Audio features 编辑

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

Although it is best to deliver audio using User Datagram Protocol (UDP) rather than TCP, UDP audio encryption using DTLS is available only between NetScaler Gateway and Citrix Receiver. Therefore, sometimes it might be preferable to use TCP transport. TCP supports end-to-end TLS encryption from the VDA to Citrix Receiver.

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.

When bandwidth is limited, for example satellite or dial-up connections, reducing audio quality to Low consumes the least possible bandwidth. In this situation, create separate policies for users on low-bandwidth connections so that users on high-bandwidth connections are not adversely impacted.

For setting details, see Audio policy settings. Remember to enable Client audio settings on the user device; see “Audio setting policies for user devices” later in this article.

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 puts extra 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” later in this article.

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” later in this article.

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 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” later in this article.

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

By default, Audio over User Datagram Protocol (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. For real time audio such as softphone applications, UDP audio is now preferred more than EDT. UDP allows for packet loss without retransmission, ensuring that no latency is added on connections with high packet loss.

Important:

Audio data transmitted with UDP is not encrypted when NetScaler Gateway is not in the path. If NetScaler Gateway is configured to access XenApp and XenDesktop resources then audio traffic between the endpoint device and NetScaler Gateway is secured using the 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 is 16500–16509.

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” later in this article.

Audio setting policies for user devices

1. Load the group policy templates by following Configuring the Group Policy Object administrative template.
2. In the Group Policy Editor, expand Administrative Templates > Citrix Components > Citrix Receiver > User Experience.
3. For Client audio settings, select Not Configured, Enabled, 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 Gateway, select Allow Real-Time Transport Through gateway. NetScaler Gateway must 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.

; 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
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