Linux: Screen desktop video capture over network, and VNC framerate

Question

Sorry for the wall of text - TL;DR:

• What is the framerate of VNC connection (in frames/sec) - or rather, who determines it: client or server?
• Any other s

Answer 1

You should get a badge for such a long well though out question. ;-)

In answer to your primary question, VNC uses the RFB protocol which is a remote frame buffer protocol (thus the acronym) not a streaming video protocol. The VNC client sends a FrameBufferUpdateRequest message to the server which contains a viewport region that the client is interested in and an incremental flag. If the incremental flag is not set then the server will respond with a FrameBufferUpdate message that contains the content of the region requested. If the incremental flag is set then the server may respond with a FrameBufferUpdate message that contains whatever parts of the region requested that have changed since the last time the client was sent that region.

The definition of how requests and updates interact is not crisply defined. The server won't necessarily respond to every request with an update if nothing has changed. If the server has multiple requests queued from the client it is also allowed to send a single update in response. In addition, the client really needs to be able to respond to an asynchronous update message from the server (not in response to a request) otherwise the client will fall out of sync (because RFB is not a framed protocol).

Often clients are simply implemented to send incremental update requests for the entire frame buffer viewport at a periodic interval and handle any server update messages as they arrive (i.e. no attempt is made to tie requests and updates together).

Here is a description of FrameBufferUpdateRequest messages.