So I got a new docking station for my work laptop.
On my desk, I have 3 monitors, all of which are
best at 4k@60hz. This is a lot of pixels to push
from a laptop, especially over a USB-C (the laptop
in question has no other video output options).
Anyway, after a bit of searching, I found a
docking station which claims to output 3x4k@60,
but it does so in a novel configuration (for me at
least).
When one or two displays are connected, both
function as regular old DisplayPort displays.
Nothing clever, and they work just fine at the
native resolution. However, when you connect a
third display, then something interesting happens.
The first two DisplayPorts pair into a single
'virtual output', powered by a technology called
DisplayLink, and the third port becomes a standard
DisplayPort passthrough.
I hadn't heard of DisplayLink before; it appears
to be a proprietary standard (yes, they support
open-source operating systems, but it seems to be
'support' as in 'here's a binary blob which we
only tested with Ubuntu') which involves creating
a virtual graphics card which spans the display
output, and then encoding and decoding the signal
as it travels down the USB-C cable between the
laptop and the docking station. I understand why
this is done, USB-C only has limited bandwidth,
but it works surprisingly well. I don't detect any
percetible lag (though I'm not super sensitive to
this anyway), and I've only seen very limited
colour banding as a compression artifact under
certain circumstances. I'm honestly very
impressed; it's a clever solution, and it seems to
be well implemented. Are they really compressing
and decompressing a video delta in under 16ms? Or
is there some other trickery here which I don't
understand.
