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List:       kde-multimedia
Subject:    Re: PlayObject changes
From:       Achim Bohnet <ach () mpe ! mpg ! de>
Date:       2000-07-17 23:48:51
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>>>Stefan Westerfeld wrote:
 >    Hi!
 > 
 > I've made a few changes to PlayObject today. Like always, changing interfaces
 > is binary incompatible. So please if there are any remaining issues, or you'd
 > like to have it different, bring them up soon, as we won't be able to change
 > these issues later (especially not after the KDE2.0 release).

Not a playobject issue, and if  AudioSubSystem is internal (== not affected
by binary compatibility requirement ) it's not a problem at all:

The suspend/resume feature let other
program use /dev/dsp.   But in the case a given audiosubsys implementation
not use /dev/dsp (e.g., NAS, /dev/dsp{0,1}, or alsa(?)) there's no need for
a open/close.  So it would make sense to add

  int AudioSubSystem::suspend(void) { return close(); }
  int AudioSubSystem::resume(void) { return open(fullDuplex()); }

or a 

  bool AudioSubSystem::suspendMakesSense() { return };

to the audiosubsystem.


Achim
 > 
 > 1. Changed posFinished to posIdle:
 > 
 >  enum poState {
 > +  posIdle,
 >    posPlaying,
 > -  posFinished,
 >    posPaused
 >  };                                                                             
 > 
 > A PlayObject is supposed to start up IDLE now (not PAUSED). Then, if the user
 > pushes play, the PlayObject is supposed to get PLAYING, until it has played
 > everything (i.e. Song done), then it is going IDLE again.
 > 
 > You can force a PlayObject to go IDLE anytime using a new method called halt(),
 > this should also seek back to the beginning, see below. If you use pause(),
 > the PlayObject will be PAUSED, and if you do play() again, it will be PLAYING
 > again. Well, I hope this is a logic choice of states now.
 > 
 > 2. The halt() method:
 > 
 > +   /**
 > +     * stop playing the media. Normally this function would called stop,
 > +     * but the name is reserved for the start/stop mechanism of the
 > +     * aRts objects.
 > +     */
 > +    void halt();
 >  };                                                                             
 > 
 > Usually, this method would be called stop(), but well, aRts already uses
 > start() and stop() for other things (streaming object starting/stopping),
 > so this was the second best choice.
 > 
 > Note: there was no stop before, because we said: well, you can always stop
 > it by using playObject = Arts::PlayObject::null(), which will cause its
 > reference count to drop and the PlayObject to go away. But for the user
 > interface it seems more convenient/logic to call halt() whenever the user
 > pushes the stop button, than terminating the PlayObject.
 > 
 > 3. Making more attibutes readonly:
 > 
 > -    attribute string description;
 > -    attribute poTime currentTime;
 > +    readonly attribute string description;
 > +    readonly attribute poTime currentTime;                                     
 > 
 > While it would make sense to set currentTime (i.e. seek), we have an explicit
 > seek already, which is maybe more understandable. We needed to get rid of one
 > and I choose setting currentTime as less intuitive.
 > 
 > On the other hand, the PlayObject should know it's description (i.e. ID3
 > Tag), and setting this is not what you'll usually be able to do. Hmm, this
 > might be discussable, but I removed it for now, unless there are any strong
 > objections.
 > 
 >  * * *
 > 
 > If you would like to have anything done different, now is the chance to say
 > it ;)
 > 
 > Also, please Martin and Charles, look into your sources and see that I didn't
 > break anything essential... especially halt() is probably unused/unimplemented,
 > and the mpeglib PlayObjects may come up paused (instead of idle). The wave
 > PlayObject in kdelibs should be okay.
 > 
 >    Cu... Stefan
 > -- 
 >   -* Stefan Westerfeld, stefan@space.twc.de (PGP!), Hamburg/Germany
 >      KDE Developer, project infos at http://space.twc.de/~stefan/kde *-         
 > _______________________________________________
 > Kde-multimedia mailing list
 > Kde-multimedia@master.kde.org
 > http://master.kde.org/mailman/listinfo/kde-multimedia



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