Re: [Denemo-devel] What is the duration of a measure

[Richard Shann]

Thanks for this - it sounds like you have all the pieces to hand - I'll
try to get to it, unless you tell me you are connecting them all up for
me!
Richard

On Tue, 2009-09-22 at 08:56 -0500, Jeremiah Benham wrote:
> On Tue, 2009-09-22 at 09:07 +0100, Richard Shann wrote:
> > Jeremiah
> > Do you know if we have a function to get the duration of a whole measure
> > given the time signature?
> > I am trying to improve the whole measure rest thing, I can do that if I
> > can transform
> >     4/4         -->   r1
> >     12/8        -->   r1.
> 
> I started witting something like that in importmidi.c  In midi there is
> a value called ppqn. This stands for Pulses Per Quarter Note. Usually
> this value is set to 384. To find out how many pulses are in a measure
> you do this:
> 
> gint barlength = ppqn * 4 * numerator / denominator;
> 
> numerator and denominator refer to the time signature.
> 
> Then in importmidi.c line 776. There is this:
> 
> while(mididata->barlength - mididata->bartime){
>         rest = mididata->barlength - mididata->bartime;
>         struct notetype length = ConvertLength(rest, mididata);
>         new_dnm_object(mididata, mididata->currentnote, length, FALSE);
>         mididata->bartime += ConvertNoteType2ticks(mididata, &length);
>         mididata->lastoff += ConvertNoteType2ticks(mididata, &length);
>       }
> 
> and lines 786-791:
> 
> 
> if (rest){
>         struct notetype length = ConvertLength(rest, mididata);
>         new_dnm_object(mididata, mididata->currentnote, length, FALSE);
>         mididata->bartime = mididata->bartime +
> ConvertNoteType2ticks(mididata, &length);
>         mididata->lastoff += ConvertNoteType2ticks(mididata, &length);
>         rest = 0;
> 
> 
> So now you need the function ConvertLength:
> 
> notetype ConvertLength(gint duration, midicallback *mididata){
>  /*convert length to 2 = quarter, 1 = half, 0 = whole etc...... */
>         /* quarter = 384, half = 768, whole = 1536*/
>   notetype gnotetype;
>   gint PPQN = mididata->smf->ppqn;
>   gint notetype = 0;
>   gint numofdots = 0;
>   gint tied = 0;
>   gint leftover = 0;
>   gint dsq = (4 * PPQN);
> 
> 
>   while ((dsq >> notetype) > duration)
>           notetype++;
> 
>   leftover = duration - (dsq >> notetype);
> 
>   while (leftover >= (dsq >> (notetype +1))){
>         leftover -= (dsq >> (notetype +1));
>         numofdots++;
>   }
> 
>   gnotetype.notetype =
> notetype;                                          
>   gnotetype.numofdots = numofdots;
>   gnotetype.tied = leftover;
>   return gnotetype;
> }
> 
> 
> ConvertLength converts ticks to a notetype. I also have this function if
> you need to go the other way around:
> 
> ConvertNoteType2ticks(midicallback *mididata, notetype *gnotetype){
>   gint ticks;
>   gint PPQN = mididata->smf->ppqn;
>   gint notetype = (int) gnotetype->notetype;
>   gint numofdots = (int) gnotetype->numofdots;
>   gint dsq = (4 * PPQN);
>   gint i = 0;
> 
>   ticks = dsq >> notetype;
>   while (i++ < numofdots)
>     ticks += dsq >> notetype + 1;
> 
>   return ticks;
> }
> 
> 
> IHTH,
> Jeremiah
> 
> 
> > and so on
> > (hmm, for all possible keysigs? it would mean 
> > 
> > 5/8 --> r2 r8
> > 
> > or anything equivalent but I don't personally need this)
> > 
> > My question is about Denemo internals really - is there some conversion
> > from keysignature to whole measure length that you have come across
> > doing the stuff you have done so far?
> > Richard
> > 
> > 
> > 
> > 
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>