Improving the VNC connection performance

Queries related to T-Plan Robot
Post Reply
Posts: 74
Joined: Thu Oct 29, 2009 5:43 pm
First Name: Robert
Last Name: Pes
Company: T-Plan

Improving the VNC connection performance

Post by rpes » Wed Oct 20, 2010 7:33 am

A question from the support:
My VNC connection is too slow. How do I improve it?
VNC performance can be fine tuned through settings both of the client (Robot) and server. On the Robot side select Edit->Preferences in the GUI and locate the "RFB (VNC) v3.3 Client" tree node in the Plugins tree branch. The screen will display a list of encodings. The default setting with RRE and Raw in the first place (shown on the picture below) is the most conservative and also the slowest one but it is compatible across many VNC products (including VNCs on mobile devices). If you move the Zlib or Hextile encoding to the first place, you should see an improvement in performance because these encodings compress the transferred image data.


The performance may be further on increased by switching to a lower color depth to 16bit (65k colors) or even 8bit (256 colors). This can be done through the Pixel Format setting in the screen. As this greatly reduces the volume of image data, it usually leads to a significant improvement. Be just aware that template images are not compatible across different color depths and need to be recreated on any such a change.

On the VNC server side the performance may be increased through smaller screen resolution and eventual tweaking of server specific settings. Resolution change makes the biggest difference. An important fact to realize is that a 1280x1024 screen contains about 67% more pixels than a 1024x768 one and this data needs to be pushed and maintained through the VNC connection.

If none of the settings above improve performance of your VNC connection, the problem is in your network speed. As VNC works over TCP/IP, it can be only as fast as your network is.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest