Tangentially related: This uses a HDMI-to-USB video capture device, which is great (I did not know they were that cheap and have ordered 2:]), but does anyone happen to know of a cheap VGA-to-USB capture device? I'm having a surprising amount of trouble turning one up, for all that I would expect them to be at least as easy to procure. (I'm interested in hacking together cheap lights out management for an assortment of oldish computers; emulating USB input devices with a microcontroller is easy, so if I could get VGA I could trivially remote control 10-15 years of computers. Unfortunately, somehow all of the "Pi LoM" projects I can find require HDMI.)
You can do composite to USB easily enough with a $10 adapter, no reason to believe VGA is fundamentally more difficult to capture. Well, not because it is analog anyway. The real difficulty is that there are ton of modes you'd have to be able to detect and support.
The HDMI to USB dongle (video encoder) usually is a wrapped MS2109 chip, you also want VGA to HDMI which is an ADC + HDMI transmitter, something like MS9282.
I guess it would be difficult to find a dongle that happen to have both chips, so the easiest way would be get a VGA to HDMI and plug it to the HDMI to USB encoder.
Why would you not just use one of the dozens of KVM-over-IP devices on the market? Or if you want to run it over a USB connection look for a "crash cart" device.
This is a solved problem space. There is no case in which you would save money by doing this, even if your time was worthless. If the PCs are old enough you'd probably want PS/2 rather than USB. For the same reason people do not build their own mobile phones.
Not OP but the KVM-over-IP devices I've seen work on multicast and thus are pretty terrible for network performance unless you have managed switches with packet inspection. They also don't play well with many WiFi access points too.
I've not seen any KVMs that work via unicast for < £100. Whereas you can easily get a HDMI capture device plus VGA to HDMI adapter for < £100.
If you know of any KVMs that don't use multicast then I'd be interested to know because I've been looking to move my CCTV display.
All the options I can immediately find seem to be hundreds of dollars and still usually need HDMI. Could you point me at a specific model or at least vendor I should be looking at?
Lantronix makes some nice products with VGA and HTML5 interface. However they seem to have tripled in price and I wonder if this is due to supply & demand. (Remember remote KVM over IP is a server-grade product that likely deals in low volumes so the price will reflect that.)
Those dirt-cheap HDMI capture cards are surprisingly useful.
How good are they with respecting content protection flags?
I've thought about getting one for a weekend project, but very occasionally my AppleTV lies to me that it can't play my own home videos because my TV doesn't support DRM. So I'm uneasy about buying a piece of gear only to find out later that it's flaky in the same way.
I would not trust them for any protected content. I have had good luck with going from a camcorder's HDMI out (using it as a fancy webcam) and output from a Raspberry Pi. Both are unencrypted signals. An AppleTV or likely even a PC's output will likely enforce encryption and I highly doubt HDMI capture will work then. But at ~$20 it's not an expensive experiment.
Yeah -- I use one to get debug console access to a Raspberry Pi, and to show the output from a Nikon or Sony camera. Not tried to see what happens with my Mac Mini, but then I only ever used that with DVI monitors, and I don't think I ever tried e.g. DVD protected content.
Mine seems to accept it and just strip it. I'm not sure the exact HDCP version it accepts but I can capture a Blu-ray from my PS3 with it which you are not normally supposed to do (it won't even play Blu-rays over component).
Among name-brand devices you will probably find they respect HDCP flags. Among random third-party devices, I am guessing that more often than not you will find they don't.
I wanted to do some capture from a PS3, as another commenter mentions they set HDCP on all output (even games) and my Elgato capture card does respect this flag. A $15 HDMI "output splitter" will strip this however, and conveniently this also means that my game does not run through the capture card (with any latency that might entail - along with having to run the capture PC even when I do not want to capture) but rather goes console -> splitter -> tv which is about as low-latency as you can get.
Note that HDCP has multiple versions - your video source might support HDCP 2.3 while your TV might only support HDCP 2.2, and that's largely fine, most content will be allowed to fall back to the older standards (which can be broken). However 4K content/etc at the highest quality levels (eg from streaming/etc) often is not allowed to be delivered at the lower quality levels - Netflix will drop the resolution if it doesn't like the DRM chain it sees (eg no SGX enclave or insufficient HDCP level) and things like a BluRay player where there's no fallback might refuse to play at all (or might similarly fall back to a 1080p downscaled output, etc).
Home videos shouldn't have HDCP flags set at all, so it's hard to say what might be happening there, but it's possible there's just some broad-spectrum "if resolution == 4K THEN require_hdcp_2.3()" type thing. I would look at the particular types of content that it's barfing on and see if there's a correlation like resolution or source device and go from there. It's a bit of a pain for sure.
Also - while HDCP 2.2 and below are thoroughly broken even by garden-variety devices at this point - HDCP 2.3 is still pretty tight. There's a few (expensive) devices that claim to do it, but it's not something you'll find in the $15 tier of "splitters". If that's the requirement, figure on paying several hundred dollars. It's gonna be easier to figure out why the Apple TV is turning on HDCP and get it to stop than to break the HDCP.
I've found good use of VGA to HDMI adapters combined with the HDMI to USB dongle. I know it's not an ideal solution, but it was the quickest and dirtiest solution I could come up with in a pinch.
Walmart[1] seems to have the VGA to HDMI adapters tucked in with the video stuff. I've also noticed they now carry the HDMI-USB adapters, branded Vivitar, for roughly $20 in the camera gear.
