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Thread: very slowly apps

  1. #1
    Join Date
    Oct 2007
    Location
    Poland
    Posts
    17
    Qt products
    Qt4
    Platforms
    Unix/X11 Windows

    Post very slowly apps

    I have problem with QProcess. My code:
    Qt Code:
    1. class Mencoder : public QObject
    2. {
    3. ...
    4. private:
    5. QProcess *proc;
    6. };
    7. ..
    8.  
    9. Mencoder::Mencoder( .../* some parameters */, QObject *parent ) : QObject( parent )
    10. {
    11. proc = new QProcess( this );
    12. connect( proc, SIGNAL( readyReadStandardOutput() ), this, SLOT( update() ) );
    13. connect( proc, SIGNAL( finished(..) ), this, SLOT( on_finished(..) ) );
    14. ...
    15. proc->start( "mencoder", arg );
    16. }
    17.  
    18. void Mencoder::update()
    19. {
    20. ......
    21. emit newInfo( .... /*some new data for main apps*/ );
    22. }
    23.  
    24. void Mencoder::on_finished(..)
    25. {
    26. ..
    27. proc->close();
    28. deleteLater();
    29. }
    To copy to clipboard, switch view to plain text mode 

    Everything works, but i have problem with cpu usage. From system info i have this:
    %CPU COMMAND
    32 mencoder
    40 myApps
    23 xorg
    Wher's the problem?

  2. #2
    Join Date
    Jan 2008
    Posts
    2
    Qt products
    Qt3 Qt4
    Platforms
    Unix/X11 Windows

    Default Re: very slowly apps

    i assume mencoder is outputting to fast or is updating a percentage or remaining time or something like that
    in this case i would delay emit newInfo(), so it would be emitted max every 50 msecs or something like that

    maybe it helps, just a thought

  3. #3
    Join Date
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    Default Re: very slowly apps

    Qt Code:
    1. connect( proc, SIGNAL( readyReadStandardOutput() ), this, SLOT( update() ) );
    To copy to clipboard, switch view to plain text mode 
    You are updating the display every time there is something to read from the process. That's not a very good thing to do, regardless of what you do within update (especially that your paintEvent() is probably not very well designed).

    I never had problems with mencoder and cpu usage of the frontend.

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