HDX – Fuzzy images with Thinwire+

– Guest Blog from my colleague Steffen Buck (@buck_steffen)

With this blogpost I will tell you the story about fuzzy images within a Citrix XenApp environment. Julian and I worked together in a customer project. The customer has a bunch of branch offices with different bandwidths. In the headquarter and in the most branch offices, everything went smooth without any complaints about graphic performance or something like that.

One branch site with a few people and a synchronous bandwidth of 2 MB/s complaint about poor image quality within different types of work. For example, reading PDF documents, images within webpages, and so on. All the images that are displayed within the citrix session are mosaic / block like with a poor quality. After a few seconds the blocks disappear randomly, but it could take up to 20 seconds until all blocks are gone and the image was displayed correctly.

This behavior occurs, no matter what HDX policies are set:
Visual Quality: High / Medium / Low
Color depth: 8bit / 16bit / 24 bit

Attached you can find an example of the Citrix website directly after opening and after ~10 seconds:

pic1.png

pic2.png

After a long troubleshooting session I found the article about progressive display mode, which was implemented with the version 7.18 of the VDA:

https://support.citrix.com/article/CTX235349

Yeah, that exactly describe our situation at the customer branch office.

And of course, with this information that make sense and it works as expected.

“HDX Thinwire will now switch to a progressive update mode if available bandwidth dips below 2 Mbps, or network latency drifts above 200ms.”

After disabling the progressive mode with the following registry key, all the images were shown in high quality at the beginning of viewing it.

Path: HKLM\Software\Citrix\Graphics
Type: REG_DWORD
Name: ProgressiveDisplay
Value: 0

Fuzzy second 😊

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