VMware Horizon By Product Technical Guides

Scanner Redirection in Horizon with View

By Peter Brown, Senior R&D Manager, VMware, London, UK

Over the years, I have worked with many devices that were connected remotely to a virtual desktop infrastructure (VDI) using USB redirection. Scanners are often problematic with USB redirection—scans take a long time to complete or do not complete at all.  Scanner redirection over USB requires a large amount of bandwidth and is sequential, so can be very slow over a latent or lossy network link (such as wifi or a WAN). Solving this problem required a similar solution as for webcam remoting (solved using RTAV).

I am delighted to announce that in our latest release we have added scanner redirection to Horizon with View for use with both VDI desktops and Remote Desktop Session Host (RDSH) applications and desktops. The new scanner redirection functionality in View works by capturing the entire image at the client with the scanning device, compressing the image, and sending that compressed image to the guest in the data center, where the image is presented by a “virtual scanner device” to the application that requested the image capture.

The scanner redirection functionality supports both TWAIN and WIA scanning modes, and allows images to be captured from both scanners and other imaging devices (such as webcams).

Setup for Scanner Redirection

The scanner redirection functionality requires the View Agent from Horizon with View version 6.0.2 or later, and the Windows Horizon Client 3.2 or later. (You will find links to download these at the end of the blog.)

When you install the View Agent component, be sure to select the scanner redirection feature if you want to use it; it is disabled by default. If you are installing the feature onto a server-based OS (Windows Server 2008 R2 or Windows Server 2012 R2) for either VDI desktops or RDSH desktops or applications, then be sure that the Desktop Experience feature (a Microsoft operating system feature) is installed on the server OS first. (This is a prerequisite for installing scanners in a server-based OS.)

Tool-Tray Icon for the User

After a user makes a connection from a compatible Windows Horizon Client to the new View Agent, a new tool-tray application icon appears. The user clicks the icon to reveal the compatible image acquisition devices available for scanning. Figure 1 shows an example of this tool-tray application.

Figure 1: Tool-Tray Icon for Scanner Redirection

If you are using the seamless hosted application functionality of Horizon 6, then when the user launches an application using a compatible Windows Horizon Client (and provided that the View Agent on the RDSH server was installed with the scanner feature), the tool-tray icon is remoted to the client’s native tool tray. The default mode of operation is, however, that “it should just work,” and the seamless hosted application should be able to acquire an image without needing manual intervention. The user may need to adjust the preferences if more than one imaging device is connected to the client machine, and the user wants to select a specific scanner, or if the user wants to adjust the scan resolution, and so on.

If the user connects to a View Agent without the scanner redirection functionality installed, or with a Horizon Client that does not support scanner redirection, then the tool-tray icon will not be visible.

Scanner Redirection Preferences

Scanner Redirection Preferences, available by clicking Preferences from the tool-tray icon, allows further configuration of the scanning process, for example, adjusting the default compression applied to the scanning. This can greatly reduce the bandwidth needed to transmit the image (the compression is applied on the client side before the image is transmitted to the guest), but, of course, the more an image is compressed, the lower the image quality. In addition, in the Scanner Redirection Preferences, options are available to adjust the default image capture device (for example, automatic mode, last-used, or an absolute specified device). See Figure 2.

Figure 2: Sample Preferences That Can Be Adjusted from the Tool-Tray Icon

These preferences can also be adjusted by way of Group Policy options in the guest OS. A new GPO file (available in the Horizon with View GPO Bundle) allows this configuration. See Configuring Scanner Redirection in Setting Up Desktop and Application Pools in View for more information.

Scanner UI Options for the User

Depending on the scan mode and the application, the UI options and the functionality available for scanning differ. Figure 3 shows an example of a scan dialog box.

Figure 3: Scan Dialog Box

Flexibility of Scanner Redirection

The scanner redirection functionality allows the scanner or imaging device to be used either in the View desktop, in an RDSH application session, or even in the local client machine, however, not at the same time! The functionality is also compatible with Real-Time Audio-Video functionality. For example, images can be scanned and captured into a graphics application from a webcam, but not at the same time that the webcam is in use by a conferencing application!

Downloading the Essentials

Links to download the View Agent 6.0.2 and the Horizon Client 3.2 follow:

Note: The Local Mode Horizon Client for Windows does not support scanner redirection.

We are excited to bring this feature to Horizon with View! And we encourage you to send your feedback to the VMware Horizon with View Community Forum. Your feedback helps us make a better product.