Product Documentation

Known and fixed issues

Apr 29, 2016

General known issues


Editing the registry incorrectly can cause serious problems that may require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

  • Skype for Business might crash at startup after RealTime Connector is installed. Workaround:  Restart Skype for Business.  [#608171]
  • Sound issues might occur due to Windows Defender. For example:  [#610394, #612143]:
    • Call arrives and the ring tone plays incorrectly with interruptions at irregular intervals.
    • Dual Tone Multiple Frequencies (DTMF) playback was erratic making it difficult to tell which digit was entered.
    • Discontinuous (“stutter”) ringing and Ringback tones

Workaround: Citrix recommends you do the following in a proactive fashion for all for Windows 8.1 and Windows 10 VDAs:
1. Click Start and type Defender.
2. Choose the Windows Defender settings option.
3. Scroll down to Exclusions and click Add an exclusion.
4. Click Exclude a .exe, .com or .scr process.
5. Navigate to where Skype For Business is installed (C:\Program Files\Microsoft Office\Office15). 
6. Choose Lync.exe and click Exclude this file.

  • In Fallback mode (when RealtTime Media Engine is not available on the endpoint and audio/video processing occurs on the server), video quality might degrade to the point of failure on virtual desktops with a single virtual CPU. Workaround: Change the VDA configuration to have a minimum of two CPUs for users who may encounter Fallback mode. For more information, see and[#611616]
  • Video might stop displaying during a PowerPoint presentation. Workaround: Each user should advance the slide to make video reappear. [#606460]
  • The Video Preview button in the Video Setting page is not implemented (fixed in version 2.0.100). [LOP-577] 
  • The originator of a conference call might not see the active speaker.  All other participants in the call do see the active speaker.  [#610397]
  • The video portion of a conference call conversation window turns black for several seconds and recovers when the user mutes himself/herself.  [#601666]
  • Some headset devices (for example, Polycom and Plantronics) are mistaken for speaker phone or handset devices.  Workaround: Restart Skype for Business [#605349]
  • If Citrix Receiver for Mac 12.0 is on the endpoint device and a Human Interface Device (HID) is removed after Skype for Business and RealTime Optimization Pack are running, the RealTime Media Engine might crash. Workaround: Upgrade your version of Citrix Receiver for Mac to 12.1. [#612448]
  • When a RealTime Optimization Pack user is participating in a conference as an attendee, and the conference organizer initially disables and then re-enables attendee video, the Skype for Business UI (the video icon) does not correctly reflect the current state of sending video to the conference. When attendee video is enabled, the participant’s video is sent to the conference, but the video icon is still crossed-out, indicating disabled video. [#612875]
  • In various scenarios while in a video call, the video window shows through and overlaps other items on the screen (fixed in version 2.0.100). [#600340, #612451, #608456, #612452] For example, while in a video call:
    • Click on Start menu
    • Ctrl-Alt-Delete
    • Change from one desktop to others
  • When making video calls to several users, video rendering might stop on one or more users and will be replaced with a blue screen. Possible workaround:  Users might regain video if they leave the conference and are invited back in. [#606791, #610763]
  • Incorrect video placement might occur when the video for one or more users is put on hold or is stopped.  [#612389, #604255, #611398]
  • Skype for Business might crash when exiting a video conference call or when exiting from the notification area. [#612444, #612115, #610894]
  • When the Skype for Business client is delivered as a published application, desktop sharing is not supported and should not be used as the server desktop will be shared rather that the local desktop. Application sharing can be used to share other hosted applications during a Skype for Business call. [#571502]
  • There might be problem dialing dual tone multi frequency (DTMF) digits using a Jabra Pro 9465 device on a Linux client. Workaround: Use the RealTime Optimization Pack interface to dial the DTMF digits. [#547234]
  • The microphone volume level of the Polycom CX100 speakerphone is very low even at its full level when used with the HP Thin Pro client. [#604219]

    Workaround: You can modify the registry key that comes with the HP Thin Pro comes by using the regeditor program on the client, which can be run as root, or from the Registry Editor component of the Profile editor.

