I have some older machines that I want to use with an HDMI KVM, without having to swap around audio cables as well. One is an HP t5730 Thin Client I have previously mentioned, which is a great compact system for running Windows XP, and another is a Mac mini G4, which is great for early Mac OS X apps, as well Mac OS 9 apps through the Classic Environment.
More recent machines with built-in HDMI output both the video and audio through the one connector, and the KVM then works very well in switching between sources, so I figured the best way would be to use an adapter that converts the old machines video-out to HDMI and then additionally embeds the audio-out into that.
The first I tried was the “StarTech DVI to HDMI Video Adapter with USB Power and Audio”, but there were a couple of downsides that I ran into. The first is that the output resolution becomes 1920x1080 - not sure if that’s enforced by firmware or is a technical limitation. The second annoyance is that, due to the audio running through USB, it does mean there has to be driver support for that. I couldn’t get that working under Windows XP (there may be a way if there’s a USB audio driver that allows it). Mac OS X v10.4 does support the USB audio output natively, it comes up under “System Preferences:Sound:Output” as “C-Media USB Headphone Set”.
The next option I found was a little box called the “HDMI 2.0 Audio Embedder 4K 60Hz HDMI Toslink+Analog Audio to HDMI Inserter HDR”, which didn’t seem to have specific brand-name associated with it, other than one of those seemingly randomly nonsense names.
Strangely at time of writing, it’s half the price on eBay versus what looks to be the same product on Amazon (neither are affiliate links).
What’s great about this one is it supports 1920x1200 perfectly, and as it is just taking a regular 3.5mm line-in, it is completely transparent to the machine, no drivers required.
One last tidbit, when this Audio Embedder has no HDMI input, it outputs some colour bars (pictured below) evocative of the SMPTE colour bars. Actually kind of handy just to know that it is hooked up correctly.
Currently listening: The Beatles - “Now And Then”