence numbers that prevent packet corruption during switching.
Solution Approach 2:
The sequence number generation function is segmented and distributed to each transmitter individually rather than being centralized. Each transmitter independently performs the generation based on its local time, eliminating the need for complex coordination while ensuring consistency through the deterministic nature of time-based generation.
Data Source
AI summary
Redundant transmitters send the same sequence numbers without matching the sequence numbers. The transmission system includes a PTP grand master, a first and second transmitters configured to synchronize a time with the PTP grand master according to PTP and receive video signals distributed from one video signal, and a receiver connected to the first and second transmitters over an IP-network, the first transmitter and the second transmitter respectively divide the video signals into a plurality of IP-packets, calculate an initial value for RTP sequence numbers based on PTP timestamps in accordance with the synchronized time according to PTP, set the RTP sequence numbers sequential from the initial value to a RTP sequence fields in the plurality of IP-packets respectively, and send the IP-packets to the receiver via a first and second transmission paths according to RTP.