iChat AV 3 testing

Discussion in 'Mac Apps and Mac App Store' started by FireArse, Jan 30, 2006.

  1. FireArse macrumors 6502a

    Oct 29, 2004
    Hey all.

    For my final year project (Electronic Engineering Degree), I'm working on video conferencing tools. As an avid Apple user - I wanted to bring iChat into play. After spending literally hours searching over the net - there is F*ck all information on iChat.

    I know at least H.263 and H.264 are used. I presume AAC is used. But little else is known about iChat.

    So I want to devise an experiment. At what bitrate will iChat say; "hmmm - we don't have enough bandwidth here - lets move to H.263" or "bugger me, we have some more bandwidth, lets go H.264"

    I plan to test this by seeing the CPU load (H.264 is way more CPU hungry) and trying to vary the bitrate available to iChat to use. Are there any ideas on how to do this (apart from allowing Azureus practically all the bitrate)

    Thats the only way i can think of it.

    Any ideas?


  2. superbovine macrumors 68030


    Nov 7, 2003
    do you want to plot cpu usage and network usage?
  3. FireArse thread starter macrumors 6502a

    Oct 29, 2004
    OS X network throttling or prioritization

    I did that last night. I played with uploading on Azureus - and set it to take 80% of my upload capability.

    Continued with iChat video. Discovered something. iChat surveys the video - and 'knows' how much bandwidth is needed to represent the video. Essentially - when i moved all over the screen, iChat took bandwidth away from Azureus and used it for itself. As soon as I stopped and only moved my lips - Azureus upload speed was allowed in increased again.

    First thing that went through my head was prioritizatation either within my 3Com ADSL router - or within OS X.

    Either way, the CPU usage was between 16-17% with or without bandwidth. maybe a next test would be to run azureus on another computer (therefore finding out whether OS X is doing the throttling)

    grrrr. no where nearer to find out at what kbps iChat moves from H.264 to H.263

    Any ideas?!

  4. superted666 Guest


    Oct 17, 2005
    Also Intrested

    Hi there,
    Im also quite intrested to see what you find, a good site for this resouce is http://discussions.apple.com/forum.jspa?forumID=902

    There are a few very knowledgable people who use that forum.

    I found this command when determining bandwidth usage and debuggin ichat

    Try pasting the Bold Text into Terminal and hitting enter
    /Applications/iChat.app/Contents/MacOS/iChat -errorLogLevel 7

    This will force Terminal to ty and launch iChat and create a log in Terminal.

    if you read through this you can determine bandwidth usage that ichat detects.

    Good luck :)
  5. FireArse thread starter macrumors 6502a

    Oct 29, 2004
    You Legend. Thank-you
  6. superbovine macrumors 68030


    Nov 7, 2003
    those codecs you are using have min cpu specs. This will effect your data.

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