In Mixed Reality (MR), users rely on real-time video streams through the camera passthrough feature to merge their real-world environment with the digital one. This allows for seamless interaction between virtual and physical spaces, offering a more immersive and practical experience for everything from gaming and design to training and work applications.
However, one of the most frustrating issues that users face is camera passthrough lag, where the video feed from the cameras doesn’t display in real time. This lag can break immersion, reduce usability, and potentially make the system feel disorienting or even unsafe, especially in dynamic environments.
In this article, we will explore the causes of camera passthrough lag in MR headsets, the impact on user experience, and potential solutions to mitigate this issue.
What is Camera Passthrough in MR Headsets?
Camera passthrough refers to the ability of MR headsets to use external cameras to display the real world in real-time, usually rendered into the virtual environment. This allows users to see their surroundings without having to remove the headset, blending virtual elements with physical objects in a mixed-reality space.
Commonly used features involving camera passthrough include:
- Room-scale tracking (seeing your environment while interacting with virtual objects)
- Object detection for interactions with physical objects while immersed
- Safety boundaries (boundary lines shown when users approach the limits of their play area)
- Augmented reality overlays like virtual notes or markers placed in the real world
What is Passthrough Lag?
Passthrough lag refers to the delay between the real-world actions of the user (e.g., moving their head or hand) and the corresponding video feed shown through the headset. This lag can result in a delay in visual feedback, making it harder to align virtual elements with real objects, and making users feel disoriented.
For example, when a user moves their head, there might be a fractional delay in seeing that movement reflected in the passthrough video feed. This delay can cause:
- Ghosting of virtual objects
- Disorientation in physical navigation
- Difficulty interacting with real-world objects while immersed
Causes of Camera Passthrough Lag in MR Headsets
✅ 1. Camera Frame Rate Limitations
- MR headsets typically rely on external cameras to capture the environment in real-time. These cameras often have lower frame rates than the display inside the headset, which can cause a noticeable delay in transmitting the feed.
- For instance, a camera capturing the environment at 30–60 FPS can introduce lag when paired with a headset running at higher refresh rates (e.g., 90–120 Hz).
✅ 2. Processing Power and Latency
- The processing power of the headset itself plays a crucial role in handling passthrough video feeds. If the GPU or CPU is overloaded with other tasks, such as rendering virtual objects, there may be a noticeable delay in processing the camera feed.
- Compression algorithms are often used to reduce the data load from the cameras, but this can introduce delays in decompression and rendering the video stream.
✅ 3. Sensor Fusion Delays
- Sensor fusion is the process of combining data from multiple sensors (e.g., cameras, accelerometers, gyros) to map the environment and track user movement.
- If the system takes too long to fuse the data from the cameras and other sensors, the result is a noticeable lag between real-world motion and visual feedback on the passthrough.
✅ 4. Network Latency in Wireless Devices
- For wireless MR headsets, network latency can be a factor, especially when using cloud computing for processing or streaming content. Any delay in the data transfer between the headset and the processing unit (e.g., PC or cloud server) can cause lag in the passthrough video feed.
✅ 5. Display Latency
- Even if the passthrough video feed is rendered without significant delay, there may still be issues with the display refresh rate. If the passthrough video isn’t synchronized properly with the internal display’s refresh rate, this can introduce a mismatch in the timing of visual feedback, causing a lag.
✅ 6. Software and Driver Issues
- Sometimes, passthrough lag can be attributed to software issues, including outdated firmware, drivers, or bugs in the MR platform or SDK. If the software isn’t optimized for smooth passthrough, this can significantly increase latency.
The Impact of Passthrough Lag on MR User Experience
Passthrough lag can drastically affect several aspects of the MR experience:
✅ 1. Disorientation and Motion Sickness
- Delayed feedback between physical and virtual movements can cause disorientation and motion sickness. This is especially true for users who rely on passthrough for navigation in a room-scale environment, where precise spatial awareness is critical.
- This can lead to nausea and a general sense of unease, diminishing the overall experience.
✅ 2. Difficulty in Interacting with Real-World Objects
- Many MR experiences involve interacting with both physical and virtual objects at the same time. If there’s a lag in the passthrough feed, it can become difficult to accurately position virtual objects relative to physical ones.
- In applications like training simulations or remote collaboration, even a slight lag can impair performance or cause errors in tasks.
✅ 3. Frustration and Reduced Productivity
- For professional applications such as design, engineering, or remote assistance, the user may need precise alignment of digital content with physical objects. Passthrough lag can interfere with this, reducing productivity and increasing frustration.
How to Fix or Minimize Camera Passthrough Lag
✅ 1. Increase Camera Frame Rates
- Manufacturers can improve camera performance by opting for cameras with higher frame rates (e.g., 90 FPS or more), which would result in a smoother passthrough experience. Alternatively, improving the software that processes the video feed could help reduce the lag.
✅ 2. Enhance Processing Power
- Upgrading the GPU or CPU in the headset to handle more intensive processing tasks could reduce lag. Headsets with dedicated processing units for camera passthrough (like the Valve Index or Meta Quest Pro) can help reduce this problem.
✅ 3. Optimize Sensor Fusion
- Improving the synchronization of sensors can reduce delays in tracking and data fusion. Hardware and software improvements that allow for more efficient sensor data fusion can reduce the time it takes to translate real-world movements into digital representation.
✅ 4. Use Wired Connections for Lower Latency
- For wireless MR headsets, using a wired connection or improving Wi-Fi performance can reduce network-induced latency. A high-speed USB-C connection or direct connection to a PC can lower the time it takes for data to be processed and transmitted.
✅ 5. Reduce Compression
- Minimizing the compression of the camera feed or improving the compression-decompression algorithm can reduce latency in video transmission. This would allow for smoother passthrough with reduced delay in the feed.
✅ 6. Regular Software and Firmware Updates
- Ensuring that the headset’s firmware, drivers, and software are up-to-date is crucial for maintaining optimal performance and reducing any lag issues. Regular updates often include performance improvements and bug fixes for camera passthrough.
Future of Camera Passthrough in MR Headsets
As MR technology continues to evolve, it is likely that we will see improvements in several areas that help address passthrough lag:
- Higher-resolution cameras and faster frame rates
- Better sensor synchronization for smoother fusion of real and virtual data
- Active cooling systems to improve hardware performance
- New algorithms for low-latency image processing and transmission
With these advances, we can expect the passthrough experience to become much more fluid and responsive, contributing to a more immersive and practical MR experience.