Re: [Denemo-devel] fluidsynth

[Richard Shann]

I've pushed a small fix in fluid.c
Richard

On Sun, 2009-11-01 at 20:12 +0000, Richard Shann wrote:
> ... and I have now fixed the memory leak, as you can switch movements
> etc while playing back with fluidsynth or external player without a
> crash.
> Richard
> 
> On Sun, 2009-11-01 at 20:05 +0000, Richard Shann wrote:
> > I have put in the check for si->smf being NULL when the callback
> > happens.
> > Richard
> > 
> > On Sun, 2009-11-01 at 16:14 +0000, Richard Shann wrote:
> > > I have merged in some changes to the fluidsynth work as it was not
> > > building with fluidsynth disabled. This led me into looking at the new
> > > code and I want to make some comments, the first of which is to say how
> > > glad I am to see this work progressing.
> > > There are three issues I have noticed
> > >       * There was a serious memory leak (sorry, my fault), which I
> > >         noticed because your code did not crash when deleting the score
> > >         currently being played. I was expecting it to do so, because you
> > >         have introduced a dangling pointer. I have fixed the memory
> > >         leak, but surrounded it with #ifdef  DANGLING_SMF_POINTER_FIXED
> > >         since it cannot be fixed without fixing the dangling pointer.
> > >         More detail below.
> > >       * There is the problem which you already have noted in a comment
> > >         in fluid.c (trying to use the fluidsynth structure for a midi
> > >         event). The structure is opaque and would need access via
> > >         function calls to set its values.
> > >       * You have included an extra timer which is needlessly complex.
> > >         Instead of tracking ticks with g_timeout_add(2,
> > >         tick_timer_callback, NULL); you should consult the time in the
> > >         idle callback and decide whether or not to output the midi event
> > >         directly there. That is, whenever the idle callback fires, look
> > >         at the next event(s) and output them if it is time.
> > > 
> > > The important one is the dangling pointer. This is introduced by the
> > > line:
> > > 
> > >   smf = Denemo.gui->si->smf;
> > > 
> > > there is no means of ensuring this value is not used after the memory it
> > > points to has been freed. Instead, in the callback refer to
> > > Denemo.gui->si->smf itself, checking that it is not NULL. If it is NULL,
> > > then stop the playback and remove the idle callback.
> > > 
> > > This would mean that if someone changed movements or deleted something
> > > etc, the idle callback would carry on playing the new movement from
> > > wherever it had been left. We could, of course, take measures to turn
> > > off the playback when that happens, but the main point is we don't have
> > > to in order to keep the program structurally sound: the playback will
> > > never attempt to play freed memory.
> > > 
> > > The second bullet point above needs more digging in the fluidsynth docs,
> > > it looks like we *could* move to using fluidsynth in place of libsmf, it
> > > would give smoother integration. However, I would be nervous of putting
> > > our eggs in that basket too early, and it would require a whole chunk
> > > more work. For now, perhaps it we can create the fluidsynth midi event
> > > from the smf midi event without too much pain; if not we can write a
> > > switch like the one I paste below, taken from their code for the midi
> > > handle function.
> > > Richard
> > > fluidsynth code:
> > > switch(type) {
> > > 03158       case NOTE_ON:
> > > 03159         return fluid_synth_noteon(synth, chan,
> > > 03160                                  fluid_midi_event_get_key(event),
> > > 03161                                  
> > > fluid_midi_event_get_velocity(event));
> > > 03162 
> > > 03163       case NOTE_OFF:
> > > 03164         return fluid_synth_noteoff(synth, chan, 
> > > fluid_midi_event_get_key(event));
> > > 03165 
> > > 03166       case CONTROL_CHANGE:
> > > 03167         return fluid_synth_cc(synth, chan,
> > > 03168                              fluid_midi_event_get_control(event),
> > > 03169                              fluid_midi_event_get_value(event));
> > > 03170 
> > > 03171       case PROGRAM_CHANGE:
> > > 03172         return fluid_synth_program_change(synth, chan, 
> > > fluid_midi_event_get_program(event));
> > > 03173 
> > > 03174       case CHANNEL_PRESSURE:
> > > 03175       return fluid_synth_channel_pressure(synth, chan, 
> > > fluid_midi_event_get_program(event));
> > > 03176 
> > > 03177       case PITCH_BEND:
> > > 03178         return fluid_synth_pitch_bend(synth, chan, 
> > > fluid_midi_event_get_pitch(event));
> > > 03179 
> > > 03180       case MIDI_SYSTEM_RESET:
> > > 03181         return fluid_synth_system_reset(synth);
> > > 03182   }
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > _______________________________________________
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> > > http://lists.gnu.org/mailman/listinfo/denemo-devel
> > 
> > 
> > 
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