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Old 04-19-2017, 11:54 PM   #1
GTM
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Default DisplayLink chip and external TV tuner

I bought a Plugable UD-3900 docking station for a new laptop, and the docking station is based on a DisplayLink chip (not sure which series). I have an external TV tuner box (AVerMedia AVerTV Box9) that I can’t get to fully work with it, and I'm trying to determine if the DisplayLink chip is the cause of the problem.

The TV tuner is a stand-alone device: it has a 75-ohm cable TV input, a video input (the video signal from the PC), and a video output (the video signal to the monitor). Because it’s a stand-alone device, it does NOT get installed in Windows, so this is definitely not a problem of compatibility with Windows 10, a driver conflict, or anything of the sort. Instead, you simply connect the video signal from the PC to its input, connect its output to a monitor, and it internally “merges” the TV video signal with the PC video signal. It allows the TV video signal to be displayed either full-screen or in a small always-on-top window that can be placed anywhere on the Windows desktop. Because the TV tuner has a VGA interface and the docking station has a DVI interface, I had to use a DVI-to-VGA adapter to connect the two. The end result is that I can view the TV video signal perfectly in full-screen mode, but when I try to view it in the small always-on-top window (which is the mode I really want to use), the result is a video signal that contains only part of the PC’s video signal and NONE of the TV signal. Because the TV tuner worked perfectly with the desktop that I used it with previously (which had a VGA output), I have to believe that the problem has something to do with the UD-3900, i.e. something in the UD-3900’s video signal that is essential in the “merging” of the TV video signal with the PC video signal by the TV tuner, is missing or has been altered in some way by the DisplayLink chip.

Any thoughts? Does anyone know which specific DisplayLink chip is used in the Plugable UD-3900 docking station? If I can find that out, I might be able to contact DisplayLink and ask some more specific technical questions about the video signal.
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Old 04-20-2017, 08:05 AM   #2
AlbanRampon
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Hello GTM,

Thank you for the details.
Could you please give some information about the monitor in use and gather the logs files when everything is plugged in?
The third link in my forum signature explains how to do this and ZIP files can only be downloaded by DisplayLink employees here.

Kind regards,
Alban
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Old 04-22-2017, 03:03 PM   #3
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The monitor being used is an Acer P221W, and I'm using the VGA input because the external TV tuner is a VGA-only device.

I don't believe log files are going to help at all in this case because the external TV tuner is a stand-alone device that sits between the UD-3900 and the monitor. Since it requires no installation in Windows whatsoever (no drivers, etc), Windows does not even know that it's there. Any log files generated by the UD-3900 can't possibly contain information about the TV tuner because the UD-3900 also does not know that the TV tuner is there (for the same reason that Windows doesn't know it's there). Unless there is some kind of feedback to the UD-3900 about the video signal at the monitor's input (which seems highly unlikely), the UD-3900 simply outputs the video signal as it should, and the monitor perfectly displays all video information coming from the laptop only AND the video signal coming from the TV tuner only (when the TV tuner is set to 'full-screen' mode). The problem occurs only when the TV tuner is set to display the TV signal in the small always-on-top window, where it has to "merge" the video signal from the laptop with the TV video signal.

The TV tuner undoubtedly does some sort of digital signal processing, but it does this INTERNALLY after it converts both the analog VGA signal from the laptop and the analog TV signal from the 75-ohm cable to digital signals. It then converts the digitally-processed signal back to analog VGA to output to the monitor. It does all of this on its own, without the knowledge of Windows (and thus without the knowledge of the laptop or the UD-3900).

I'm thinking that something about the video signal from the UD-3900's DisplayLink chip is slightly different than the video signal from the video card in the desktop that I previously used the TV tuner with (with no problems in any mode). Can you give me any details about the video signal that's output by the DisplayLink chip in the UD-3900, e.g. what specific video standard(s) does it meet, what version of those standard, etc?
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Old 04-22-2017, 06:22 PM   #4
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The monitor has a channel to talk with the device and this is captured in logs. There are also indications of the mode being set, with which timings.
You are putting something in the middle, so it has an influence anyway.

