Adaptive Screen Capture Rate for Bandwidth Congestion
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Solution Overview
Problem
Current remote computing systems face challenges in managing network bandwidth efficiently, leading to issues such as dropped frames and poor user experience due to congestion, especially as server scalability increases.
Innovation Solution
The system adjusts the capture rate of graphics data based on downstream conditions, setting it to approximately 30 captures per second for small screen updates and decreasing or increasing it according to available bandwidth, while ensuring gradual changes to avoid jerky images, and supports multiple monitor solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If every captured frame is compressed and transmitted at a high rate, then the user experience improves with lower latency and smoother updates, but network bandwidth is exceeded causing congestion and dropped frames
Solution Approach 1:
The system dynamically adjusts the capture rate based on downstream bandwidth conditions. When bandwidth is abundant, the capture rate increases to provide smoother updates. When bandwidth becomes congested, the capture rate decreases to prevent frame drops. This dynamic adjustment resolves the contradiction by making the system adaptable to changing network conditions rather than operating at a fixed rate.
Solution Approach 2:
The system monitors downstream bandwidth conditions and uses this feedback to adjust the capture rate. By continuously observing network capacity and adapting the frame capture frequency accordingly, the system ensures reliable frame delivery without consistently exceeding bandwidth limits, thus resolving the contradiction between reliability and resource consumption.
2Speed
If the capture rate is increased to reduce latency and improve responsiveness, then user interaction experience improves, but network congestion worsens leading to dropped frames
Solution Approach 1:
The capture rate is made dynamic rather than static. The system can increase the capture rate when bandwidth is available to reduce latency and improve responsiveness. When congestion is detected, the rate is decreased to prevent frame drops. This dynamic behavior resolves the contradiction by allowing high speed only when reliability can be maintained.
3Loss of energy
If the capture rate is decreased to conserve bandwidth, then network resource usage improves, but user experience deteriorates with higher latency and choppy updates
Solution Approach 1:
Rather than using a fixed low capture rate, the system dynamically adjusts the rate based on actual bandwidth availability. This allows the system to conserve bandwidth during congested periods while maintaining high capture rates during periods of abundant bandwidth, thus preserving user experience quality without wasteful bandwidth consumption.
Solution Approach 2:
The system changes the capture rate parameter in response to bandwidth conditions. By adjusting this key parameter dynamically, the system optimizes the balance between bandwidth consumption and user experience quality, avoiding the pitfalls of both consistently high and consistently low capture rates.
4Loss of time
If screen updates are transmitted at high frequency, then latency is reduced and responsiveness improves, but network congestion increases causing frame drops
Solution Approach 1:
The system dynamically adjusts the update frequency based on network conditions. When bandwidth is plentiful, updates are transmitted at high frequency to minimize latency. When bandwidth is constrained, the update frequency is reduced to prevent congestion and frame drops. This dynamic adjustment resolves the contradiction between reducing time loss and conserving energy.
Data Source
AI summary
In various embodiments, a screen image may be divided into rectangles, and a capture component may track changed rectangles and capture the screen upon receiving an indication. For small screen updates, the capture rate may be set to ˜30 captures per second to provide a lower latency. As the screen update size increases, the capture rate may be decreased to match an allocated bandwidth. The capture rate may be increased when available bandwidth increases and decreased as bandwidth decreases. For example, the capture rate may be decreased when downstream back pressure meets predefined criteria. The capture rate change may be effected gradually to avoid jerks and jumps. Varying the capture rate by also enable audio/video synchronization with varying bandwidth variations. Some embodiments may be extended to multiple monitor solutions.