No HDMI Signal Detected

KVM · June 20, 2025, 7:36pm

Windows 11 with Microsoft Basic Display Adapter. I get "No HDMI Signal Detected".

The logs say:
2214.274646] lt6911c 1-002b: 0xD211 is ff
[ 2215.575983] lt6911c 1-002b: Resolution: 1024x768@61 fps (htotal=1344, vtotal=806) audio: 0 realaudio: 0
[ 2215.576038] lt6911c 1-002b: lt6911c_rcv_supported_res: unsupported resolution 1024x768@61
[ 2215.576056] m00_f_lt6911c 1-002b: lt6911c_get_timing: rcv err res, return no signal!
[ 2883.576431] lt6911c 1-002b: 0xD211 is 0
[ 2885.192367] lt6911c 1-002b: Resolution: 1024x768@61 fps (htotal=1344, vtotal=806) audio: 0 realaudio: 0
[ 2885.192423] lt6911c 1-002b: lt6911c_rcv_supported_res: unsupported resolution 1024x768@61
[ 2885.192442] m00_f_lt6911c 1-002b: lt6911c_get_timing: rcv err res, return no signal!
[ 2953.052028] lt6911c 1-002b: 0xD211 is 0

It keeps repeating the above...

I tried setting up a custom EDID code, such as this:

00 FF FF FF FF FF FF 00 06 AF 01 00 01 00 00 00
1A 13 01 03 80 1E 17 78 0A 12 C5 9E 57 47 98 27
124C 54 A5 6B 80 81 80 81 40 81 00 95 00 B3 00
D1 C0 01 01 01 01 02 3A 80 18 71 38 2D 40 58 2C
45 00 A0 5A 00 00 1E 00 00 00 FC 00 31 30 32 34
78 37 36 38 20 36 31 48 7A 0A 00 00 00 FD 00 38
3D 1E 3C 00 0A 20 20 20 20 20 20 00 00 00 FF 00
31 32 33 34 35 36 37 38 39 30 0A 20 20 20 00 88

The EDID code is accepted, but the resolution keeps showing as 1920 x 1080.

I have tried the Comet GL-RM1 on other devices with higher resolution, and it works fine. But I can't get it to work on this computer.

Firmware is V1.3.0 release1.

How can I get to work with 1024x768 resolution?

minmie · June 23, 2025, 1:25am

Because your computer attempts to output a refresh rate of 61HZ, this is regarded as an illegal refresh rate

minmie · June 23, 2025, 1:29am

00 ff ff ff ff ff ff 00 06 af 06 0f fd 00 00 00
0f 0e 01 02 80 1e 17 78 0a 12 e5 91 52 52 89 27
24 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 64 19 00 40 41 00 26 30 18 88
36 00 30 e6 10 00 00 18 00 00 00 0f 00 06 77 08
ff 01 0f 05 2e 2d ff 05 3f 01 00 00 00 fe 00 41
55 4f 0a 20 20 20 20 20 20 20 20 20 00 00 00 fe
00 42 31 35 30 58 47 30 31 56 32 0a 20 20 00 d0

try this one

austinpop · June 23, 2025, 8:01am

I have the same issue as OP, so I was excited to try this out. I pasted the above code into the cstomize field, but with no luck. I still get No HDMI on the display pane.

Log snippet:

