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November 25th, 2017 05:00
Latitude 5580 + TB16 dock = bad HDMI quality to TV
Hi,
I've got a Latitude 5580 + a Samsung UE40K5500AK.
When connecting the laptop straight with the TV, I get stunning image quality.
When connecting the laptop to the TB16 Thunderbolt dock and the dock with the TV with HDMI, the image quality drops drastically.
All drivers are up to date and TV settings are correct. It's only when using the dock that the quality drops.
Is this expected behavior? If not, any suggestions what could be wrong?
The TV does not support DisplayPort, so using different interface is not an option.
Thanks,
Manos
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jphughan
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November 25th, 2017 07:00
Can you be more specific on the quality drop? Is that resolution, refresh rate, color, what? Is the dock/TV maybe defaulting to a lower resolution when connected through the dock? If so, does just changing the resolution in Display Settings fix it? Also note that the dock actually supports a newer HDMI standard (2.0) than the system itself (1.4), which means thst connecting through the dock allows support for configurations like 4K @ 60 Hz with HDR or Full RGB (4:4:4), whereas HDMI 1.4 only allows 4K @ 24 Hz with YUV (4:2:0). So maybe your TV is seeing the higher capabilities of the dock and then trying and failing to negotiate a higher standard. But you should still be able to change settings manually, although you might need to use the Intel Display Settings for things like color space.
Lastly, is your TV firmware up to date?
eandroul
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November 28th, 2017 16:00
It is like when you reformat a picture from BMP to JPEG, where due to the compression you introduce some noise.
Not the best idea but I tried taking some photos from my phone.
This is the one with direct connection: Laptop -> HDMI -> TV :
drive.google.com/.../view
And this is the one with connection: Laptop -> Thunderbolt -> Dock TB16 -> HDMI -> TV :
https://drive.google.com/file/d/1xzh8uYlBfewcCwU0RJPvlRH0gW_tatMC/view?usp=sharing
Those thwo pics were taken from exactly the same configuration. Both when connecting through the dock or straight to the TV, the resolution is the same at 1920x1080. While screen refresh rate is at 60 Hz.
I've tried different refresh rates and I could see for example the mouse lagging on display a little bit but the quality didn't change. I've also tried different resolutions but again I would still get this type of distortion of quality.
The TV FW is up to date.
Also I've reinstalled all the following drivers in the specified order 1-to-9, but I still get the same quality drop.
http://www.dell.com/support/article/uk/en/ukdhs1/sln304347/dell-thunderbolt-dock-tb16-driver-installation-guide?lang=en
Is this something that has been noticed before? Could the dock be faulty in such way?
Thanks,
Manos
jphughan
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14K Posts
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November 29th, 2017 06:00
It's tough to tell from those pictures, but that looks like it could be a color space selection issue. It's possible that one mechanism is using full RGB while the other is using YUV, which isn't something that shows up in the regular Windows Display Settings but should show up in the Intel Graphics Settings. Normally I'd expect the dock's newer HDMI standard support to be equal or better, but HDMI still has its quirks sometimes.
But to answer your last question, no I personally haven't seen issues like this reported with the dock, but again I suspect this is a weird firmware issue that may only affect certain combinations of devices, like that dock and your TV. Still, if looking at the Intel settings while connected two different ways reveals a difference, you may be able to force the appropriate change while connected via the dock to obtain proper image quality.