This article describes how to configure HDX’s image quality using Extra Color Compression.

Background

This feature was first introduced in XenDesktop 4 Feature Pack 1. Extra Color Compression offers significant bandwidth reductions (approximately 35 percent). This feature is enabled by default. This is ideal for WAN users for reducing bandwidth consumption at the expense of image quality. When delivering Windows 7 desktops to LAN-connected users, it is best to disable Extra Color Compression, to deliver a visually lossless experience.

Instructions

Caution! Refer to the Disclaimer at the end of this article before using Registry Editor.

To disable Extra Color Compression on LAN scenarios, use one of the following registry keys based on the current lossy compression setting. If the current lossy compression setting is Low Compression; best image quality as set in the Image Acceleration Policy then EnableSubamplingOnHighQuality could be set to 0 to disable the Extra Color Compression and get even better visual quality.

By default, the lossy compression setting is Medium Compression; Good Image Quality.

• HKEY_LOCAL_MACHINE\Software\Citrix\PortICA\Thinwire\EnableSubsamplingOnHighQuality

  Data type: REG_DWORD

  Value data: [0,1] Default 1

• HKEY_LOCAL_MACHINE\Software\Citrix\PortICA\Thinwire\EnableSubsamplingOnMediumQuality

  Data type: REG_DWORD

  Value data: [0,1] Default 1

• HKEY_LOCAL_MACHINE\Software\Citrix\PortICA\Thinwire\EnableSubsamplingOnLowQuality

  Data type: REG_DWORD

  Value data: [0,1] Default 1

On 64-bit systems, these registry keys exist under Wow6432Node.

HDX Policy settings are used to set HDX Image settings in XenDesktop 5.x. Refer to the online documentation for XenDesktop for details.