About this release

What’s new

What’s new in 2.8.100

RealTime Media Engine enhancement

The RealTime Media Engine now supports Citrix Workspace app for Android 64-bit architecture in addition to 32-bit. This enhancement requires Citrix Workspace app 1910 for Android.

What’s new in 2.8

Enhanced audio quality

Enhanced audio quality because of the improved echo cancellation on Windows.

Remote connectivity

Support for Skype for Business calls when the Edge server is not reachable. In these cases, the Optimization Pack goes into fallback mode and audio and video processing occurs on the server.

Fixed issues

Fixed issues in 2.8.100

There are no fixed issues in this release.

Fixed issues in 2.8

This release contains fixes to many customer-reported issues and continues to add stability and ease of use to the HDX RealTime Optimization Pack.

  • During a Skype for Business video call, loss of the mouse functionality might occur. The mouse clicks stop working on the taskbar after you right-click on the video window. [LD0280]

  • A media stream might not be established when a call is made between the HDX RealTime Optimization Pack and the BT TPO gateway. [LD0719]

  • When using Skype for Business with the HDX RealTime Optimization Pack, the Skype for Business Server Monitoring Reports might indicate high jitter values. [LD0720]

  • When you host a meeting using the Cisco Meeting Server (CMS), the remote video displayed on the HDX RealTime Optimization Pack endpoint might become unresponsive. [LD0736]

  • An issue might occur during an audio call between User1 and User2. User1 has the HDX RealTime Optimization Pack installed and User2 has the native Skype for Business installed. The call might drop when both users attempt to add videos simultaneously. [LD0807]

  • When a call is established between two users, the call might be declared as dead when any one user puts the call on hold before the final Session Description Protocols (SDPs) are exchanged. [LD0868]

  • When certain headset devices are connected to a client endpoint with the RealTime Media Engine, a dial tone might play when you open Skype for Business. [LD1026]

  • When you use a hosted shared desktop that has the HDX RealTime Optimization Pack installed, the Optimization Pack connection might disconnect and reconnect randomly. A hosted shared desktop is a published desktop running on a remote desktop server.[LD1130]

  • Video capture issues sometimes occur when using a Logitech 310 camera and the Citrix Ready workspace hub. The Preview option might not work, call initialization might be slow, calls placed on hold might not resume, or the camera fails during a call [LOP-2268]

  • Chrome OS users might experience a slight delay in video synchronization if the incoming video is sent from a device that doesn’t support hardware encoding. [LOP-3058]

  • When a Mac user upgrades the RealTime Media Engine to version 2.6, a message requesting the keychain password might appear. To enable this fix, choose one of these options:

    Allow - allows the permission only once and the user must enter the keychain password again when the Citrix Workspace app for Mac invokes the RealTime Media Engine.

    Deny - doesn’t allow the RealTime Media Engine to collect crash reports provided by the HockeyApp.

    Always Allow - the user no longer receives a prompt for that particular keychain entry. The user has to choose this option once for every keychain entry. [LOP-3286]

  • The incoming calls might fail to register and the calls are directed to voice mail. The issue occurs when the subnet where the HDX RealTime Optimization Pack is located is not recognized. This fix supports Location-Based Routing for incoming calls. [LOP-3515]

  • The RealTime Optimization Pack 2.8 with Citrix Workspace app for Linux 18.10 and above, supports multimedia redirection for all 32-bit applications. [LOP-3683]

Known issues


Editing the registry incorrectly can cause serious problems that might 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.

General known issues

  • If Mac OS X user changes the dock UI setting while Skype for Business is running, current and future calls don’t display local or remote video. [LOP-1062]

    Workaround: Restart Skype for Business.

  • When fallback mode is set to audio only, and the users in fallback mode participate in a video conference, they might see their own states in the participant list incorrectly displayed as On Hold. Other users are not affected. [LOP-1175]

  • If a caller plugs in another human interface device (HID) during an active call, the call might drop. [LOP-1377]

  • After the called party using an IP phone accepts a video call as audio-only, the caller cannot add a third participant to turn the call into a conference call.

    Workaround: The called party can add the third participant, after which all conferencing capabilities are available. [LOP-1504]

  • The Optimization Pack is not compatible with the Polycom RealPresence Trio 8800. If you use the Skype for Business UI to accept a call, but use the Polycom RealPresence Trio 88 to hang up the call, the call doesn’t end. [LOP-1983]

  • Video capture issues sometimes occur when using a Logitech 9000 camera and the Citrix Ready workspace hub. The Preview option might not work, call initialization might be slow, calls placed on hold might not resume, or the camera fails during a call [LOP-2339]

  • When starting an audio point-to-point call and starting video at the same time, a Cannot start video message appears. [LOP-2356]

    Workaround: Do not start an audio point-to-point call and video at the same time.

