IP Video Latency Stabilization Using Clock and Phase Synchronization
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Solution Overview
Problem
Conventional IP-based multimedia communication systems experience significant latency issues, leading to oscillating display latency in video transmissions over IP networks, which is problematic for applications requiring stable latency, such as remote medical procedures.
Innovation Solution
The method involves stabilizing display latency by synchronizing the frequency and phase of source and display signals using a common clock, generating correction data, and adjusting the pixel clock or blanking period to maintain non-oscillating latency, employing protocols like RTP and RTCP for timestamping and precision time protocols for network synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If IP-based multimedia communication is used, then cost of infrastructure is decreased and scalability is improved, but latency stability deteriorates
Solution Approach 1:
The system implements a feedback mechanism where the renderer measures display latency and sends latency information back to the source. The source then adjusts its frame transmission timing based on this feedback to stabilize latency. This closed-loop control enables latency stabilization over IP networks while maintaining the cost and scalability benefits of IP infrastructure.
Solution Approach 2:
The system dynamically changes transmission parameters (frame timing, transmission intervals) based on measured latency conditions. By adjusting these parameters in response to network conditions, the system maintains stable latency despite the variable nature of IP networks, while still using cost-effective IP infrastructure.
2Speed
If latency is decreased as much as possible, then speed of transmission is improved, but display latency oscillation increases
Solution Approach 1:
The renderer continuously measures display latency and provides feedback to the source. This feedback enables the source to adjust transmission timing to achieve the lowest stable latency rather than merely decreasing latency, preventing oscillations while maintaining high transmission speed.
Solution Approach 2:
Instead of the source blindly transmitting frames as fast as possible, the system inverts the control approach by having the renderer control the source's transmission timing through feedback. This reversal enables optimization for stability rather than raw speed, eliminating oscillations while maintaining efficient transmission.
3Productivity
If frame rate is increased, then productivity of video transmission is improved, but latency stability deteriorates
Solution Approach 1:
The feedback mechanism measures actual display latency for each frame and uses this information to adjust subsequent frame transmission timing. This enables the system to maintain latency stability even at high frame rates by dynamically adapting transmission timing to actual processing and display conditions.
Solution Approach 2:
The system dynamically adjusts frame transmission timing based on real-time latency measurements rather than using fixed intervals. This dynamic adaptation allows the system to maintain high frame rates while compensating for variations in processing time, ensuring latency stability despite increased productivity demands.
Data Source
AI summary
An exemplary embodiment of the present invention provides a latency stabilization system for stabilizing the display latency between a source and a renderer over an IP network. The latency stabilization system comprises a frequency syntonization module, a frequency lock detection module, and a phase correction module. The frequency syntonization module can be configured to syntonize a frequency of a source signal from the source and a frequency of a display signal to be displayed on the renderer. The frequency lock detection module can be configured to detect whether the frequency of the source signal and the frequency of the display signal are locked. The phase correction module can be configured to, synchronize a phase of the source signal and a phase of the display signal, and generate correction data based in part on synchronization of the phase of the source signal and the phase of the display signal.