JaySynth/Source/JK_MidiClock.cpp

/*
      
 //#######################################################################################
 //Class to insert Midiclock messages into a given MidiBuffer, suitable for block
 //based audio callbacks. The class can act on position jumps e.g. "Loops" by sending a 
 //positioning message.
 //NOTE: No ballistik came in to play so I wouldn't recommend using it to drive a mechanical
 //tape deck!!!
 //
 //solar3d-software, April- 10- 2012
 //#######################################################################################
 
*/
#include "JK_MidiClock.h"

JK_MidiClock::JK_MidiClock() 
                        :wasPlaying(false),
                         syncPpqPosition(-999.0),
                         posChangeThreshold(0.001),
                         ppqToStartSyncAt(0.0),
                         followSongPosition(true),
                         syncFlag(0),
                         ppqOffset(0)
{
	//Prepare Midi messages to avoid blocking the caller of generateMidiclock()!
	continueMessage     = new MidiMessage(MidiMessage::midiContinue());
	stopMessage         = new MidiMessage(MidiMessage::midiStop());
	clockMessage        = new MidiMessage(MidiMessage::midiClock());
	songPositionMessage = new MidiMessage(MidiMessage::songPositionPointer(0));
}
//=================================================================================================
void JK_MidiClock::generateMidiclock(AudioPlayHead::CurrentPositionInfo &lastPosInfo,
                                     MidiBuffer* midiBuffer, const int bufferSize, const double sampleRate)
{
    //###################################Some explanation about musical tempo #################
	//A Time Signature, is two numbers, one on top of the other. The numerator describes the  # 
	//number of Beats in a Bar, while the denominator describes of what note value a Beat is. #
    //So 4/4 would be four quarter-notes per Bar, while 4/2 would be four half-notes per Bar, #
	//4/8 would be four eighth-notes per Bar, and 2/4 would be two quarter-notes per Bar.     #
	//#########################################################################################
    
        
	if (midiBuffer != nullptr)
    {
        //PPQ value of one sample
        const double ppqPerSample = (lastPosInfo.bpm / 60.0) / sampleRate;
        
        //PPQ offset to compensate Midi interface latency
        double hostPpqPosition = lastPosInfo.ppqPosition + ppqOffset * ppqPerSample;;
        
        if (lastPosInfo.isPlaying || lastPosInfo.isRecording)
        {							         
            if (! wasPlaying)
            { 
                //set the point where to start the slave
                ppqToStartSyncAt = getNearestSixteenthInPPQ(hostPpqPosition);
                
                //Special case: Master is set to always start playback from the previous start position... 
                if (positionJumped(syncPpqPosition, hostPpqPosition, sampleRate, ppqPerSample))
                {										
                    //Cue Midiclock slave to the nearest sixteenth note to new start position
                    //because the one calculated in stop mode isn't valid anymore.		
                    sendSongPositionPointerMessage(ppqToStartSyncAt, 0, midiBuffer);
                }
            }
            else
            {
                //Position jump (loop or manually position change while playing)
                if (positionJumped(syncPpqPosition, hostPpqPosition, sampleRate, ppqPerSample))
                {										
                    //set the point where to start the slave
                    ppqToStartSyncAt = getNearestSixteenthInPPQ(hostPpqPosition);
                    
                    //User has changed position manually while playing
                    if (syncFlag == 0)
                    {                   
                        midiBuffer->addEvent(*stopMessage, 0);
                        sendSongPositionPointerMessage(hostPpqPosition, 0, midiBuffer);
                         
                        syncFlag = startSlave_;
                    } 
                    else
                    {                   
                        if (followSongPosition)
                        {
                            sendSongPositionPointerMessage(hostPpqPosition, 0, midiBuffer);
                            
                            syncFlag = startSlave_;
                        }
                        else
                            syncFlag = 0;
                    }
                }
            }
            
            for (int posInBuffer = 0; posInBuffer < bufferSize; ++posInBuffer) 
            {                
                syncPpqPosition = hostPpqPosition + (posInBuffer * ppqPerSample);
                
                const int clockDistanceInSamples = roundToInt((60.0 * sampleRate) / (lastPosInfo.bpm * 24.0));
                const int64 hostSamplePos        = roundToInt64((hostPpqPosition * (60.0 / lastPosInfo.bpm)) * sampleRate);
                const int64 syncSamplePos        = hostSamplePos + posInBuffer;
                
                //Some hosts like Cubase come up with a wacky ppqPosition
                //that could break the timing! Best is to "wait" 
                //here for the right ppqPosition to jump on.
                if (syncPpqPosition >= ppqToStartSyncAt)
                {                             
                    if ((syncFlag & startSlave_) == startSlave_)
                    {
                        midiBuffer->addEvent(*continueMessage, posInBuffer);
                        
                        syncFlag &= cycleEnd_;
                    }
                    
                    //Cycle mode on
                    if (lastPosInfo.isLooping && lastPosInfo.ppqLoopStart != lastPosInfo.ppqLoopEnd)
                    {
                        const double ppqToCycleEnd = fabs(lastPosInfo.ppqLoopEnd - syncPpqPosition);
                        const int64 samplesToCycleEnd = roundToInt64(ppqToCycleEnd * (60.0 / lastPosInfo.bpm) * sampleRate);
                        
                        if ((syncFlag & cycleEnd_) == 0)
                        {
                            if (samplesToCycleEnd <= clockDistanceInSamples) //For fine tuning tweak here
                            {													
                                //We have reached the cycle- end position 
                                //and must stop the Midiclock slave here
                                if (followSongPosition)
                                    midiBuffer->addEvent(*stopMessage, posInBuffer);
                                
                                syncFlag |= cycleEnd_;
                            }
                        }                   
                    }
                }
                
                //For best timing we should never interupt Midiclock messages!
                //Seems that some slaves constantly adjusting their internal clock
                //to Midiclock even if they are in stop mode.
                if (syncSamplePos % clockDistanceInSamples == 0)
                    midiBuffer->addEvent(*clockMessage, posInBuffer);
            }
            
            wasPlaying = true;
        }
        else
        {	        
            //Send positioning message if the user has stopped or if he changed the playhead position  
            //manually in stop mode! This will also initially cue slave after loading plugin instance.
            if (wasPlaying || positionJumped(syncPpqPosition, hostPpqPosition, sampleRate, ppqPerSample))
            {	            
                midiBuffer->addEvent(*stopMessage, 0);				
                sendSongPositionPointerMessage(hostPpqPosition, 0, midiBuffer);
            }
            
            syncPpqPosition = hostPpqPosition;
            
            syncFlag = startSlave_;
            
            wasPlaying = false;
        }
    }
}				
//=================================================================================================
bool JK_MidiClock::positionJumped(const double lastPosInPPQ, const double currentPosInPPQ, 
                                  const double sampleRate, const double ppqPerSample)
{
	//This returns true if the user has changed the playhead position manually or if 
	//a jump has occured! The comperator's default threshold is lastPosInPPQ +- 10ms.
	if (currentPosInPPQ < lastPosInPPQ - ((posChangeThreshold * sampleRate) * ppqPerSample) ||
		currentPosInPPQ > lastPosInPPQ + ((posChangeThreshold * sampleRate) * ppqPerSample))
        return true;
    
	return false;
}
//=================================================================================================
void JK_MidiClock::sendSongPositionPointerMessage(const double ppqPosition, const int posInBuffer, MidiBuffer* buffer)
{
	//This will cue the slave to the NEAREST 
	//16th note to the given ppqPosition.
	int intBeat = int(ceil(ppqPosition * 4));
    
	uint8* pSongPositionTime((uint8*)(songPositionMessage->getRawData()));
	
	*(pSongPositionTime + 1) = (uint8)(intBeat & 0x7f);
	*(pSongPositionTime + 2) = (uint8)((intBeat & 0x3f80)>>7);
    
	buffer->addEvent(*songPositionMessage, posInBuffer);
}