The VMware Blast ADMX template file (vdm_blast.admx) contains policy settings for the VMware Blast display protocol. After the policy is applied, the settings are stored in the registry key HKLM\Software\Policies\VMware, Inc.\VMware Blast\config.

These settings apply to HTML Access and all Horizon Client platforms.

Table 1. VMware Blast Policy Settings
Setting Description
Audio playback Specifies whether audio playback is enabled for remote desktops. This setting is to enable audio playback.
Blast Codec Quality The minimum and maximum values of the Quantization Parameter (QP) control the image quality of the remoted display when using Blast Codec compression. The QP values range [1-8] and roughly map to the JPEG quality value in the range [20-88]. This quantization applies to non-text regions and has no bearing on text compression.

The maximum QP is mapped to the low JPEG quality configuration and a value of zero for maximum QP results in overriding the configuration by the low JPEG quality configuration.

The minimum QP is mapped to the high JPEG quality configuration and a value of zero for minimum QP results in overriding the configuration by the high JPEG quality configuration.

Cookie Cleanup Interval Determines how often, in milliseconds, cookies associated with inactive sessions are deleted. The default is 100 ms.
Cursor warping When this setting is enabled, the cursor warping feature is enabled. When enabled and the mouse is in absolute mode, the remote agent detects sudden cursor movements and reflects them to the client by moving the local cursor. If this setting is not enabled, sudden cursor movements in the remote agent will be ignored by the client. This setting is disabled by default.
DSCP Marking When enabled or not configured, this setting allows Differentiated Services Code Point (DSCP) values to be established in outgoing Blast network traffic, as specified by the various individual settings for each network hop. When disabled, DSCP values are not established in Blast network traffic.

When enabled, you can set a numeric value in the range 0-63 for the following network connections:

  • DSCP from Agent, TCP/IPv4
  • DSCP from Agent, TCP/IPv6
  • DSCP from Agent, UDP/IPv4
  • DSCP from Agent, UDP/IPv6
  • DSCP from BSG to Client, TCP/IPv4
  • DSCP from BSG to Client, TCP/IPv6
  • DSCP from BSG to Client, UDP/IPv4
  • DSCP from BSG to Client, UDP/IPv6
  • DSCP from BSG to Agent, TCP/IPv4
  • DSCP from BSG to Agent, TCP/IPv6
  • DSCP from BSG to Agent, UDP/IPv4
  • DSCP from BSG to Agent, UDP/IPv6
  • DSCP from Client, TCP/IPv4
  • DSCP from Client, TCP/IPv6
  • DSCP from Client, UDP/IPv4
  • DSCP from Client, UDP/IPv6
H264 Specifies whether to use H.264 encoding or JPEG/PNG encoding. The default is to use H.264 encoding.
H264 High Color Accuracy Increases color accuracy when using H.264 encoding by using the YUV 4:4:4 colorspace instead of 4:2:0.

This setting might result in degraded performance at very high resolutions or with multiple monitors.

H.264 Quality Specifies the image quality for the remote display configured to use H.264 encoding. You can specify the minimum and maximum quantization values that determine how much an image is controlled for lossless compression. You can specify a minimum quantization value for the best image quality. You can specify a maximum quantization value for the lowest image quality. You can specify the following settings:
  • H264maxQP (available range of values: 0-51, default: 36)
  • H264minQP (available range of values: 0-51, default: 10)

For the best image quality, set the quantization parameter (QP) values to within +5 or -5 of the available range of values. These parameters determine the amount of data that is discarded, so a lower value results in higher image quality.

HEVC High Color Accuracy Enable this setting to request increased color accuracy by using the YUV 4:4:4 colorspace instead of 4:2:0 with HEVC encoding. The client requires hardware HEVC 4:4:4 support for this policy to take effect. This setting is enabled by default.
HEVC Enable or do not configure this setting to allow HEVC encoding for remoting the desktop. Disable this setting to use H.264 or JPEG/PNG for encoding.
HTTP Service Specifies the port that is used for secure communication (HTTPS) between the security server or Access Point appliance and a desktop. The firewall must be configured to have this port open. The default is 22443.
Image Quality Specifies the image quality of the remote display. You can specify two low-quality settings, two high-quality settings, and a mid-quality setting. The low-quality settings are for areas of the screen that change often, for example, when scrolling occurs. The high-quality settings are for areas of the screen that are more static, resulting in a better image quality. You can specify the following settings:
  • Low JPEG Quality (available range of values: 10 - 100, default: 25)
  • Mid JPEG Quality (available range of values: 10- 100, default: 35)
  • High JPEG Quality (available range of values: 10 - 100, default: 90)
Keyboard locale synchronization Specifies whether to synchronize a client's keyboard locale list and default keyboard locale to the remote desktop or application. If this setting is enabled, synchronization occurs. This setting applies to Horizon Agent only.
Max Frame Rate Specifies the maximum rate of screen updates. Use this setting to manage the average bandwidth that users consume. The default is 30 updates per second.
Max Session Bandwidth Specifies the maximum bandwidth, in kilobits per second (kbps), for a VMware Blast session. The bandwidth includes all imaging, audio, virtual channel, USB, and VMware Blast control traffic. The default is 1 Gbps.
Max Session Bandwidth kbit/s Megapixel Slope Specifies the maximum bandwidth slope, in kilobits per second (kbps), that is reserved for a VMware Blast session. The minimum value is 100. The maximum value is 100000. The default value is 6200.
Min Session Bandwidth Specifies the minimum bandwidth, in kilobits per second (kbps), that is reserved for a VMware Blast session. The default is 256 kbps.
PNG If you enable or do not configure this setting, PNG encoding is available for remote sessions. If you disable this setting, only JPEG encoding is used for encoding in JPEG/PNG mode. This policy does not apply when the H.264 encoder is active. This setting is not configured by default.
Screen Blanking Specifies whether to have the desktop VM's console show the actual desktop that the user sees or to show a blank screen when the desktop has an active session. The default is to show a blank screen.
UDP Protocol Specifies whether to use the UDP or the TCP protocol. The default is to use the UDP protocol. The setting takes effect when a user performs a session login-logoff on the Horizon Agent machine on which the registry key exists. This setting does not apply to HTML Access, which always uses the TCP protocol.

Applying VMware Blast Policy Settings

If the following VMware Blast policies change during a client session, Horizon Client detects the change and immediately applies the new setting.

  • H264
  • Audio Playback
  • Max Session Bandwidth
  • Min Session Bandwidth
  • Max Frame Rate
  • Image Quality

For all other VMware Blast policies, Microsoft GPO update rules apply. GPOs can be updated manually or by restarting the Horizon Agent machine. For more information, see the Microsoft documentation.