Technical Challenges at Deltatest: Tackling Latency in Mobile Testing

At Deltatest, our primary goal is delivering the absolute best mobile testing experience technology can offer. A core part of achieving this experience is minimizing latency, enabling users to interact with devices remotely in real-time as though they're physically holding them.

Optimizing Capture Latency with Apple Silicon and ScreenCaptureKit

We rely on Apple Silicon machines running macOS, utilizing ScreenCaptureKit for efficient and high-performance screen capturing. ScreenCaptureKit has proven effective at consistently providing low latency capture, helping us get as close to real-time as possible.

Tackling Network Latency: UDP, WebRTC, and Beyond

Network latency, however, is inevitably constrained by physics—the speed of light itself—and by real-world network infrastructure. For example, the fastest theoretical latency between San Francisco and Dubai is approximately 240ms. Practically, network conditions often add additional delays.

UDP: Fast but Browser-Unfriendly

The absolute quickest way to transmit video streams across networks is via UDP (User Datagram Protocol), as it avoids the overhead associated with establishing and maintaining a TCP (Transmission Control Protocol) connection. Unfortunately, modern browsers don't support direct UDP communications, limiting its usefulness for web applications.

WebRTC: Potential with Challenges

The next-best option for browser-compatible low-latency streaming is WebRTC. Originally developed by Google for real-time web conferencing (such as Google Meet), WebRTC prioritizes low latency at the expense of video quality. While effective for conferencing, this trade-off poses significant challenges when precise, detailed screen viewing and interaction is required, as with mobile testing.

Our initial experiments with WebRTC didn't meet our standards. Under poor network conditions, the video stream degraded substantially, negatively impacting usability. Properly configuring WebRTC for high-quality, consistent screen sharing proved complex, and remains a task we plan to revisit. We have WebRTC-WHIP testing scheduled for further investigation later in 2025.

Notably, applications like Chrome Remote Desktop have effectively utilized WebRTC for remote desktop purposes, giving us optimism that future developments may help address our current limitations.

Media over QUIC: Promising Future Technology

Looking forward, we're particularly excited about Media over QUIC. QUIC, which powers HTTP/3, significantly reduces connection establishment overhead compared to traditional TCP. QUIC offers faster transmission times, potentially reducing latency even further.

However, this technology is still experimental. WebTransport, a key protocol for media delivery over QUIC, is currently unsupported by Safari, and robust server-side implementations are limited.

We remain closely engaged with these emerging technologies and committed to pushing the boundaries of what's achievable in mobile testing latency.