The impact of graphics card temporal dithering
Temporal dithering is an intentionally applied blurring method used by some graphics cards to increase the amount of color and shading that can be done on a system. It's a trade-off between a little distortion and much smoother looking pictures.
During PCoIP remote sessions, temporal dithering forces even static images to be dynamic to emulate a color that is not available in its color palette by constantly switching between two nearby colors very quickly. The effect is not perceptible to the human eye, but results in a significant overhead for any compression algorithm, such as that used by PCoIP, when dealing with the increased pixel color activity. Every time a pixel gets updated, the host updates that information to the client through the network.
The following are some symptoms and/or effects of temporal dithering:
- High frame rate and bandwidth utilization during a session with minimal or no screen changes
- PCoIP Zero Client logs might contain -500 MGMT_IMG :(pkt_rx_resource_check): Insufficient imaging resources. Dropping imaging data.-
- PCoIP Remote Workstation Card logs might contain DESC :Out of buffer! DESC :Out of buffer!
To correct a problem caused by temporal dithering, you can do either of the following:
- Use a graphics card that does not support dithering. Note that a graphics card with dithering enabled on one operating system may not have dithering enabled on other operating systems because of the various driver versions. Consult your graphics card documentation or contact your card vendor for more information.
- Disable the temporal dithering option of your graphics card through its driver.
- Ensure the color depth is set to 8-bit color per pixel.
- Windows is set to a color depth of 32-bit
- If you are using HP Anyware on a vGPU platform equipped with NVidia GRID GPUs, such vGPU optimized graphics cards do not have the temporal dithering feature since there is physical monitors attached to a vGPU. Therefore you will not be impacted by the ill effects of the temporal dithering.
- PCoIP only supports 8 bit color per a pixel. Ensure all GPU and Windows settings match this setting.
- Latest version of PCoIP Software Client and Zero Client firmware modify the EDID of the attached display to report 8-bit color depth.