Raspberry Pi Adds Second HDMI Port to Laptop
Pierre Couy used a Raspberry Pi to give his laptop a second HDMI port.
Multi-monitor setups are practically a necessity for those of us who do Serious Work™ with our computers. In my case, that work is usually writing. But even that benefits from my dual-monitor setup, as it lets me use one screen for my word processor and the other screen for my research in a browser. Pierre Couy is a software developer who also likes to use two monitors, but he made the mistake of purchasing a laptop that only had a single HDMI port. To solve this problem, he used a Raspberry Pi to give his laptop a second HDMI port.
Like most modern laptops, the model Couy purchased does have an HDMI port. But Couy didn't want to use the laptop's built-in screen — he wanted to use two external monitors. His previous laptop supported Display Port over USB-C in addition to the HDMI port, so connecting two external monitors wasn't a problem. The new laptop, however, didn't have the Display Port support. That meant that Couy could only use the laptop's screen and a single external monitor. Luckily, he was able to find a solution in the form a Raspberry Pi single-board computer that streams another desktop feed to a second external monitor.
Couy's initial solution was what most of us would have tried: he installed a VNC server on the laptop and an VNC client on the Raspberry Pi 3 Model B. But that stretched the Pi's processing power a bit too much, as it required a full desktop environment with the VNC client running in a window. VNC is also notoriously laggy.
That led to Couy to a custom solution, which uses ffmpeg running on the laptop to stream a video feed of an X server virtual desktop to the Raspberry Pi running ffplay. That's an oversimplification, as Couy had to do quite a lot of tweaking to get the right configuration for a smooth stream. The stream travels via Ethernet connections, which allows for high bandwidth. But Couy still had to reduce the frame rate to keep the latency down and the stream smooth.
As Couy notes in his write-up, there are other solutions. But this is a simple way to take advantage of standard Linux utilities and an affordable Raspberry Pi to add an external monitor.