A question about the bandwidth.

  • Nobody/Anonymous

    How much bandwidth is needed if 10 people in a conference with a/v and desktop sharing?
    Is there any formula to calculate the bandwidth needed in the server side?
    I think the desktop sharing eat a lot bandwidth,so i'm curious how many attendees can see the Presenter's desktop.


    • Rajesh Dharmalingam


      Thanks for using Dimdim. Basically, each person who are starting or joining the conference requires a minimum of 150Kbps. So, who ever starts or joining the meeting requires a bandwidth of 150Kbps in terms of both upload and download speed.

      Regarding the desktop sharing, the delay can be reduced by configuring the "Settings" from the presenter who started the meeting. Based on the "Network Setting:" and "Image Quality:" from Settings of presenter, the delay can be reduced. Try configuring both to low and let me know if you are facing the issue,

      If you are facing any issues, please do mail me at rajesh(@)dimdim.com.


    • Nobody/Anonymous

      I read "Bandwidth Requirement" in the installation guide and confused.
      Take the broadband condition as example.
      Max upload bandwidth = 150~200kbps
      Then I calculate the bandwidth required according to the settings followed.
      The bandwidth for desktop sharing is
      1024*768*8bit(256 color depth)*10%(screen change)*1fps = 629k/s much more then 150~200k/s
      The bandwidth for video sharing is
      160*112*5fps= 89.6k/s not 38kps

      Am i wrong?Could you please explain this?
      Thanks you very much!

    • Rajesh Dharmalingam

      Thanks for the updates. For screen share, we use the Screen Video codec (version 1). As part of this, we compress the screen that we capture. The screen is first quantized (or alternately converted to 8-bit colors like you have mentioned).
                  This process makes compression very effective. This is for the first update that we send. In this, we also make further improvements by sending "bands" of data instead of a single screen. This is why you see that your page updates sequentially from top left to bottom right of the screen. This means that each packet is even smaller. And for further updates, like you have mentioned, we only send changes compared to the previous screen. Since we send out the updates also in bands, each update will have even lesser data since the unchanged part of the screen doesn't even go out.
               We have conducted a few tests with some typical desktops and came to the conclusion that a minimum of 150 kbps will allow screen share and also audio/video to give a reasonable performance

    • Nobody/Anonymous

      Thanks for your reply.According to what you said,the 629k/s considered the screen change but not the compress rate.So it should be 629k/s*n(maybe n=10%)
      //1024*768*8bit(256 color depth)*10%(screen change)*1fps = 629k/s

      Howerver i still can't understand this:
      The bandwidth for video sharing is
      160*112*5fps= 89.6k/s not 38kps 

      Could you explain it please?


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