Product Documentation

Audio features

Jun 13, 2017

You can configure and add the following Citrix policy settings to a policy that optimizes HDX audio features. For usage details plus relationships and dependencies with other policy settings, see Audio policy settings and Bandwidth policy settings and Multi-stream connections policy settings.

Important: Most audio features are transported using the ICA stream and are secured in the same way as other ICA traffic. User Datagram Protocol (UDP) audio uses a separate, unsecured, transport mechanism when NetScaler Access Gateway is not in path. If NetScaler Access Gateway is configured to access XenApp and XenDesktop resources, then UDP audio traffic between the endpoint device and NetScaler Access Gateway is secured using DTLS protocol. 

Audio quality

In general, higher sound quality consumes more bandwidth and server CPU utilization by sending more audio data to user devices. Sound compression allows you to balance sound quality against overall session performance; use Citrix policy settings to configure the compression levels to apply to sound files.

By default, the Audio quality policy setting is set to High - high definition audio when TCP transport is used, and to Medium - optimized-for-speech when UDP transport (recommended) is used. The High Definition audio setting provides high fidelity stereo audio, but consumes more bandwidth than other quality settings. Do not use this audio quality for non-optimized voice chat or video chat applications (such as softphones), because it may introduce latency into the audio path that is not suitable for real-time communications. The optimized for speech policy setting is recommended for real-time audio, regardless of the selected transport protocol. 

Consider creating separate policies for groups of dial-up users and for those who connect over a LAN or WAN. Over connections where bandwidth is limited, download speed is often more important to users than sound quality. Therefore, you may want to create one policy for low speed connections that applies high compression levels to sound, and another for LAN or WAN connections that applies lower compression levels.

For setting details, see Audio policy settings. Remember to enable Client audio settings on the user device; see Audio setting policies for user devices.

Client audio redirection

To allow users to receive audio from an application on a server through speakers or other sound devices (such as headphones) on the user device, leave the Client audio redirection setting at its default (Allowed).

Client audio mapping may cause a heavy load on the servers and the network; however, prohibiting client audio redirection disables all HDX audio functionality.

For setting details see Audio policy settings. Remember to enable client audio settings on the user device; see Audio setting policies for user devices.

Client microphone redirection

To allow users to record audio using input devices such as microphones on the user device leave the Client microphone redirection setting at its default (Allowed).

For security, users are alerted when servers that are not trusted by their user devices try to access microphones, and can choose to accept or reject access prior to using the microphone. Users can disable this alert on Citrix Receiver.

For setting details, see Audio policy settings. Remember to enable Client audio settings on the user device; see Audio setting policies for user devices.

Audio Plug N Play

The Audio Plug N Play policy setting allows or prevents the use of multiple audio devices to record and play sound. This setting is Enabled by default. Audio plug n play enables audio devices to be recognized even if they are not plugged in until after the user's session has been established.

This setting applies only to Windows Server OS machines.

For setting details, see Audio policy settings.

Audio redirection bandwidth limit and Audio redirection bandwidth limit percent

The Audio redirection bandwidth limit policy setting specifies the maximum bandwidth (in kilobits per second) for a playing and recording audio in a session. The Audio redirection bandwidth limit percent setting specifies the maximum bandwidth for audio redirection as a percentage of the total available bandwidth. By default, zero (no maximum) is specified for both settings. If both settings are configured, the one with the lowest bandwidth limit is used.

For setting details, see Bandwidth policy settings. Remember to enable Client audio settings on the user device; see Audio setting policies for user devices.

Audio over UDP Real-time Transport and Audio UDP port range

By default, Audio over UDP Real-time Transport is allowed (when selected at time of installation), opening up a UDP port on the server for connections that use Audio over UDP Real-time Transport. Citrix recommends configuring UDP/RTP for audio, to ensure the best possible user experience in the event of network congestion or packet loss.
Important: Audio data transmitted with UDP is not encrypted when NetScaler Access Gateway is not in path. If NetScaler Access Gateway is configured to access XenApp and XenDesktop resources then audio traffic between the endpoint device and NetScaler Access Gateway is secured using DTLS protocol.

The Audio UDP port range specifies the range of port numbers that the Virtual Delivery Agent (VDA) uses to exchange audio packet data with the user device.

By default, the range is16500 - 16509.

For setting details about Audio over UDP Real-time Transport, see Audio policy settings; for details about Audio UDP port range, see Multi-stream connections policy settings. Remember to enable Client audio settings on the user device; see Audio setting policies for user devices.

Audio setting policies for user devices

  1. Load the group policy templates by following Configure Receiver with the Group Policy Object template.
  2. In the Group Policy Editor, expand Administrative Templates > Citrix Components > Citrix Receiver > User Experience.
  3. For Client audio settings, select Not ConfiguredEnabled, or Disabled.
    • Not Configured. By default Audio Redirection is enabled with high quality audio or previously configured custom audio settings.
    • Enabled. Audio redirection is enabled with selected options.
    • Disabled. Audio redirection is disabled.
  4. If you select Enabled, choose a sound quality. For UDP audio, use Medium (default).
  5. For UDP audio only, select Enable Real-Time Transport and then set the range of incoming ports to open in the local Windows firewall.
  6. To use UDP Audio with NetScaler Access Gateway, select Allow Real-Time Transport Through gateway. NetScaler Access Gateway should be configured with DTLS. For more information, see UDP Audio Through a Netscaler Gateway.

As an Administrator, if you do not have control on endpoint devices to make these changes, for example in the case of BYOD or home computers, then use the default.ica attributes from StoreFront to enable UDP Audio.

  1. On the StoreFront machine, open C:\inetpub\wwwroot\Citrix\<Store Name>\App_Data\default.ica with an editor such as notepad.
  2. Make the entries below under the [Application] section.
command 복사

; This is to enable Real-Time Transport

EnableRtpAudio=true

; This is to Allow Real-Time Transport Through gateway

EnableUDPThroughGateway=true

; This is to set audio quality to Medium

AudioBandwidthLimit=1-

; UDP Port range

RtpAudioLowestPort=16500

RtpAudioHighestPort=16509

If UDP Audio is enabled by editing default.ica, then UDP audio will enabled for all users who are using that store.

Avoid echo during multimedia conferences

Users in audio or video conferences may hear an echo. Echoes usually occur when speakers and microphones are too close to each other. For that reason, Citrix recommends the use of headsets for audio and video conferences.

HDX provides an echo cancellation option (enabled by default) that minimizes echo. The effectiveness of echo cancellation is sensitive to the distance between the speakers and the microphone; devices should not be too close or too far away from each other.

You can change a registry setting to disable echo cancellation. When working in the registry, use caution: 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.
  1. Using the Registry Editor on the user device, navigate to one of the following:
    • 32-bit computers: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio\EchoCancellation
    • 64-bit computers: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio\EchoCancellation
  2. Change the Value data field to FALSE.