MIDITempo.cxx

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/*
 * Copyright (c) 2001-2004 MUSIC TECHNOLOGY GROUP (MTG)
 * UNIVERSITAT POMPEU FABRA
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * MIDIFileReader C++ classes
 * This code is part of the CLAM library, but also usable stand-alone.
 * Maarten de Boer <mdeboer@iua.upf.es>
 *
 */
#include "MIDITrack.hxx"
#include "MIDISong.hxx"
#include "MIDITempo.hxx"
#include "Defines.hxx"

namespace MIDI
{

        class TempoImpl
        /* hidden implementation of class Tempo */
        {
        friend class Tempo;
        private:
                Song* mSong;
                Track* mTrack;
                Track::EventIterator mIterator;
                int mUsPerQ; // microseconds per quarternote
                bool mHasTempo;
                
                /* while iterating through the tempo events, we need to keep track of
                ** the time, by applying all the tempo changes and calculation the 
                ** time increment. these two vars are used in the process
                */
                int mLastTicks; 
                int mLastTime;
                
                TempoImpl(Song* song = 0,Track* track = 0)
                {
                        Init(song,track);
                }
                
                void Init(Song* song = 0,Track* track = 0)
                {
                        mHasTempo=false;
                        mSong = song;
                        mTrack = track;
                        if (mSong && mTrack==0)
                        {
                                for (int i=0;i<mSong->Tracks();i++)
                                {
                                        Track* t = mSong->GetTrack(i);
                                        if (t->HasTempoEvents())
                                        {
                                                mTrack = t;
                                                break;
                                        }
                                }
                        }
                        if (mTrack)
                        {
                                mHasTempo=true;
                                mIterator = mTrack->Begin();
                        }
                        mUsPerQ = 500000;
                        mLastTime = 0;
                        mLastTicks = 0;
                }

                Milliseconds TicksToTime(Ticks t)
                {
                        if(!mHasTempo)
                        {
                                // return time based on tempo = 120 bpm because the track has not tempo events
                                return (Milliseconds)((double)t*480.0/(double)mSong->GetTicksPerQ());
                        }

                        int i = 0;

                        /* move the iterator to the next tempo event */
                        while (mIterator!=mTrack->End())
                        {
                                const Event &ev = **mIterator;
                                if ( ev[0]==0xFF && ev[1]==0x51)
                                {
                                        break;
                                }
                                mIterator++;
                        }

                        /* if we are at the end of the tempo track, or we are at a tempo 
                        ** event _after_ Ticks t, then we start from the beginning
                        */
                        if (mIterator==mTrack->End() || ((*mIterator)->GetTicks()>t))
                        {
                                mIterator = mTrack->Begin();
                                mUsPerQ = 500000;
                                mLastTime = 0;
                                mLastTicks = 0;
                        }

                        std::list<Event*>::const_iterator prevIterator = mIterator;


                        /* look for the first tempo event after Ticks t, and adjust
                        ** mLastTime and mLastTicks while doing this
                        */
                        while (mIterator!=mTrack->End())
                        {
                                const Event &ev = **mIterator;
                                if ( ev[0]==0xFF && ev[1]==0x51 )
                                {
                                        if (ev.GetTicks()>t)
                                        {
                                                break;
                                        }

                                        MetaEvent* ev = (MetaEvent*) *mIterator;

                                        // the following is to say: 
                                        // (ticks/ticksPerQ)*msPerQ
                                        // but we change the order to stay with integers
                                        mLastTime += 
                                                ( (TInt64(ev->GetTicks() - mLastTicks) * TInt64(mUsPerQ)) / 
                                                        (TInt64(mSong->GetTicksPerQ())*TInt64(1000)) );

                                        mUsPerQ = 
                                                (ev->mData[0]<<16) | 
                                                (ev->mData[1]<<8) |
                                                (ev->mData[0]);

                                        mLastTicks = ev->GetTicks();

                                        prevIterator = mIterator;
                                }
                                mIterator++;
                                i++;
                        }

                        /* move one back, to the event before or at Ticks t */
                        mIterator = prevIterator;

                        // the following is to say: 
                        // (ticks/ticksPerQ)*msPerQ
                        // but we change the order to stay with integers
                        return mLastTime + Milliseconds(
                                        (TInt64(t - mLastTicks) * TInt64(mUsPerQ)) / 
                                        (TInt64(mSong->GetTicksPerQ())*TInt64(1000))); 
                }
        };

        Tempo::Tempo(Song* song,Track* track)
        {
                mImpl = new TempoImpl(song,track);
        }

        Tempo::~Tempo()
        {
                delete mImpl;
        }

        void Tempo::Init(Song* song,Track* track)
        {
                mImpl->Init(song,track);
        }
        
        Milliseconds Tempo::TicksToTime(Ticks t)
        {
                return mImpl->TicksToTime(t);
        }
        
};

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