    These settings limit the range of available settings on the input volume slider.  The RecordScale default value of 100 limits it to 25% of its maximum value for the microphone jack.  Setting RecordScale to the maximum value of 400 allows the slider access to the entire scale.


    Value name: RecordScale
    Value data: 400 (Default is 100)

    Value name: RecordScaleAuto -
    Value data: 0 (Default is 1- sets to 100)

    1         Sets RecordScale value based on  hardware type.

    2         Does not set RecordScale value based on hardware type.

    For playback, these controls work the same way as the input volume controls.


    Value name: OutputScale
    Value data: 400 (Default is 100)

    Value name: OutputScaleAuto
    Value data: 0 (Default is 1)

  • Users might hear an echo or other artifacts when using any built-in microphone and speakers on endpoints. Workaround: Use a headset on an endpoint or a speakerphone with hardware-based echo cancellation. [#545463]
  • When attempting to make high-definition video calls from a home office, take into account your users' network bandwidth and ISP routing policies. If you observe pixilation of the video or problems with lip sync, adjust the Maximum Packet Size (MTU) on the network interface card properties to a lower value such as 900 to avoid situations where ISPs perform traffic shaping based on packet size.
  • Citrix RealTime Optimization Pack 2.0, does not appear in the Citrix Receiver for Windows Support Infogenerated from the Advanced Preferences menu. [#608200, LOP-650]
  • Citrix RealTime Optimization Pack 2.0 does not support the Plantronics Clarity P340 audio device. [#597048, 603639, 608218]
  • Various scenarios (for example, combining content sharing and audio/video conferencing) might not work properly when some conversation participants run previous versions of the RealTime Optimization Pack. Workaround: Participants using older versions of HDX RealTime Optimization Pack should upgrade to HDX RealTime Optimization Pack 2.0. [#609018]

HDX RealTime Media Engine known issues

  • For Citrix Receiver for Windows versions  4.2 and earlier - Uninstalling the Citrix Receiver, uninstalls HDX Real Time Media Engine. You must reinstall HDX Real Time Media Engine after installing Receiver. For more information, see [#484913]
  • Sometimes, when attempting to install HDX RealTime Media Engine on Windows, a message indicates that there is no available disk space. However, limited space does exist on the Z:/ drive of the terminal. This is a known issue for Microsoft installers and applies to Citrix Receiver as well.
  • Linux might mistake some audio devices containing buttons for a Human Interface Device (mouse) instead of an audio device. When a user presses a button, Linux interprets it as a mouse button press and prevents the regular mouse from working correctly until the call is terminated. Workaround: Configure the Linux X11 graphics subsystem to ignore the devices as sources of user input by creating or modifying the xorg.conf configuration file with the following sections (for example, Jabra, Plantronics, or Sennheiser). [#521088]
    Section "InputClass"
    Identifier "Jabra"
    MatchVendor "Jabra"
    Option "Ignore" "True"
    Section "InputClass" 
    Identifier "Plantronics" 
    MatchVendor "Plantronics" 
    Option "Ignore" "true" 
    Section "InputClass" 
    Identifier "Sennheiser" 
    MatchVendor "Sennheiser|1395" 
    Option "Ignore" "true" 
  • During installation or un-installation, it is possible to encounter certain error conditions where the error message string is not localized. [#14530, #93]
  • In Seamless mode, the following issues exist for Full Screen video:
    • Full Screen video appears in letterbox format with the Linux version of the RealTime Media Engine in Seamless mode. [#13564]
    • The Full Screen Control hides behind other apps in a Seamless session in XenApp Seamless mode. [#10731, #3]
  • The HDX RealTime Media Engine does not support calls with users on Skype for Business-compatible IP phones configured to use the master key identifier (MKI) field in encrypted media packets.
    Workaround: Reconfigure those phones to disable MKI but keep encryption enabled.

Third party issue

When external Optimization Pack users participate in Skype for Business calls, application, desktop, and file sharing between internal and external users might fail. [#LOP-942]