Jun 23 07:09:37 glkvm daemon.debug kvmd: aiohttp.access INFO --- [admin (token) / 192.168.0.114] 'POST /upgrade/edid HTTP/1.0' => 200; size=290 --- referer='https://glkvm.local/'; user_agent='Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit
Jun 23 07:09:37 glkvm daemon.debug kvmd: kvmd.apps.kvmd.streamer INFO --- => -- ERROR [400.007 tid=3563] -- get 6911c resolution failed,use 1080P as default
Jun 23 07:09:37 glkvm daemon.debug kvmd: kvmd.apps.kvmd.streamer INFO --- => -- ERROR [400.007 tid=3563] -- init rv1126 encoder failed
Jun 23 07:09:37 glkvm user.err kernel: [ 400.057627] lt6911c 1-002b: 0xD211 is 0
Jun 23 07:09:38 glkvm daemon.debug kvmd: kvmd.apps.kvmd.streamer INFO --- => -- ERROR [401.007 tid=3563] -- get 6911c resolution failed,use 1080P as default
Jun 23 07:09:38 glkvm daemon.debug kvmd: kvmd.apps.kvmd.streamer INFO --- => -- ERROR [401.007 tid=3563] -- init rv1126 encoder failed
Jun 23 07:09:38 glkvm user.info kernel: [ 401.664593] lt6911c 1-002b: Resolution: 1024x768@61 fps (htotal=1344, vtotal=806) audio: 0 realaudio: 0
Jun 23 07:09:38 glkvm user.err kernel: [ 401.664648] lt6911c 1-002b: lt6911c_rcv_supported_res: unsupported resolution 1024x768@61
Jun 23 07:09:38 glkvm user.err kernel: [ 401.664666] m00_f_lt6911c 1-002b: lt6911c_get_timing: rcv err res, return no signal!

minmie · June 23, 2025, 9:16am

Does your computer not have a graphics card driver? This kind of problem with an extra frame is very strange

austinpop · June 23, 2025, 4:49pm

This is a special purpose machine, so it is what it is.

Physical monitors have no issue syncing to the output, and show the resolution at 1024x768x60Hz. See one example below:

I am not sure why the Comet is seeing an extra 61st frame. Can you create a code to ignore it and treat it as a 60Hz?

Thanks for your help so far.

mortneff · June 24, 2025, 12:14am

Guess there might be a frequency difference. Doubt it can be 61 actually.

minmie · June 24, 2025, 1:56am

The chip cannot handle input exceeding 60 frames. Even if I remove the restrictions in the kernel driver, errors will still occur in other places, such as during encoding. If I force it to 60 frames per second, either it will report errors crazily or the resulting picture will be very strange. If the problem of 61 frames output by the computer cannot be solved... This might not be solvable

austinpop · June 24, 2025, 2:42am

It would be worth trying forcing it to 60 frames.

Even if the picture is distorted, it's not like we need to do anything graphic. We really need the KVM to get to the BIOS of the machine remotely, and that is all textual anyway.

Please allow me to test it out? If it fails, then we know it's not solvable.

Do you have any idea why physical monitors are able to handle this fine?

mortneff · June 24, 2025, 2:21pm

Is this on some inverter or ups power? I still wonder about the timing issue.
Wonder if the cable is somehow crosstalking?

I'd look at power supply and cable quality if it were me.

minmie · June 25, 2025, 6:36am

I will try to build a specical firmware to you . give me some time

minmie · June 25, 2025, 8:40am

https://fw.gl-inet.com/kvm/rm1/test/glkvm-RM1-1.3.0-0625-1750840368.img
try it

austinpop · June 25, 2025, 4:52pm

It works!! Thanks for the quick turnaround. Really appreciate that. Here is what the status bar says:

And log snippet:
[ 1.823237] udevd[125]: starting eudev-3.2.7
[ 2.326077] lt6911c 1-002b: Resolution: 1024x768@61 fps (htotal=1344, vtotal=806) audio: 0 realaudio: 0

If you would like the full log, let me know. I didn't want to post it on a public forum, but can DM it to you.

Thanks again!

KVM · June 25, 2025, 5:23pm

Thank you for the quick turnaround.

minmie · June 27, 2025, 2:32am

I will add this change as a workaround on version 1.4.0, thanks for report

glman1 · July 7, 2025, 1:20am

Hi - I was also seeing the same problem, and I downloaded the new image you specified, and I can say that it also works now! I have a very constrained micro-itx NAS chassis, and limited PCIe slots, so I was forced to use this m2 HDMI adapter: https://www.asrockrack.com/general/productdetail.asp?Model=M2_VGA#Specifications -- this adapter also has the same 61fps issue. Possibly all Siliconmotion SM750 based adapters?