[1] I live in rural NY where Amazon Prime is impractical (4-5 day shipping via Prime) and my only local retail is a Walmart, so I keep an eye on what's local to me if only because if I need it ASAP...
Very cool. I was excited to try it until I saw you have to tap into the CRT cable bundle inside the Mac case. Actually, I think I'm still excited to try it — I need to recap my old Mac Plus and might as well make the hardware mod then.
(Debating whether to add a clean rear connector for the "video out" rather than the wires hanging out like in the article … it would require drilling a hole in the case.)
I'm surprised those video wires did not need to be shielded.
Flustered me would run a Mac emulator on modern hardware, capture the display that way. I know that's cheating though.
Somebody was getting rid of a Macintosh Classic that had a broken neck on the display tube. I built it in to a small tower case that was common in the early '90s and connected it to a TTL monitor using a 74LS14, which I think I learned about from the "Macintosh Repair & Upgrade Secrets" book. We used to call those Hackintoshes back then ;)
Could you get color? The original Quickdraw APIs (from 128->Plus ROMs) all had library that supported a handful of primary colors, but I was never certain if there was any hardware (pre-Mac II) that could actually do anything with color.
No, this just adjusted the video levels to TTL - and you had to adjust the frequencies of the monitor since the Hercules HSync/VSync frequencies were not exactly what the original Macs generated.
The QuickDraw source code (https://computerhistory.org/blog/macpaint-and-quickdraw-sour...) definitely has some color support, I think the CHM version source code is for an early version used in monochrome Macs (but there's no version number or date given).
29 comments
[ 1.7 ms ] story [ 106 ms ] threadi don’t think you can just do vga to usb as it’s analog to digital isn’t it?
This is a solved problem space. There is no case in which you would save money by doing this, even if your time was worthless. If the PCs are old enough you'd probably want PS/2 rather than USB. For the same reason people do not build their own mobile phones.
I've not seen any KVMs that work via unicast for < £100. Whereas you can easily get a HDMI capture device plus VGA to HDMI adapter for < £100.
If you know of any KVMs that don't use multicast then I'd be interested to know because I've been looking to move my CCTV display.
You might be able to find a used Epiphan VGA2USB for not much money.
There is a Raspberry Pi HDMI-to-CSI capture card now that presumably uses the same or similar chip:
https://www.waveshare.com/wiki/HDMI_to_CSI_Adapter
(The Pi Hut have it)
How good are they with respecting content protection flags?
I've thought about getting one for a weekend project, but very occasionally my AppleTV lies to me that it can't play my own home videos because my TV doesn't support DRM. So I'm uneasy about buying a piece of gear only to find out later that it's flaky in the same way.
I wanted to do some capture from a PS3, as another commenter mentions they set HDCP on all output (even games) and my Elgato capture card does respect this flag. A $15 HDMI "output splitter" will strip this however, and conveniently this also means that my game does not run through the capture card (with any latency that might entail - along with having to run the capture PC even when I do not want to capture) but rather goes console -> splitter -> tv which is about as low-latency as you can get.
Note that HDCP has multiple versions - your video source might support HDCP 2.3 while your TV might only support HDCP 2.2, and that's largely fine, most content will be allowed to fall back to the older standards (which can be broken). However 4K content/etc at the highest quality levels (eg from streaming/etc) often is not allowed to be delivered at the lower quality levels - Netflix will drop the resolution if it doesn't like the DRM chain it sees (eg no SGX enclave or insufficient HDCP level) and things like a BluRay player where there's no fallback might refuse to play at all (or might similarly fall back to a 1080p downscaled output, etc).
Home videos shouldn't have HDCP flags set at all, so it's hard to say what might be happening there, but it's possible there's just some broad-spectrum "if resolution == 4K THEN require_hdcp_2.3()" type thing. I would look at the particular types of content that it's barfing on and see if there's a correlation like resolution or source device and go from there. It's a bit of a pain for sure.
Also - while HDCP 2.2 and below are thoroughly broken even by garden-variety devices at this point - HDCP 2.3 is still pretty tight. There's a few (expensive) devices that claim to do it, but it's not something you'll find in the $15 tier of "splitters". If that's the requirement, figure on paying several hundred dollars. It's gonna be easier to figure out why the Apple TV is turning on HDCP and get it to stop than to break the HDCP.
https://digilent.com/reference/test-and-measurement/digital-...
Also, most logic analyzers don't work with VGA since it's an analog protocol.
Walmart[1] seems to have the VGA to HDMI adapters tucked in with the video stuff. I've also noticed they now carry the HDMI-USB adapters, branded Vivitar, for roughly $20 in the camera gear.
[1] I live in rural NY where Amazon Prime is impractical (4-5 day shipping via Prime) and my only local retail is a Walmart, so I keep an eye on what's local to me if only because if I need it ASAP...
(Debating whether to add a clean rear connector for the "video out" rather than the wires hanging out like in the article … it would require drilling a hole in the case.)
I'm surprised those video wires did not need to be shielded.
Flustered me would run a Mac emulator on modern hardware, capture the display that way. I know that's cheating though.
Building such an adapter is described on p. 168/169 in https://vintageapple.org/macbooks/pdf/Macintosh_Repair_&_Upg... and there's a thread on a projector adapter at https://tinkerdifferent.com/threads/compact-mac-video-adapte...
Great to see that this approach is still useful today!
The QuickDraw source code (https://computerhistory.org/blog/macpaint-and-quickdraw-sour...) definitely has some color support, I think the CHM version source code is for an early version used in monochrome Macs (but there's no version number or date given).