Use the Server Configuration console Acceleration tab

The Acceleration tab provides options to change the Acceleration or Quality level and disable dynamic compression.

When the Override client acceleration/quality settings check box is selected, all sessions use the configured setting, and all client settings are ignored. When selecting or clearing this setting, the service must be restarted for the change to become effective. When the setting is enabled, changing the acceleration level does not require a service restart, but active users must reconnect to use the new setting.

Dynamic Compression identifies small graphic elements within an application screen and compresses them during runtime. The most compression occurs when image quality is set to Low. The best quality images occur when image quality is set to higher than Low. All other graphical objects are compressed at the selected quality. This provides the visual impression of a high quality remote desktop session.

By default, this feature is enabled. To disable dynamic compression, clear the Use dynamic compression box.