Adaptive Silence Detection
[Audio Manipulation Algorithms]

---

Detailed Description

Typedefs
typedef typedefPJ_BEGIN_DECL struct pjmedia_silence_det	pjmedia_silence_det
Functions
pj_status_t	pjmedia_silence_det_create (pj_pool_t *pool, unsigned clock_rate, unsigned samples_per_frame, pjmedia_silence_det **p_sd)
pj_status_t	pjmedia_silence_det_set_name (pjmedia_silence_det *sd, const char *name)
pj_status_t	pjmedia_silence_det_set_fixed (pjmedia_silence_det *sd, int threshold)
pj_status_t	pjmedia_silence_det_set_adaptive (pjmedia_silence_det *sd, int threshold)
pj_status_t	pjmedia_silence_det_set_params (pjmedia_silence_det *sd, int before_silence, int recalc_time1, int recalc_time2)
pj_status_t	pjmedia_silence_det_disable (pjmedia_silence_det *sd)
pj_bool_t	pjmedia_silence_det_detect (pjmedia_silence_det *sd, const pj_int16_t samples[], pj_size_t count, pj_int32_t *p_level)
pj_int32_t	pjmedia_calc_avg_signal (const pj_int16_t samples[], pj_size_t count)
pj_bool_t	pjmedia_silence_det_apply (pjmedia_silence_det *sd, pj_uint32_t level)

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Typedef Documentation

typedef typedefPJ_BEGIN_DECL struct pjmedia_silence_det pjmedia_silence_det

Opaque declaration for silence detector.

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Function Documentation

pj_status_t pjmedia_silence_det_create	(	pj_pool_t *	pool,
		unsigned	clock_rate,
		unsigned	samples_per_frame,
		pjmedia_silence_det **	p_sd
	)

Create voice activity detector with default settings. The default settings are set to adaptive silence detection with the default threshold.

Parameters:

	pool	Pool for allocating the structure.
	clock_rate	Clock rate.
	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.
	p_sd	Pointer to receive the silence detector instance.

Returns:

PJ_SUCCESS on success.

pj_status_t pjmedia_silence_det_set_name	(	pjmedia_silence_det *	sd,
		const char *	name
	)

Set silence detector name to identify the particular silence detector instance in the log.

Parameters:

	sd	The silence detector.
	name	Name.

Returns:

PJ_SUCCESS on success.

pj_status_t pjmedia_silence_det_set_fixed	(	pjmedia_silence_det *	sd,
		int	threshold
	)

Set the sd to operate in fixed threshold mode. With fixed threshold mode, the threshold will not be changed adaptively.

Parameters:

	sd	The silence detector
	threshold	The silence threshold, or -1 to use default threshold.

Returns:

PJ_SUCCESS on success.

pj_status_t pjmedia_silence_det_set_adaptive	(	pjmedia_silence_det *	sd,
		int	threshold
	)

Set the sd to operate in adaptive mode. This is the default mode when the silence detector is created.

Parameters:

	sd	The silence detector
	threshold	Initial threshold to be set, or -1 to use default threshold.

Returns:

PJ_SUCCESS on success.

pj_status_t pjmedia_silence_det_set_params	(	pjmedia_silence_det *	sd,
		int	before_silence,
		int	recalc_time1,
		int	recalc_time2
	)

Set other silence detector parameters.

Parameters:

	sd	The silence detector
	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.
	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).
	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).

Returns:

PJ_SUCCESS on success.

pj_status_t pjmedia_silence_det_disable

(

pjmedia_silence_det *

sd

)

Disable the silence detector.

Parameters:

sd

The silence detector

Returns:

PJ_SUCCESS on success.

pj_bool_t pjmedia_silence_det_detect	(	pjmedia_silence_det *	sd,
		const pj_int16_t	samples[],
		pj_size_t	count,
		pj_int32_t *	p_level
	)

Perform voice activity detection on the given input samples. This function uses pjmedia_calc_avg_signal() and pjmedia_silence_det_apply() for its calculation.

Parameters:

	sd	The silence detector instance.
	samples	Pointer to 16-bit PCM input samples.
	count	Number of samples in the input.
	p_level	Optional pointer to receive average signal level of the input samples.

Returns:

Non zero if signal is silence.

pj_int32_t pjmedia_calc_avg_signal	(	const pj_int16_t	samples[],
		pj_size_t	count
	)

Calculate average signal level for the given samples.

Parameters:

	samples	Pointer to 16-bit PCM samples.
	count	Number of samples in the input.

Returns:

The average signal level, which simply is total level divided by number of samples.

pj_bool_t pjmedia_silence_det_apply	(	pjmedia_silence_det *	sd,
		pj_uint32_t	level
	)

Perform voice activity detection, given the specified average signal level.

Parameters:

	sd	The silence detector instance.
	level	Signal level.

Returns:

Non zero if signal is silence.