How can I wirelessly transmit 1080p@60fps with short latency? That was one of my biggest questions. Most FPV systems are analog, which results in a bad image. That’s why I wanted to have a digital solution. First I thought of using Wifi, but soon I realized that it would have too much latency. Some people reported having over 150ms. After advices of Oculus VR the motion-to-photons latency (time from moving head to the matching image) should be under 20ms. So Wifi wasn’t an option. Perhaps it would be possible to get the latency down with a lot optimizations, but I didn’t have the time for that.
After searching for a while, I found the standard Wireless HDMI. Most of the systems work on 5.1 – 5.8 GHz. I decided to take the Nyrius Aries Pro, because it promised reasonable range (~40 meters) with <1ms latency. In addition the transmitter can be powered over USB. Because the transceiver acts like an HDMI cable, it also transmits audio. The downside is that the final image has directly to be transmitted to the Rift, so the video procession part has to be done on the robot.
In order to not only move the vision to another place, I added a microphone to the onboard computer. This sends the input to the HDMI output. To get the audio to some headphones, I put an HDMI splitter between the receiver and the Rift. The HDMI splitter was then connected to a Samsung TV, into which the headphones were plugged. In addition, the public could also see what the Rift-wearer sees.
I am quite happy with Nyrius Aries Pro; it has a feasible range to cruise in the office. But for an immersive telepresence robot, it will be necessary to find a solution for transmitting the video stream over the internet.
The next article will cover the processing the live video of the stereo cam for the Oculus Rift and audio of the microphone.
If you have any suggestions or questions, please use the comment form. I am always happy to learn something new.
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