Revision of handling of frameoffset for NPH, SPH

Change in handling of frameoffset for multistreamed instruments and sampletracks.
- Instead of holding the offset for the lifetime of the playhandle, negate the offset in the first period
- Multistream-instruments require some small changes: they have to now check for the offset and accordingly leave empty space in the start of the period (already done in this commit)
- There are possibly optimizations that can be done later
- This change is necessary so that we can have sample-exact models, and sample-exact vol/pan knobs for all instruments. Earlier multistream instruments were always rendering some frames ahead-of-time, so applying sample-exact data for them would have been impossible, since we don't have the future-values yet...

include/Mixer.h

@@ -312,7 +312,6 @@ public:
 	// audio-buffer-mgm
 	void bufferToPort( const sampleFrame * _buf,
 					const fpp_t _frames,
-					const f_cnt_t _offset,
 					stereoVolumeVector _volume_vector,
 					AudioPort * _port );
 

include/NotePlayHandle.h

@@ -74,6 +74,16 @@ public:
 	{
 		return m_midiChannel;
 	}
+	
+	/*! convenience function that returns offset for the first period and zero otherwise,
+		used by instruments to handle the offset: instruments have to check this property and 
+		add the correct number of empty frames in the beginning of the period */
+	f_cnt_t noteOffset() const
+	{
+		return m_totalFramesPlayed == 0
+			? offset()
+			: 0;
+	}
 
 	const float& frequency() const
 	{
@@ -94,7 +104,7 @@ public:
 	/*! Returns whether playback of note is finished and thus handle can be deleted */
 	virtual bool isFinished() const
 	{
-		return m_released && framesLeft() <= 0 && m_scheduledNoteOff < 0;
+		return m_released && framesLeft() <= 0;
 	}
 
 	/*! Returns number of frames left for playback */
@@ -264,7 +274,6 @@ private:
 											// played after release
 	f_cnt_t m_releaseFramesDone;			// number of frames done after
 											// release of note
-	f_cnt_t m_scheduledNoteOff;			// variable for scheduling noteoff at next period
 	NotePlayHandleList m_subNotes;			// used for chords and arpeggios
 	volatile bool m_released;				// indicates whether note is released
 	bool m_hasParent;

include/PlayHandle.h

@@ -88,8 +88,8 @@ public:
 	virtual void play( sampleFrame* buffer ) = 0;
 	virtual bool isFinished( void ) const = 0;
 
-	// returns how many frames this play-handle is aligned ahead, i.e.
-	// at which position it is inserted in the according buffer
+	// returns the frameoffset at the start of the playhandle,
+	// ie. how many empty frames should be inserted at the start of the first period
 	f_cnt_t offset() const
 	{
 		return m_offset;

include/SamplePlayHandle.h

@@ -22,8 +22,8 @@
  *
  */
 
-#ifndef _SAMPLE_PLAY_HANDLE_H
-#define _SAMPLE_PLAY_HANDLE_H
+#ifndef SAMPLE_PLAY_HANDLE_H
+#define SAMPLE_PLAY_HANDLE_H
 
 #include "Mixer.h"
 #include "SampleBuffer.h"
@@ -49,7 +49,7 @@ public:
 	}
 
 
-	virtual void play( sampleFrame * _working_buffer );
+	virtual void play( sampleFrame * buffer );
 	virtual bool isFinished() const;
 
 	virtual bool isFromTrack( const track * _track ) const;