Keeping projector order: some tested results

Fred

There have been quite a few posts over the years about projectors getting re-ordered on reboot. I thought I would report a few working scenarios. Some of these are already documented in this forum, but I thought I would gather them here.

The main issue causing this problem is that a computer needs all the display devices connected and turned on to recreate a display configuration. Any missing outputs can cause the displays to re-order. This can happen if the display devices are connected or turned on in a different order.

Also, displays are identified by transmitting their EDID profile through the HDMI to the output device. This contains information about the display's capabilities and current settings. It should also contain the device's serial number, allowing the computer to see a display as unique, even if it has the same brand and model as another. These unique serial numbers is what allows the computer to put the displays in the order you want even after rebooting.

Issues

When a computer is on without displays connected or powered, and they are turned on or connected, they will connect to the computer one by one. As each is found, depending on the OS, a new display configuration is created, which may or may not be what you want. This is a major source of displays re-ordering.
Some displays or devices in your chain (such as signal extenders, EDID emulators, GPUs, drivers, or operating systems) will not pass the serial numbers. Consequently, the display setup does not see the outputs as unique and will re-order them as best it can, but this can be reflective of whatever is detected first.

Solution 1 - Cheap but risky

Connect and configure your display devices one by one as you setup our system, before doing your stage setup, before launching Isadora at all. This is best done in the order they appear. For example, let's imagine a setup with a control screen and a three-way horizontal blend. Connect the control screen ONLY first – you will likely have this setup already so you can actually use the computer (do this without Isadora or whatever software you are using to span the screens). Then connect the leftmost screen, set it to the correct resolution and refresh rate, connect the second screen, set it to the correct resolution and refresh rate, and then do the same for the third screen.

This works best if you don't have to re-order the displays with the OS to get them in the correct positions. Connect them in a logical order so you can move your mouse from the leftmost screen to the rightmost screen without needing to re-order the displays with the OS. As you add each screen, they should appear to the right of the existing screens, so do them left, centre then right.

To make things easier, create a still image with the screen ID and set it as your desktop background for each screen. This should help if things go wrong. Without your media software running and with the screens on, they should display the desktop background in a logical order. In our scenario, the control screen will say "control," and each projector, left to right, will say "1," "2," and "3" respectively. Once you are done, rejoice in being organised and admire this simple stage of the setup.

Now open Isadora (or whatever you are using) and configure your software outputs (stages).

To minimise the risk of things going wrong, never power off or disconnect any displays, display extension systems, or other devices that sit between the computer outputs and the display while the computer is on - NEVER. If you need to turn off the projectors, turn the computer completely off first. Never turn the computer on until all devices in the display chain are connected and completely on.

This is not 100% reliable, but it can minimize display re-ordering and likely get rid of 90+% of issues.

Options: For OSX, there is an application called Better Display that can further control issues by creating virtual screens and associating these with output devices by serial number. This works well but uses a fair amount of resources to create the virtual displays. SwitchResX can also help a lot (again for OSX). It will reveal display modes that your OS might hide and store multi- display presets that should take over the OS display settings.

Solution 2 - Not Free, but Simple and Very Effective

EDID emulators are little inline devices that will make your computer think that it always has displays connected, even if parts of that chain are powered off or disconnected. The simplest way to use them (and for our scenario, most reliable) is to use the devices to clone an existing EDID profile. As above, connect the displays one by one (again with Isadora or any other software used to feed your displays off). Once a display is connected and the resolution is correct, unplug the HDMI, plug in the EDID emulator, then plug the display chain into the emulator and let it clone the EDID. This will clone all information (on a decent emulator), including the serial number. Repeat the process for all displays, and as you add each one, confirm the settings and display order.

Although you can connect the emulators anywhere along the HDMI chain, do this as close to the computer as possible. Plug them into the HDMI output or the Thunderbolt/USB-C to HDMI dongle. As EDID emulators need to be capable of the display resolution and refresh rate they pass through, make sure you get an appropriate one. I have been using Lindy models – here is one that supports 4K60p at 4:4:4 (so 18GHz).

This method means you can turn off and on any projectors or other devices in the display chain, and the computer will see all the displays as connected. If you need to change resolutions, projectors, extension systems, or display orders, it is best to do the connection one by one again from the start.

This should take care of 99% of any issues. Most importantly, you can turn displays and the computer on and off independently.

Solution 3 - Not Free, a Bit More Complicated and Very Effective

Sometimes issues may still happen. In my experience, this is due to serial numbers not being injected into the EDID profile by the display manufacturer or being ignored by the GPU, OS, or other devices in your chain, like HDMI extension systems. To fix this, the best method is to create a custom EDID profile and then use EDID emulators to clone that (as cloning the generic profile will keep it exactly as is).

