Virtual Audio Cable (VAC)
20+ years of experience. Connects audio apps together since 1998.
Virtual Audio Cable (VAC)
20+ years of experience. Connects audio apps together since 1998.
Windows has only a limited audio device support in native Remote Desktop Session (RDS) connection, so Virtual Cable devices may not be accessible via RDS/RDP connections.
If target (remote) system is a workstation (Windows XP, Vista, 7-11), Remote Desktop Session is established as a direct/console session too. A local user, if any, is forcibly logged out and you are logged in instead, having his/her local desktop. To access Virtual Cable devices via MME/DirectSound interfaces and control VAC driver from the Remote Desktop connection, you should specify "Play on remote computer" or "Leave at remote computer" for the "Remote audio" or "Remote computer sound" on the "Local resources" tab in the Remote Desktop connection dialog.
When you request a connection, a simplified form of this dialog is present, containing only computer and user names. To view the "Local resources" tab, expand the dialog by clicking the "Show options" or "Options" item.
If target system is a server (Windows 2003/2008/2012/2016 Server etc.), it creates a separate logon session by default. A local user is not disturbed by a remote connection. Only a default local audio device is redirected to the new session. There is no way to use and control other local audio devices in such connection. To access them, you should connect to a "console" session like workstation systems do. It is possible using mstsc command with the "/console" option. In XP SP3, and Windows 6.x+, the /console option is replaced with /admin.
If the host runs 2003 Server system and there is no "RDP Audio" playback device in a remote session, please check Terminal Services configuration at the server (Start - Services - Control Panel - Administrative Tools - Terminal Services Configuration). At left pane, click Connections, right-click RDP-TCP at right pane and click Properties. Open Client Settings tab and make sure that Audio mapping in Disable the following group is not checked.
In Server 2008 and later server versions of Windows, there is no way to connect to a console session via RDS/RDP. To see local audio devices, you should use desktop sharing software.
See Windows Help for details.
The restrictions above are related only to most popular MME/DirectSound/WASAPI interfaces. Using Kernel Streaming interface, you can access remote WDM audio devices from any session type.
Please note that in most cases there will be no audio signals passed over the network between local and remote computers. Even when you use a KS application that sees Virtual Cable devices, all audio operations are performed on a remote computer, no audio data are transmitted to or from a local computer. It is similar to a situation if you are using VAC on a computer without a hardware audio adapter.
Even if all local audio endpoints (including Virtual Cable ones) are accessible in a Remote Session, Windows behavior can prevent you from keeping audio running after the session is disconnected.
As a kernel-mode driver, VAC may not work in some virtualized environments.
Partial virtualization is enough to run most user-mode software (Web and other network servers, remote desktops, distributed calculations) in a virtualized environment. For user-mode applications, virtualization software maintains several separate environments. But there is only a single system's kernel so in most cases you cannot install a kernel-mode driver like VAC on such environment. The system may warn you, in some cases the installation may be successful, however the driver is not actually loaded.
If the environment is virtualized partially (at user-mode level), you cannot install VAC under it. But if you have full access to the host machine, you can install VAC for the entire host, and then all virtualized environments will be able to use VAC.
In a fully virtualized environment, you have a completely separate OS, with its own kernel, so you can separately install and use VAC on each virtual machine of this type.
Please note that any virtualized environment always has higher internal delays (latency) and introduces higher overhead than the same environment working on real hardware. To ensure that the performance of the environment is sufficient for stable streaming, run latency tests in both host and guest systems.
VAC driver supports up to 32 audio channels. Maximum number of supported channels can be changed in driver parameter section of VAC Control Panel.
Windows (tested up to Windows 11 22H2) correctly supports up to 8 channels only. Increasing the number above 8 may cause system problems. For example, Audio Properties Applet hangs and then crashes if "Levels" tab is opened for a playback endpoint that supports more than 8 channels.
Therefore, default number is set to 8. If you have audio software that supports more than 8 channels, you can try to increase the number as desired, but please be careful.