Customer reported sporadic errors when playing mp4 videos inside an ICA session, Windows Media Player throws an error "An Error occurred while playing the file".
Users have to try a few times to get video to play.

Workaround:

Have tested it on the following platforms: XenDesktop 7.6 / 7.6CU1 / 7.6 CU2 / 7.6CU3 / 7.13 Win7/Win10/Win2008/Win2016

A new register item needs to be added on the VDA side:

32bit System:
Add a new item "UseDefaultRenderers" at the path "HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\HDXMediaStream".
Set the value as 1.
The type is DWORD.

64bit System:
Add a new item "UseDefaultRenderers" at the path "HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\HdxMediaStream".
Set the value as 1.
The type is DWORD.

The workaround applies to scenarios where Multimedia Redirection is disabled and play mp4 file failed.

Please don't use it when the Multimedia Redirection is enabled.

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Problem Cause

Code changes introduced by MS in Media Player.

This article describes an error you might encounter when you explicitly disable multimedia redirection in an ICA session.