Without any data, I am unable to see how I will be able to help.
The chip passes the conformance of the different standard it is supposed to implement. This is checked with different test equipment in our labs with protocol analyzers, by third parties as well, and interoperability is also tested. The fact you have two devices implementing a standard is unfortunately by no mean a guarantee they will work together. That's why you have so many "plugfests" in the electronics industry.

May I get these logs now, please, when the issue is present?

Kind regards,
Alban
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Old 04-23-2017, 02:31 PM   #5
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Log files attached. Note that since the instructions in the "How can I report Windows installation issues to DisplayLink" article seemed to be for problems with the installation or removal of the DisplayLink software, and that isn't what my problem is, here are the steps I followed to create the log files for my specific problem:

1. Download 'Windows DisplayLink Support Tool'.
2. Run the tool.
3. Click on 'Advanced Options'.
4. Check the "On" radio button under 'Advanced Installer Logging'.
5. Check the "On" radio button under 'Advanced DisplayLink Logging'.
6. Switch the external TV tuner from its default 'PC mode' (where it displays the PC video signal only) to 'full-screen TV mode' (where it displays the TV signal only). THIS MODE WORKS FINE.
7. Switch the external TV tuner back to 'PC mode' after ~ 10 seconds in 'full-screen TV' mode.
8. Switch the external TV tuner from 'PC mode' to 'window TV' mode (where it displays the PC video signal and the TV signal in a small always-on-top window). THIS MODE DOES NOT WORK: instead, it displays a partial PC video signal and no TV video signal. It stays in this mode for ~ 5 seconds and then reverts to 'full-screen TV' mode on its own (this must be a feature of the external TV tuner).
9. Click on 'Gather Support Information'.
10. Click the "Turn Off" radio button under 'Advanced Installer Logging'.
11. Click the "Turn Off" radio button under 'Advanced DisplayLink Logging'.
12. Close the tool.

So basically I didn't install or uninstall the DisplayLink software, and I didn't reboot my PC. If the steps I followed are incorrect, please let me know how to correct them and I'll send a new log.

Thank you!
Attached Files
File Type: zip DESKTOP-30G3GMI_20170423_095405.zip (1.88 MB, 3 views)
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Old 04-23-2017, 04:51 PM   #6
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Hello GTM,

Thank you for the logs.
Windows indicates that there is one ACER P221 monitor connected at 1680x1050.
The following article I found online claims the max resolution of the Box 9 is 1280x1024.
http://ixbtlabs.com/articles2/aver-box9/

Do you use two monitors simultaneously on this machine?
Can you check which resolution the box expects and which resolution is in the Display settings menu?

I don't see the EDID file from the monitor in the logs and USB errors are filling the logs so I don't see what resolution the dock is actually sending.
Seeing a partial display would fit with having the tuner video mixer not being to able to cope with the resolution.

Kind regards,
Alban
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Old 04-23-2017, 08:56 PM   #7
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I'm only using one monitor - the Acer P221W.

If I set the resolution from the Windows desktop (right-click --> Display settings --> Advanced display settings --> Resolution) to 1280 x 1024, and then set the TV tuner box resolution to the same 1280 x 1024 resolution (using its on-screen configuration menu), I get essentially the same results that I've been getting: in 'full-screen TV' mode the entire TV video signal is perfectly visible (as it should be), but in 'window TV' mode I see almost the entire PC video signal (a bit of the bottom is truncated) - more than when the resolution of the TV tuner and the resolution set in Windows matched - but NO TV SIGNAL AT ALL, and after a few seconds in 'window TV' mode the TV tuner box reverts back to 'full-screen TV' mode on its own.

Should I be concerned about USB errors filling the logs? What are these errors? It seems important that you can't see what resolution the UD-3900 is sending.

What about the lack of the EDID file from the monitor: is that a concern? Why is it missing? I'm using a 3rd-party DVI-to-VGA adapter that I purchased, instead of the DVI-to-VGA adapter that was shipped with the UD-3900. I believe I've tried both, but I can retry the one that was shipped with the UD-3900 if you think that could matter.

What about the driver for the UD-3900: am I using the most recent version? Could that matter in this case?
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