Blur Busters Forums

<Technical>

For a display engineer, it is theoretically easy to manufacture an adaptor to convert DisplayPort FreeSync to HDMI VRR.

The VRR timings protocol is identical (nearly all VRR technologies simply use a dynamically-variable Vertical Back Porch, that's all variable refresh rate is). The blanking interval varies in size, in realtime between pairs of adjacent refresh cycles, to temporally space asynchronous refresh cycles apart, and you can do pretty much a straight 1:1 dotclock conversion between FreeSync, VESA-Adaptive Sync, or HDMI 2.1 VRR .... They're all binary interoperable with each other!

The main problem is identification.... EDID and DisplayID.... That's where the programming & software effort gets complicated. Graphics drivers often refuse to output VRR to a display that doesn't properly advertise their sync technology. ToastyX CRU can force FreeSync to an HDMI output on a Radeon product but not an NVIDIA product. So it can be done.

It's just a pesky "identification" problem. Crack that successfully and it's easy to adaptor DisplayPort VRR into HDMI VRR.

</Technical>

Chief Blur Buster wrote:<Technical>

For a display engineer, it is theoretically easy to manufacture an adaptor to convert DisplayPort FreeSync to HDMI VRR.

The VRR timings protocol is identical (nearly all VRR technologies simply use a dynamically-variable Vertical Back Porch, that's all variable refresh rate is). The blanking interval varies in size, in realtime between pairs of adjacent refresh cycles, to temporally space asynchronous refresh cycles apart, and you can do pretty much a straight 1:1 dotclock conversion between FreeSync, VESA-Adaptive Sync, or HDMI 2.1 VRR .... They're all binary interoperable with each other!

The main problem is identification.... EDID and DisplayID.... That's where the programming & software effort gets complicated. Graphics drivers often refuse to output VRR to a display that doesn't properly advertise their sync technology. ToastyX CRU can force FreeSync to an HDMI output on a Radeon product but not an NVIDIA product. So it can be done.

It's just a pesky "identification" problem. Crack that successfully and it's easy to adaptor DisplayPort VRR into HDMI VRR.

</Technical>

A guy on reddit theorized that a display port 1.4 to hdmi 2.1 adapter that currently doesn't exist could possibly do the trick. Unfortunately there isn't an adapter out there that will allow this. I tried the club 3d adapter to get freesync working and no dice.

tygeezy wrote:A guy on reddit theorized that a display port 1.4 to hdmi 2.1 adapter that currently doesn't exist could possibly do the trick. Unfortunately there isn't an adapter out there that will allow this. I tried the club 3d adapter to get freesync working and no dice.

Theory? Hah!

Reality: You don't need HDMI 2.1. Variable refresh rate works on older HDMI specs.0

It's an identification problem not a video signal problem. Basically EDID or DisplayID, where a display tells the computer whether or not it supports variable refresh rate. That IS the problem.

We got FreeSync working as old as HDMI 1.4 through the ToastyX CRU hack to do an EDID override (the FreeSync identification added to the EDID).

Even an "DisplayPort 1.4 to HDMI 2.1" adaptor WILL NOT WORK for variable refresh rate IF it doesn't properly convert the identification signalling properly (e.g. DisplayID <-> EDID conversion including the FreeSync advertising).

You could do it via a theoretical EDID-overriding adaptor rather than a DisplayPort-to-HDMI adaptor. Two adaptors in series. GPU -> DIsplayPort -> Generic old DisplayPort-to-HDMI adaptor that removes FreeSync ID -> EDID-overriding adaptor that re-adds FreeSync ID -> HDMI device supporting FreeSync).

Ideally, I'd prefer identification conversion, rather than identification removal and readd, because it would potentially preserve range advertising (the identification, EDID and DisplayID) advertises the FreeSync range, so it doesn't have to be manually configured into an EDID-override.

So any engineer wants to take upon this? Or an existing adaptor vendor (even DisplayPort 1.3 to HDMI 1.4) to fix the identification-conversion to preserve the communications of the FreeSync range maybe?

Reality. Not theory.

Chief Blur Buster wrote:

tygeezy wrote:A guy on reddit theorized that a display port 1.4 to hdmi 2.1 adapter that currently doesn't exist could possibly do the trick. Unfortunately there isn't an adapter out there that will allow this. I tried the club 3d adapter to get freesync working and no dice.

Theory? Hah!

Reality: You don't need HDMI 2.1. Variable refresh rate works on older HDMI specs.0

It's an identification problem not a video signal problem. Basically EDID or DisplayID, where a display tells the computer whether or not it supports variable refresh rate. That IS the problem.

We got FreeSync working as old as HDMI 1.4 through the ToastyX CRU hack to do an EDID override (the FreeSync identification added to the EDID).

Even an "DisplayPort 1.4 to HDMI 2.1" adaptor WILL NOT WORK for variable refresh rate IF it doesn't properly convert the identification signalling properly (e.g. DisplayID <-> EDID conversion including the FreeSync advertising).

You could do it via a theoretical EDID-overriding adaptor rather than a DisplayPort-to-HDMI adaptor. Two adaptors in series. GPU -> DIsplayPort -> Generic old DisplayPort-to-HDMI adaptor that removes FreeSync ID -> EDID-overriding adaptor that re-adds FreeSync ID -> HDMI device supporting FreeSync).

Ideally, I'd prefer identification conversion, rather than identification removal and readd, because it would potentially preserve range advertising (the identification, EDID and DisplayID) advertises the FreeSync range, so it doesn't have to be manually configured into an EDID-override.

So any engineer wants to take upon this? Or an existing adaptor vendor (even DisplayPort 1.3 to HDMI 1.4) to fix the identification-conversion to preserve the communications of the FreeSync range maybe?

Reality. Not theory.

Wow great info! Thank you!

Is there any update or progress on getting freesync over HDMI to work on nvidia GPUs?

I have a PC in the living room that is connected to a TV, but would like adaptive sync to work. Unfortunately Gsync TVs are too expensive and freesync TVs do not have displayport. When I get a new TV with freesync, I am tempted to switch to an AMD GPU. However, it would be great if I can still use my nvidia GPU.