A few moons ago, there was a request from some Spark users in igniterealtime for a desktop screen sharing plugin. I did mention at that point that I had done something in the past using Red5 and a screen-capture webcam called VH Screen Capture Driver and that I would dig it out of my archives and put it into a future release of the Red5 plugin.
I have since discovered that this approach has a few drawbacks. It is not bandwidth efficient, will only work on Windows and although the video driver is free, it is not open source. What we needed was for Flash on the desktop to capture the screen as images, send them to a server and re-assemble them back into a video feed which is then published by Red5. Despite my best efforts, I have since not been able to work out how to do this and if anyone has any tips and clues, please tell me. It will be appreciated.
In the meantime I stumbled on Openmeetings in the Openlaszlo community. It is an online meeting collaboration tool developed by Sebastian Wagner with a number of usefull tools like video, white-board and of course screen-sharing. The video sharing is java-based and does not require any software install other than (the java runtime environment) JRE 1.4+. It uses the same java technique (java.awt.Robot class) as Spark to take a screenshot. It goes one step further by pushing the captured screen shots at a regular interval to a web server using the http upload feature. In the spirit of Open Source and re-useability, I have now decided to use Sebatian's approach and keep the images on the web server and allow multiple clients to view with an auto-refreshing webpage instead of my original intention to convert into a video feed for Red5.
I have added this feature to the latest version (0.0.10) of the Red5 plugin. It includes the server-side image upload support, the viewer webpage and the Openmeeting screen publisher application as a java webstart application. Both publisher and viewer can be accessed from the Spark red5 plugin and JWChat. You select the publisher from the menu to publish your desktop screen and you right click the roster context menu to view the desktop screens of your contacts.
As usual, all feedback is welcome.