Using Lawo Virtual Patch Bay to Send PC Audio on an AES67 Stream

Lawo Virtual Patch Bay (VPB) is a powerful tool that can be used to send and receive AES67 streams from your PC. To see installation instructions, and how to receive audio, see

In order to allow VPB to generate SDP files, that may be copied into EHX, make sure to install the latest version,

VPB will sync to your available PTP clock on startup, and you will see the sync icon in the lower right flash yellow, then turn solid blue once it syncs to PTP.

In order to set basic options in VPB, click the Lawo logo in the upper right, and select the “Ravenna” tab. There, you can specify the NIC, PTP parameters, and a default multicast address range:

Settings Dialog


In order to create a transmit stream from your PC, click device-> add → add stream:

A dialog box will appear, and you can name it, select either 2 or 8 channel stream, and set other parameters, including the multicast address. ( Note: Clearcom only accepts multicast addresses in the 239.x.x.x range)


Add Stream Dialog

The new stream will appear along the bottom, default color is olive. ( You can change the color by right clicking. Also, the stream will appear in color when it is active, and be grayed out if not)


In order to set up the stream on a Clearcom IPA card, it’s helpful to have the SDP file available to copy into EHX. Unfortunately, LAWO VPB does not provide this option by default. It can be enabled though, by modifying the R3LAYVirtualPatchBay.ini which can be found in the following directory:


Open the file in a text editor, and add the following 2 lines:



The first few lines of the .ini file will then look something like this:




Save the .ini file, and restart VPB to import the new setting.


You can now right click the stream you just created, and an option for “Copy SDP” will appear:

The SDP file for that stream has been copied to the clipboard, and you can now copy it into the necessary port(s) in EHX in Rx AoIP Device Options.

Lastly, make the necessary crosspoints in VPB to route from your audio driver ( in this case WDM driver 5) to the new stream. If audio is present, the crosspoints will light up green.

Using the routing feature of VPB, you can also route any available audio to and from any endpoint, such as the PC’s mic or speaker, or between different AES67 streams. In the example below, the incoming stream, “ AUS Delta” has been routed to the output stream Relay7:



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