To edit and inject the EDID reliably, you need hardware that can read the EDID from the HDMI and has a way of downloading and uploading the captured and edited profile. Two devices that can do this are:

Both these devices can work similarly to the small dongles. You make a connection and confirm all settings are correct. Unplug the display, put the EDID editor inline, and capture the EDID. Let the captured EDID take over and confirm it is correct. Then, using the software provided by the manufacturer, transfer the captured EDID to your computer and edit it – make sure you don't edit anything but the name (there are several places this can be done, and it is in the timing section that is important). Make the name something like "wallBlend1" or anything unique and descriptive. NB, the kramer software will not let you edit the name, but you can export the profile and use Analogue Way's EDID editor to change it, save it, open it up in the kramer software and continue) Transfer the edited EDID back to the device and set it as the active EDID. Connect the device and your display, and make sure it works – the name of the display should now be whatever you edited it to. If this is all working you can now add the EDID emulator before the EDID editing device and the display, and clone the EDID on the emulator as in the previous method. Now you can remove the editor and plug the display back in. Repeat, giving unique names for each display.

This method is pretty bulletproof. It does require an EDID editor, but following these instructions, you only need one and you use the simpler emulators to store and utilise the editied profiles instead of needing a lot of these more expensive devices

Addendum: Complex EDID Issues

Blackmagic and other capture devices can be difficult to deal with as they output a full EDID with a whole range of options. but only really accept a single format at a time. Even when you select a format, say 4K50p, the EDID they emit will still have all the options (even though technically speaking, they should switch to an EDID that only contains a match for the format). This is further complicated when anything else is inline – say a fiber converter or HDBaseT system. For this scenario we will imagine an on stage HDMI input that goes to a far away computer capture card, using a less than amazing fibre extension system - like this one that is only AUD$600 (some very expensive fibre, or other extension gear may deal with this a little better).

When you have a connection like this – a computer feeding a capture card with a fiber extension system in between – several negotiations need to take place but will often happen out of order. Let's say you connect all this stuff, and your computer that you want to capture outputs 1080p50 by default when connected, but you want to send 4K50p. Your fiber transmitter has negotiated the EDID with the laptop, then negotiated its own connection from transmitter to receiver, and then the receiver negotiates the EDID again with the Blackmagic device. When you change the format being output by your computer, because the EDID on the Blackmagic device has many options, the fibre receiver will not see a need to renegotiate the handshake. You will likely have to do the whole setup and not see a picture on the input. To force the EDID handshake between the fibre receiver you will need to unplug the receiver from the Blackmagic device and plug it back in. This will force the EDID handshake between the receiver and the Blackmagic device, and your picture should come through.

To fix these issues, the best way is to use the presets on an EDID emulator. As there is no display configuration like on a computer, there is no need to care about names or serial numbers for unique display IDs – you only care about the format. Set the EDID emulator to the format you want (the lindy model I linked to has a number of presets), plug it into the output of the fiber receiver, connect your computer to the input of the fiber transmitter, and it should only see the format you need. Then connect the output of the EDID emulator to the input of the capture device and then set the capture device to the same format as the EDID emulator. Removing the EDID options seen by the computer and limiting to a single format will remove the need for the last EDID handshake (that is often done out of order) and let you get a clear image pathway.

This advice is from real setups, and these configs have been useful for problem solving for me in the past and have let me have reliable setups with no need for dealing with display order. Having said that hardware, software and technology will change. These are based on the fundamental way EDID works in controlling display connections and should hold true even if specific devices and capabilities change.

Happy video stuff- Fred.

DillTheKraut

thank you @fred,

this is a very extensive how to.

I might add one other option, which might foremost be good to know when someone has to decide on PC Hardware or have older professional GPUs
AMD and NVIDIA offer special professional grade GPUs.
NVIDIA:
till around 2020 called quadro
now all RTX with a plane 00 at their last name digits (RTX 6000, 5000, 5500, 4000, 4500, 800)

AMD:
old ones till 2016 AMD FirePro
now just Radeon Pro

This workstation GPUs have an internal EDID managment which is replacing the need of external devices like EDID manager / emulator.
If this feature is activated in the GPU drivers settings, this settings override any EDID handshakes from external devices and ignoring any reconnections.
On top of this, EDID informations read from the external devices can be saved to a file and loaded permanently to the Outputs where needed.

This GPUs are meant for professional workstation, and are much more expensive then their 'gaming' equivalents.
But they often offer more outputs and might be optimized for video en-/decoding. All in all especially the quadro cards are said to be more reliable.

mark_m

@fred said:

As EDID emulators need to be capable of the display resolution and refresh rate they pass through, make sure you get an appropriate one. I have been using Lindy models – here is one that supports 4K60p at 4:4:4 (so 18GHz).

Thank you so much, @Fred, for this excellent post.

I can also recommend this low-cost ATEN EDID emulator, which works with my non-standard 1400 x 1050 SXGA+ projectors. I use four of them on the MiniPC in my signature and they work very well at keeping the screen order consistent in Isadora.

bonemap

@fred

Brilliant! Thanks for sharing

Best wishes

Russell

Juriaan

@fred

Thanks Fred for this resource :)

jfg

Thanks a lot Fred.

Best regards,

Jean-François