Last year was busy for the Citrix HDX audio team. Audio services underwent a major transformation. In this blog post, we’ll look back at our work from last year and provide guidance on what customers can do to leverage the new audio redirection enhancements in their environment.
Legacy audio redirection solution requires an admin to select the right audio codec for the use case via Citrix policy. In Citrix Virtual Apps and Desktops 2109, we released a new audio codec called adaptive audio, which kickstarted the transformation of audio services. This new audio codec provides dynamic encoding bitrate adjustment and replaces audio quality policy settings and registry configuration requirements. With adaptive audio, customers receive low-latency, DVD-quality audio delivery when network bandwidth allows (and it continuously adjusts as conditions change to provide the best quality given the current situation).
To provide a visual comparison, we captured a high-fidelity audio sample and created these graphs showing the before and after.
The spectral representation of the audio, from the lowest bass frequencies to the highest tone pitches, really shows the quality and depth of the audio remoting captured from the actual client hardware device audio output. This breakthrough unlocks many new audio use cases for our customers.
Armed with a new low-latency adaptive audio codec, we also added support for RTP audio transport using UDP audio transport through UDP. With the combination of the adaptive audio codec and UDP audio transport, customers can now deliver a great audio experience through various network condition.
Configuring the New Adaptive Audio Service
For the most part, you don’t have to configure it! Adaptive audio is the new default audio codec starting in Citrix Virtual Apps and Desktops 2109. There’s no policy configuration needed to enable this audio service when Citrix Workspace app for Windows, Mac, and Linux 2109+ is used to connect to the 2109+ VDA. The new audio service will also fall back to the legacy codec when client devices can’t support adaptive audio. This is a truly configuration-free solution for the administrator.
If bi-directional real-time audio redirection in unreliable networks is required, customers can add UDP audio to improve the user experience.
To configure UDP audio transport in local area networks, customers should enable the following policies:
- Audio over UDP = Allowed (open up UDP ports on the VDA)
- Audio over UDP real-time transport = Enabled (enable UDP Audio transport feature on VDA)
- Audio quality = Medium (only needed for CWA client prior to 2109)
- Audio UDP port range= 16500,16509 (Default value)
For external network connections, customers must configure Citrix ADC with DTLS support to encrypt the UDP transport. To configure external access for UDP Audio transport through DTLS:
VDA Policy
HDX Adaptive Transport= Off (This setting will avoid EDT to use UDP transport and reserve UDP DTLS transport to be used by UDP Audio.)
CWA Windows 2112 or Higher Client Configuration for UDP Audio Support
Use the Local Group Policy Editor, go to:
Local Computer Policy → Computer Configuration → Administrative Templates → Citrix Components → Citrix Workspace → User experience → Client audio settings
Select “Enabled” then check “Enable audio,” “enable Real-Time Transport,” and “Allow Real-Time Transport through NetScaler Gateway” to allow UDP transport to be encrypted via DTLS.
Alternatively, admins can edit the Default.ica file to enable UDP Audio for the endpoint.
Open C:\inetpub\wwwroot\Citrix\<Store Name>\App_Data\default.ica with a text editor.
Under [ApplicationServers] section add:
- EnableRtpAudio=true
- EnableUDPThroughGateway=true
- RtpAudioLowestPort=16500
- RtpaudioHighestPort =16509
CWA Linux 2202 or Higher Client Configuration
Under the [ClientAudio] section of module.ini, set the following configuration:
- EnableUDPAudio=true
- UDPAudioPortLow=16500
- UDPAudioPortHigh=16509
Under [WFClient] section set the following config:
- EnableUDPThroughGateway=True
Please note, if you use the StoreFront default.ica configuration, the value of EnableUDPThroughGateway set in the [Application] section takes precedence over the value set in the module.ini file. However, you can set the EnableUDPAudio value in the [ClientAudio] section only using the module.ini file. Also, it does not take precedence over the value set in the StoreFront default.ica configuration.
Citrix Gateway Configuration
In the Citrix Gateway go to Citrix Gateway → Virtual Servers.
Enable DTLS to enable UDP through DTLS encryption support.
Check out our documentation to learn how to configure a DTLS VPN virtual server by using the GUI. Alternatively, you can configure a DTLS virtual server using the XA/XD wizard.
Learn More
To summarize, adaptive audio makes a significant difference in audio quality across all connection types and is now the default in the latest VDA and Citrix Workspace app releases. We encourage you to update your Windows, Mac, and Linux CWA versions to 2109 or higher and enable UDP audio transport when real-time communication software is used inside the VDA to provide the best possible user experience. Let us know your thoughts below, and we look forward to a great sounding 2022 and beyond! To learn more, check out this video:
