Product Documentation

Optimize audio features

Mar 19, 2015
To optimize HDX audio features, use the following Citrix policy settings:
  • Audio quality
  • Client audio redirection
  • Client microphone redirection
  • Audio Plug N Play
  • Audio redirection bandwidth limit
  • Audio redirection bandwidth limit percent
  • Audio over UDP Real-timeTransport
  • Audio UDP port range
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.

Select audio quality

In general, higher sound quality consumes more bandwidth and greater 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, Audio quality is set to High - high definition audio. This setting provides high fidelity stereo audio; however, it consumes more bandwidth than other quality settings.
Note: Do not use this audio quality for non-optimized voice chat or video chat applications (such as softphones), as it may introduce latency into the audio path that is not suitable for real-time communications.

Consider creating separate policies for groups of dial-up users, and for those who connect over a LAN or WAN. Over dial-up connections, where bandwidth typically is limited, users are likely to care more about download speed than sound quality. You may therefore want to create one policy for dial-up connections that applies high compression levels to sound, and another for LAN or WAN connections that applies lower compression levels.

To change audio quality, add the Audio quality setting to a policy and select one of the following audio quality levels:
  • Medium - optimized for speech. Use this setting to deliver Voice over IP (VoIP) applications, or to deliver media applications in challenging network connections with very low (less than 512Kbps) lines or significant congestion and packet loss. Audio sent to the user device is compressed up to 64Kbps; this compression results in a moderate decrease in the quality of the audio played on the user device, while providing low latency and consuming very low bandwidth. If VoIP quality is unsatisfactory with Audio quality set to Medium, ensure that Audio over UDP Real-time Transport policy setting is set to Allowed.
    Note: UDP/RTP requires Audio quality to be Medium.
  • Low - for low-speed connections. Sounds sent to the user device are compressed up to 16Kbps; this compression results in a significant decrease in the quality of the sound, but provides reasonable performance for a low-bandwidth connection.
Important: Remember to enable audio on Client audio settings on the user device, as described later in this document.

Redirect audio reception

You can allow users to receive audio from an application on a server through speakers or other sound devices (such as headphones) on the user device. By default, Client audio redirection is Allowed.

Important: To use this feature, remember to enable audio on Client audio settings on the user device, as described later in this document. On Windows Server OS machines, also ensure that Audio Plug N Play is Enabled to support multiple audio devices.

Client audio mapping may cause a heavy load on the servers and the network; to turn off this feature, add the Client audio redirection setting to a policy and set its value to Prohibited.

Important: When Client audio redirection is Prohibited, all HDX audio functionality is disabled.

Activate user device microphones

You can allow users to record audio using input devices such as microphones on the user device. By default, Client microphone redirection is Allowed; however, if audio is disabled on the client software, or if Client audio redirection is Prohibited, this setting has no effect.

To record audio, the user device needs either a built-in microphone or a device that can be plugged into the microphone jack or USB port. 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.

Important: To use this feature, remember to enable audio on Client audio settings on the user device, as described later in this document. On Windows Server OS machines, also ensure that Audio Plug N Play is Enabled to support multiple audio devices.

To turn off this feature, add the Client microphone redirection setting to a policy and set its value to Prohibited.

Allow multiple audio devices

The Audio Plug N Play policy setting controls whether to allow the use of multiple audio devices to record and play sound. This setting is Enabled by default; to disable this feature, add the Audio Plug N Play setting to a policy and set its value to Disabled.
Note: This setting applies only to Windows Server OS machines.

Set audio redirection bandwidth limits

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.

To configure the Audio redirection bandwidth limit or Audio redirection bandwidth limit percent or both, add the setting to a policy and type a number in the corresponding Value field. If both settings are configured, the one with the lowest bandwidth limit is used.

Important: To use this feature, remember to enable audio on Client audio settings on the user device, as described later in this document.

Send and receive audio with UDP

By default, Audio over UDP Real-time Transport is Allowed, opening up a UDP port on the server to support all connections configured to 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.

By default, UDP audio on XenDesktop uses two consecutive ports within the range of ports 16500 to 16509 to pass through the Windows firewall; the default ports are 16500,16501. To use other ports, add the Audio UDP port range setting to a policy and type the port number or range (in the form lowest port number,highest port number) into the Value field. This setting specifies the range of port numbers used by the Virtual Delivery Agent (VDA) to exchange audio packet data with the user device. The VDA attempts to use each UDP port pair to exchange data with the user device, starting with the lowest and incrementing by 2 for each subsequent attempt. Each specified port handles both inbound and outbound traffic.

Important: To use audio over UDP, remember to enable audio on Client audio settings on the user device, as described below.

Configure audio setting policies for user devices

  1. Expand Administrative Templates > Classic Administrative Templates (ADM) > Citrix Components > Citrix Receiver > User Experience.
  2. For Client audio settings, select Not Configured, Enabled, or Disabled.
  3. If you selected Enabled, choose a sound quality. For UDP audio, use Medium (the default) only.
  4. For UDP audio only, select Enable Real-Time Transport and then set the range of incoming ports to use to pass through the local Windows firewall.

Avoid echo during multimedia conferences

When users take part in audio or video conferences, they may hear an echo in their audio. 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, which minimizes echo during a conference. The effectiveness of echo cancellation is sensitive to the distance between the speakers and the microphone. These devices must not be too close to each other, or too far away from each other.

To disable echo cancellation:

  1. Navigate to the applicable registry entry.
    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.
    • For 32-bit computers: On the user device, open the registry and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio\EchoCancellation.
    • For 64-bit computers: On the user device, open the registry and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio\EchoCancellation.
  2. Change the Value data field to FALSE.