Elgato 4K Pro: XRGB fails to connect (ConnectPins 0x80040207), YUY2/NV12 work fine

[Ben123123]

Hi,

I'm trying to capture in RGB (XRGB) with an Elgato 4K Pro, but XRGB never gives a live picture. YUY2 and NV12 works with the exact same setup.

Log: https://obsproject.com/logs/hQkqqp4BGJ7wamNB

System
- OBS 32.2.2 (64-bit), Windows 11 Home build 26300
- HP Pavilion Gaming Desktop 790-00xx, Intel i5-9400F, NVIDIA RTX 2060
- Elgato 4K Pro (PCIe, links at Gen2 x4), driver 1.1.0.203.7, firmware 24.06.11 / MCU 25.04.16


Source settings
Video Capture Device, 1920x1080, 59.94 fps, Video Format XRGB, buffering disabled.

What happens
Every time the format is XRGB, the log shows:

format: XRGB
DShow: Elgato GC4K60ProMK2 tonemapper enable=1
DShow: HDevice::ConnectPins: failed to connect pins (0x80040207)

0x80040207 = VFW_E_NO_ACCEPTABLE_TYPES. The preview is then black or frozen on the last frame (not live). With YUY2 or NV12 the error never appears and capture works fine.

Other findings
- ffmpeg (-list_options, dshow) lists the 4K Pro's RGB formats as "unknown compression type 0xE436EB7D" and "0xE436EB7E", while YUY2/NV12/UYVY are listed normally. Those values are the first part of the MEDIASUBTYPE_RGB24/RGB32 GUIDs, so the driver seems to put them in biCompression instead of BI_RGB (0).


Questions
1. Is the ConnectPins failure caused by the driver's non-standard RGB format description (biCompression), or something on the OBS side?
2. Could the hardware tonemapper (enabled by OBS for all non-P010 formats) make RGB unavailable on the 4K Pro? Is there a way to capture XRGB without enabling the tonemapper?
3. Is there any known workaround to get true RGB 4:4:4 from this card in OBS?

Thanks!

 

[Ben123123]

Elgato support is saying it's OBS issue. Below reply from Elgato. No qualified to say if this will solve my issue but dropping it here...

"
Hello,

We heard back from our advanced support team.

It looks like this is an open bug on OBS Studio's end. There's an open ticket on their GitHub about this with another XRGB capable device here: https://github.com/obsproject/obs-studio/issues/13929

At this point, we're going to have to wait for the OBS Studio team to resolve this.

If you have any further questions, please let us know.
*NAME*
Elgato Technical Support"

 

[Ben123123]

Ran some tests with help from Claude and below results would indicate the issue is in both OBS and Elgato...:

Update: with the driver’s RGB32 media type selected and connected directly (bypassing the RGB24/RGB32 selection issue), the Elgato 4K Pro delivers frames, but they are all zeros while a live signal is present. YUY2 works. Tested with RGB, YCbCr 4:4:4 and 4:2:2 input, tonemapper on and off. So on the 4K Pro there’s also a driver/firmware issue; the OBS fix alone won’t be enough.