  • In point-to-point calls using a UVC camera, or in a Meet Now, before a user starts transmitting video, the aspect ratio of the picture-in-picture video window might not display in the correct aspect ratio. On point-to-point calls, the video you’re sending might be wider and include more content than what is visible in the picture-in-picture window. In Meet Now, after each participant becomes an active speaker, the aspect ratio changes to 16:9. [LOP-2462]

  • When a call is started on a Chrome OS device using a webcam microphone and a Polycom CX100 speaker or a built-in speakerphone/microphone, echo cancellation might not work. The remote participant in the call might hear their own voice at a low volume. Background sounds from the originator can also be heard. [LOP-3082]

  • While changing resolution in a peer-to-peer or conference video call, the RealTime Media Engine on the Chrome OS might display a black frame for approximately 1 to 2 seconds. [LOP-3207]

  • Calls might be blocked and the Connecting state appears in the tooltip while the RealTime Connector initializes. The blocked call leaves and open Skype window indicating that the call ended. The hang up button is unresponsive and you must use the X in the upper right corner to close the window. [LOP-3634]

  • In a call between two Windows users, if both speak at the same time, and one of them is doing software-based acoustic echo cancellation, one user might hear some echo. [LOP-3740]

  • Optimization Pack, does not appear in the Citrix Receiver for Windows Support Info generated from the Advanced Preferences menu. [608200, LOP-650]

  • 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. [612448]

    Workaround: Upgrade your version of Citrix Receiver for Mac to a more recent version.

HDX RealTime Media Engine known issues

  • When a user (user2) on a Mac tries to use the RealTime Media Engine that another user (user1) installed, user2 might not receive an optimized experience. [LOP-2203]

    Workaround: On a Mac, install the RealTime Media Engine by using the actual user’s logon.

  • In Seamless mode, the following issues exist for the Full Screen video:
    • Full Screen video appears in the 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]

  • During installation or uninstallation, it is possible to encounter certain error conditions where the error message string is not localized. [14530, 93]

  • 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 issue is a known issue for Microsoft installers and applies to Citrix Receiver as well.

Citrix Ready workspace hub issues

  • When you use the RealTime Media Engine on the Citrix Ready workspace hub, the buttons on audio devices that have Human Interface Design (HID) functions do not work. You can use these devices as plain audio devices. [LOP-1634]

  • Connecting a USB audio device to the Citrix Ready workspace hub while Skype for Business is running might cause a loss of the wired Ethernet connection. For optimal performance, we recommend that you connect your USB video camera and audio device to the Citrix Ready workspace hub as part of your setup procedure. If you lose the wired Ethernet connection because of disconnecting or reconnecting a USB device, restart the Citrix Ready workspace hub. [LOP-2523]

  • Acoustic echo cancellation might not work. Using the Citrix Ready workspace hub with a microphone and speakers might generate echo that the other parties to the call hear. [LOP-2538]

  • On the Citrix Ready workspace hub and a Stratodesk image using XenDesktop 7.6, the Picture in Picture and incoming video windows might appear as blue screens. [LOP-2588]

    Workaround: Disable the HDX 3D Pro H.264 acceleration.

Third party issues

  • You might encounter errors with Skype (not Skype for Business) on iOS 9.2. [LOP-1313]

    Workaround: Upgrade to iOS 9.3.2

  • RealTime Optimization Pack video appears in the letter box format. When the video is sent to native Skype for Business, native Skype for Business might crop and zoom the video to fit it into a square format. [LOP-2431]

  • Because of changes to the privacy policies in Microsoft Windows, audio and video calls might fail in fallback mode on VDAs. For more information, see Windows 10 camera, microphone, and privacy. [LOP-3460]

    Workaround: Enable access to the microphone.

  • User1 might hear “underwater” (partially canceled echo) noise during the echo cancellation process. This issue can occur when User2’s microphone is sensitive to the input audio. [LOP-3742]

  • 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 ends. [521088]

    Workaround: Configure the Linux X11 graphics subsystem to ignore the devices as sources of the user input. Create or change a .conf file in the /usr/share/X11/xorg.conf.d directory with the following sections (for example, Jabra, Plantronics, or Sennheiser).

    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”


  • The microphone volume level of some Linux clients is low.

    Workaround: Increase the microphone level using the Linux system volume control.

  • There might be a problem dialing dual-tone multi-frequency (DTMF) digits using a Jabra Pro 9465 device on a Linux client. [547234]

    Workaround: Use the RealTime Optimization Pack interface to dial the DTMF digits.

  • Citrix RealTime Optimization Pack does not support the Plantronics Clarity P340 audio device but does support the P340-M (Skype for Business qualified device). [597048, 603639,608218]

  • The microphone volume level of the Polycom CX100 speakerphone is low even at its full level when used with the HP Thin Pro client. [604219]

    Workaround: Change the registry key that comes with the HP Thin Pro by using the regeditor program on the client. You can run the program 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 the RecordScale value based on the hardware type.

    2 Does not set the RecordScale value based on the 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)