Hello Alexander, Your findings are correct :) With the only exception: Screenshots are taken in single thread, so there are some limitations in the speed :( I believe Thread.sleep(xxx) doesn't work at all I'm planning to rewrite this part And hopefully will be able to increase FPS.
Basic compilation steps are here: http://openmeetings.apache.org/BuildInstructions.html After compiling all jars in screensharing folders are being signed, so you need to replace all of them, otherwise you will get security error due to different certificates On Thu, Oct 24, 2013 at 3:07 AM, Alexander Brovman < alexander.brov...@gmail.com> wrote: > Hi, > > I have two quick questions, but first of all i just wanted to say that > Openmeetings is fantastic. I had both OpenMeetings and BBB Installed and we > have decided to go with OM. > > I am relatively apt at programming with Python and C# but I have never > worked with a lot of Javaapplications like these ones, so i have the > following questions: > > *1)* From what i understand the ScreenSharing is performed by taking > snapshots every x milliseconds. Additionally there is an algorithm in place > that divides the snapshot into tiles and measures the changes in tiles, if > there is a change the tile is uploaded. If this is correct, and i want a > more.. "fluid" video because there will be a lot of changes, cant i simply > modify the "framerate" at which the images will be compared to improve the > output? I am well aware that this would eat into the CPU and the bandwidth > but i have a Full Duplex Gbit and 2x Quadcore Xeons available to me so this > is not an issue. We are trying to test for an extreme case of 500-1500 > users and how to optimize the output, i think the developers and other > users will be interested in seeing the results. > > > *2)* Where would these changes need to be made? So far i have isolated > the CoreScreen.java , CaptureScreen.java and theScreenV1Encoder.java files > that apparently contain the code which processes the desktop sharing. > > The CaptureScreen.Java has the: > "timeBetweenFrames = (ScreenDimensions.quality == ScreenQuality.VeryHigh) > ? 100 : 500;" setting on line 54 which basically says that if Screequality > is set to very high (condition is true) then select 100 as the value for > timeBetweenFrames. > > This variable is apparently used lateron in the "Thread.sleep(Math.max(0, > timeBetweenFrames - spent));" on line 96, which will pause the current loop > for the amountof time that is the difference between timeBetweenFrames( in > our case 100ms) minus the spent time (which is defined on line 91). > > So in Theory if i wanted to output the screen in realtime at 20 or 24 > frames per second which would mean that a snapshot would need to be taken > every 50 milliseconds or so, would i simply need to set a different frame > setting for the time between frames, something like: > "timeBetweenFrames = (ScreenDimensions.quality == ScreenQuality.VeryHigh) > ? *20* : 500;" > > Reduce the Thread.sleep(60); on line 60 to something like 20 milliseconds > so (Thread.sleep(20);) > and then finally remove the the last part "Thread.sleep(Math.max(0, > timeBetweenFrames - spent));" or perhaps leaving it in? > > I understand that this would be a .. "wrench and hammer" approach since > this will probably eat up quite a bit of CPU usage. I mean the simpler > solution here clearly would be to get rid of the algorithm itself and > simply rewrite it to simply output a screenshot every x milliseconds or so, > but i have no idea how deep i would be messing with openmeetings and if > that would/could break other parts of openmeeting that access these files? > > So would this be a workable solution that i could at least try out? I > would ofcourse be more than happy to supply the CPU Usage differences. > > *3)* My only question would be is how would i recompile these? I am > asking because i read somewhere in the mailinglists (or the old google > groups) that it is recommended to use ANT in order to recompile things. > Also what will be the output name of the .jar that is essentially being > loaded for people and located on the server? > Because all i can find on my Debian box is > the > /usr/lib/red5/webapps/openmeetings/screensharing/openmeetings-screenshare-2.1.1-RELEASE.jar > file. > > So yeah, if somebody could help me with recompiling i would appreciate it! > :) > -- WBR Maxim aka solomax
