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* experimental channel effects processing
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* provided under GNU General Public License
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* contents : channel pre-mix , effect struct definition
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* Nicolas Witczak juillet 1998
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* witczak@geocities.com
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remarks about occured changes
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+ each note from a voice was directly mixed in the common_buffer
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in order to add channel effect we need to insert an extra and inefficient mixing
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so implementing the scheme :
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voice -> channel_buffer -> common_buffer -> output_buffer
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the only optimisation I see from now is to keep track of empty
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channel_buffer in order to skip them from processing and mixing
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+ I tried to keep the C but yet modular style of prog , hope it'll be usefull
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+ this experimental add on can be switched on and off with the define CHANNEL_EFFECT
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extern int XG_effect_chorus_is_celeste_flag;
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extern int XG_effect_chorus_is_flanger_flag;
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extern int XG_effect_chorus_is_phaser_flag;
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/**************************************************************************/
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/** exported from playmidi.c
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extern MidiEvent *event_list, *current_event;
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extern uint32 sample_count, current_sample;
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extern int32 *buffer_pointer;
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/**************************************************************************/
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/** helpers functions : circular buffer impl */
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/** used in several effect that need phase modulation */
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#define FRACTION ( 1 << FRACTION_BITS )
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/**************************************************************************/
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/** cirbuff structure : manage a circular buffer : given x it retreives x * z-1 , x * z-2 ...
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* accesible values are (ptr->m_pCur)[0] , (ptr->m_pCur)[-1] ... (ptr->m_pCur)[ -m_count + 1 ]
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/** m_count : active content sample count */
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/** m_pCur : represent the past sample content ] pLast , m_pCur ]
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* transient should not be stored
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/** m_pBufCur , m_pBufLast represent the actual buffer ] m_pBufLast , m_pBufCur ] such that
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* m_pBufLast <= m_pLast < m_pCur <= m_pBufCur
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/** create_cirbuff : initialize a circular buffer given as pThis with an active size of count */
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void create_cirbuff( cirbuff* pThis , uint32 count ) ;
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/** delete_cirbuff : delete a circular buffer given as pThis */
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void delete_cirbuff( cirbuff* pThis ) ;
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/** redim_cirbuff : resize a circular buffer given as pThis with an new size of count
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void redim_cirbuff( cirbuff* pThis , uint32 count ) ;
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/** pushval_cirbuff : insert newSample inside pThis */
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void pushval_cirbuff( cirbuff* pThis , int32 newSample ) ;
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/** shift_cirbuff : shift past samples inside pThis of uiShift complete with 0 sample val */
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void shift_cirbuff( cirbuff* pThis , uint32 uiShift ) ;
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/* dump_cirbuff : output a ascii dump of this buffer ( for debugging) */
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void dump_cirbuff( cirbuff* pThis , FILE* pOutFile ) ;
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/**************************************************************************/
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* this structure represent a particuliar kind of effect
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* ie rev , chorus, acting on a single channel buffer
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/** called each time a new mono data chunk is to be processed
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* PARAM : this Effect derived structure
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* PARAM : the channel buffer to process
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* PARAM : number of samples to process
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* PARAM : 1 if this buffer is not null signal, may be set to 1 by this function
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* RELATED GLOBAL VAR : sample_count, current_sample (current sample counter)
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void (*m_pfnActionMono)( void* , int32* , uint32 , int* ) ;
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/** called each time a new stereo data chunk is to be processed
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* PARAM : this Effect derived structure
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* PARAM : the channel buffer to process
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* PARAM : number of samples to process
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* PARAM : 1 if this buffer is not null signal, may be set to 1 by this function
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* RELATED GLOBAL VAR : sample_count, current_sample (current sample counter)
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* RQ : sample buffer contains 2 * PARAM2 samples
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void (*m_pfnActionStereo)( void* , int32* , uint32 , int* ) ;
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/** hook function : called when a controller have changed
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* PARAM : this Effect derived structure
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void (*m_pfnCtrlChange)( void* , MidiEvent* pCurrentEvent );
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/** hook function : called when a controller must be reseted in a inactive state
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* PARAM : this Effect derived structure
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void (*m_pfnCtrlReset)( void* );
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/** accessor : give the name of this effect
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* fill the buffer given as argument ( max size 16 char including \0 )
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void (*m_pfnName)( char* );
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/** destructor function
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* PARAM : this Effect derived structure
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void (*m_pfnDestruct)( void* );
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/**************************************************************************/
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/** Effect construction function prototype
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* this function is called once for each effect on each channel upon
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* PARAM : channel attached to the newly constructed Effect obj
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* may be used to access the channel array
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* RELATED GLOBAL VAR : channel array
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* RETURN : shall return an allocated effect object whose structure is compatible
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* whith the Effect one
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typedef Effect* (*EFFECT_CTOR)(void) ;
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/**************************************************************************/
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/** null terminated list effects types contructors
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extern EFFECT_CTOR effect_type_list[] ;
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/* effect_list[effect type][channel] , list of
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* active effects for each channel in the same order than former list
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* RQ1 : may contains 0 if not activated
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* RQ2 : placed in the same than for the effect_type_list array
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extern Effect* effect_list[][MAXCHAN] ;
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extern char effect_name[][MAXCHAN] ;
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/**************************************************************************/
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/** effect_ctrl_change
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* this function is called in order to give a chance to ctrl effect
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* object to update their parameters
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* PARAM pCurrentEvent : midi event reflecting changes
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void effect_ctrl_change( MidiEvent* pCurrentEvent );
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/**************************************************************************/
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/** effect_ctrl_reset
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* this function is called in order to reset all ctrl effect attached to a channel
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* object to update their parameters
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* PARAM idChannel : midi channel number
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void effect_ctrl_reset( int idChannel );
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/**************************************************************************/
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* this function turns on or off effect processing according to iSwitch
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void effect_activate( int iSwitch ) ;
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/****************************************************************************************/
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extern int opt_effect;
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extern Effect* ChorusCtor(void) ;
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extern Effect* PhaserCtor(void) ;
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extern Effect* CelesteCtor(void) ;
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extern Effect* ReverbCtor(void) ;
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extern int init_effect(void) ;
added
removed
kmidi/effects.h
