This seems a good place to ask: does anyone know of a good solution like this HDMI dummy plug, but that negotiates HDCP? I need to test video streaming apps that require HDCP to play at full resolution, but it is inconvenient to have a full TV for every test.
The one solution I've found is an HDMI multiviewer, which seems to negotiate HDCP to each port individually.
I wonder if the chips on these dummy plugs are powerful enough to hack in HDCP support though.
It terminates as an HDCP 2.0 endpoint and converts to HDCP 1.4. You’d still need an HDCP 1.4 sink to make it work though.
I found the same device in generic packaging on AliExpress, but haven't had the chance to order that version, yet.
There are lots of professional SDI converters and such, but they are either $3k+ or "call for price".
I don't agree with this section:
> The HDCP converter simply announces itself as a final video endpoint… yet still repeats the content to its output port. Without a very expensive HDMI protocol analyzer, we can’t check if the source is tagging the content as type 0 or type 1, but there is no reason now to think that it’s not type 1.
There's no magic in the HDMI protocol that says type 1 vs type 0. Its just another HDCP message over DDC, but it is only sent to repeaters. In this case, since the HDCP Repeater is lying about not being a repeater, it isn't getting sent the StreamID Type information.
>If you attempt these commands on a PC, it’s possible that you could accidentally flash hardware that isn’t an EDID, like a RAM module’s SPD EEPROM.
> At one point, Linus had implemented device files in /dev, and wanted to dial up the university computer and debug his terminal emulation code again. So he starts his terminal emulator program and tells it to use /dev/hda. That should have been /dev/ttyS1. Oops. Now his master boot record started with "ATDT" and the university modem pool phone number. I think he implemented permission checking the following day.
That would be a strange oversight by the hardware developers.
Typically they would buy pre-programmed EPPROMs and then place it on to a board where the write enable pin is never pulled high.
It would be strange to put an EEPROM into a product like a monitor and leave it writable, but I’ve seen stranger things on shipping hardware.
Tools like ddcutil aren't very well-known, but they can be quite useful if you want to do something like DIYing a KVM switch by just having the PC tell the monitor to switch to a different input!
Also, some of them have the write-protect line pulled high (or low? don't remember) and you'll need a bit of surgery to actually write to them.
I have an nice programmable EDID emulator plug, and I can clone my monitor and others, but there's some times there's a specific resolution or feature I want to set and I don't have a way to. (Like 8K with DSC, etc)
I'm aware of https://github.com/bsdhw/EDID but it's rather limited in terms of modern monitors.
I've also written by own using https://www.analogway.com/products/aw-edid-editor but getting all the nuances of various modes, and setting preference order, etc, is rather difficult, at least for me :)
Some years ago it's kind a worked for me on Linux with Xorg and open source drivers and Windows with Nvidia, but when it comes to MacOS or Windows+AMD or Intel GPU it simply doesn't work that well.
zdw•6h ago
I have a 2011 era AMD FX8350 system where the onboard 880G northbridge+video chipset doesn't output video over HDMI correctly with a 4k display. Hooking up one of these inline to tell it to send a 1080p image works great, which the monitor does a 2x integer upscale to 4k.
dougg3•6h ago
Another awesome thing is it can force the monitor to always be detected. One of my monitors virtually unplugs itself when I shut it off, which causes a bunch of issues for me, and the passthrough completely solved it. The one I use is the HD-EWB by THWT.
gadiyar•5h ago
dougg3•5h ago
I guess I should reword the way I said something in the previous message: when I said "it can force the monitor to always be detected", I really should have said "it forces the monitor to always be detected".