Client-Server VSYNC Synchronization for Stable Cloud Gaming Latency
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Solution Overview
Problem
Existing cloud gaming systems face high latency due to differences in clock frequencies between cloud gaming servers and clients, leading to latency instability and variability in video frame synchronization.
Innovation Solution
Synchronize and offset VSYNC signals between the cloud gaming server and client to align their frequencies and adjust timing offsets, allowing for reduced one-way latency by aligning video frame generation and display times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VSYNC signals are not synchronized between server and client, then clock frequency differences cause latency instability, but synchronizing VSYNC signals requires complex timing adjustment mechanisms
Solution Approach 1:
The system measures the actual arrival time of video frames at the client and uses this feedback to dynamically adjust the VSYNC signal timing at the server. This closed-loop feedback mechanism ensures latency stability while automatically compensating for network variations without requiring complex manual timing adjustments.
Solution Approach 2:
The system performs preliminary timing measurements during an initialization phase to determine the baseline transmission time between server and client. This preliminary action establishes reference values that are used to synchronize VSYNC signals before actual gaming begins, reducing the complexity of real-time timing adjustments.
2Loss of time
If video frames are transmitted with strict timing synchronization, then one-way latency is reduced, but network variability causes frame delivery failures
Solution Approach 1:
The system dynamically adjusts the VSYNC timing based on current network conditions rather than using fixed timing. When network variability is detected, the system flexibly modifies frame transmission timing to maintain both low latency and reliable delivery, allowing it to adapt to changing network conditions in real-time.
Solution Approach 2:
The system changes the timing parameters of VSYNC signals based on measured network conditions. By adjusting parameters such as frame transmission intervals and synchronization offsets in response to network variability, the system maintains optimal latency while ensuring reliable frame delivery under varying network conditions.
3Productivity
If VSYNC frequency is increased to improve frame rate, then video quality improves, but latency variability increases due to clock frequency differences
Solution Approach 1:
The system continuously monitors the actual timing of frame delivery at high frame rates and uses this feedback to adjust VSYNC synchronization. This ensures that even at increased frame rates, latency remains consistent by dynamically compensating for clock frequency differences between server and client.
Solution Approach 2:
The system performs preliminary synchronization calibration before high-frame-rate gaming begins, establishing accurate timing references that account for clock frequency differences. This preliminary action enables the system to maintain latency consistency even when operating at higher frame rates during actual gaming.
Data Source
AI summary
A method is disclosed including setting, at a server, a server VSYNC signal to a server VSYNC frequency. The server VSYNC signal corresponding to generation of video frames during frame periods for the server VSYNC frequency. The method including setting, at a client, a client VSYNC signal to a client VSYNC frequency. The method including sending compressed video frames from the server to the client over a network using the server VSYNC signal, wherein the compressed video frames are based on the generated video frames. The method including decoding and displaying, at the client, the compressed video frames. The method including analyzing the timing of one or more client operations to adjust the relative timing between the server VSYNC signal and the client VSYNC signal, as the client receives the compressed video frames.