myvtm/Other/unix/libaudioframework/other/silencedet.h

#ifndef __SILENCEDET_H__
#define __SILENCEDET_H__

#pragma once

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Adaptive Silence Detector
 */

typedef struct silence_det_t silence_det_t;


/**
 * Create voice activity detector with default settings. The default settings
 * are set to adaptive silence detection with the default threshold.
 *
 * @param pool		    Pool for allocating the structure.
 * @param clock_rate	    Clock rate.
 * @param samples_per_frame Number of samples per frame. The clock_rate and
 *			    samples_per_frame is only used to calculate the
 *			    frame time, from which some timing parameters
 *			    are calculated from.
 * @param p_sd		    Pointer to receive the silence detector instance.
 *
 * @return		    0 on success.
 */
int silence_det_create(unsigned clock_rate,unsigned samples_per_frame,silence_det_t **p_sd );

void silence_det_destory(silence_det_t *sd);

/**
 * Set the sd to operate in fixed threshold mode. With fixed threshold mode,
 * the threshold will not be changed adaptively.
 *
 * @param sd		    The silence detector
 * @param threshold	    The silence threshold, or -1 to use default
 *			    threshold.
 *
 * @return		    0 on success.
 */
int silence_det_set_fixed( silence_det_t *sd,int threshold );

/**
 * Set the sd to operate in adaptive mode. This is the default mode
 * when the silence detector is created.
 *
 * @param sd		    The silence detector
 * @param threshold	    Initial threshold to be set, or -1 to use default
 *			    threshold.
 *
 * @return		    0 on success.
 */
int silence_det_set_adaptive(silence_det_t *sd,int threshold);

/**
 * Set other silence detector parameters.
 *
 * @param sd		    The silence detector
 * @param before_silence    Minimum duration of silence (in msec) before 
 *			    silence is reported. If -1 is specified, then
 *			    the default value will be used. The default is
 *			    400 msec.
 * @param recalc_time1	    The interval (in msec) to recalculate threshold
 *			    in non-silence condition when adaptive silence 
 *			    detection is set. If -1 is specified, then the 
 *			    default value will be used. The default is 4000
 *			    (msec).
 * @param recalc_time2	    The interval (in msec) to recalculate threshold
 *			    in silence condition when adaptive silence detection
 *			    is set. If -1 is specified, then the default value 
 *			    will be used. The default value is 2000 (msec).
 *
 * @return		    0 on success.
 */
int silence_det_set_params( silence_det_t *sd,int before_silence,int recalc_time1,int recalc_time2);


/**
 * Disable the silence detector.
 *
 * @param sd		The silence detector
 *
 * @return		0 on success.
 */
int silence_det_disable( silence_det_t *sd );


/**
 * Perform voice activity detection on the given input samples. This
 * function uses #calc_avg_signal() and #silence_det_apply()
 * for its calculation.
 *
 * @param sd		The silence detector instance.
 * @param samples	Pointer to 16-bit PCM input samples.
 * @param count		Number of samples in the input.
 * @param p_level	Optional pointer to receive average signal level
 *			of the input samples.
 *
 * @return		Non zero if signal is silence.
 */
int silence_det_detect( silence_det_t *sd,
					       const short samples[],
					       size_t count,
					       int *p_level);


/**
 * Calculate average signal level for the given samples.
 *
 * @param samples	Pointer to 16-bit PCM samples.
 * @param count		Number of samples in the input.
 *
 * @return		The average signal level, which simply is total level
 *			divided by number of samples.
 */
int calc_avg_signal( const short samples[],size_t count );



/**
 * Perform voice activity detection, given the specified average signal
 * level.
 *
 * @param sd		The silence detector instance.
 * @param level		Signal level.
 *
 * @return		Non zero if signal is silence.
 */
int silence_det_apply( silence_det_t *sd,unsigned int level);


#ifdef __cplusplus
} // extern "C" {
#endif

#endif //__SILENCEDET_H__