AutoGain.h File Reference

Automatic Gain Control (AGC) More...

#include "EQ.h"

Go to the source code of this file.

Classes
struct	AutoGainParam
	AutoGain parameters. More...
struct	AutoGain
	AutoGain runtime structure. More...
Defines
#define	kAutoGainClipDb   -3.0
#define	kAutoGainOKDb   -21.0
#define	kAutoGainLowDb   -36.0
#define	kAutoGainIncrTime   1.0
#define	kAutoGainDecrTime   0.200
#define	kAutoGainIncr   0.05
#define	kAutoGainIncrThresh   0.20
Typedefs
typedef void	AutoGainSetGainFn (void *arg, int isIncr, float incr)
	Callback to adjust gain.
Enumerations
enum	AutoGainLevel {   IGNORE_LEVEL, LOW_LEVEL, OK_LEVEL, CLIP_LEVEL,   NUM_LEVEL }
Functions
AutoGain *	AutoGainNew (AutoGainParam *param, AutoGainSetGainFn *fn, void *arg)
	Create AutoGain object.
void	AutoGainDelete (AutoGain *p)
	Destructor.
void	AutoGainProcessShort (AutoGain *p, short *input)
	Process short samples.
void	AutoGainProcessFloat (AutoGain *p, float *input)
	Process float samples (-1.0 to +1.0)
void	AutoGainProcessPeakVal (AutoGain *p, float peakVal)
	Process peak value.
void	AutoGainSetThresh (AutoGain *p, float clipDb, float okDb, float lowDb)
	Set thresholds.
void	AutoGainSetUpdateTimes (AutoGain *p, float incrTimeSec, float decrTimeSec)
	Set update times.
void	AutoGainReset (AutoGain *p)
	Reset to initial condition.
void	AutoGainGetDefaultParam (AutoGainParam *param)
	Get default parameters.

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Detailed Description

Automatic Gain Control (AGC)

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Define Documentation

#define kAutoGainClipDb   -3.0

decrease gain above this

#define kAutoGainDecrTime   0.200

min time between gain decreases

#define kAutoGainIncr   0.05

20 gain steps

#define kAutoGainIncrThresh   0.20

20% of buffers low without ok will increase

#define kAutoGainIncrTime   1.0

min time between gain increases

#define kAutoGainLowDb   -36.0

levels below this are ignored

#define kAutoGainOKDb   -21.0

increase gain between low and ok

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Typedef Documentation

typedef void AutoGainSetGainFn(void *arg, int isIncr, float incr)

Callback to adjust gain.

Parameters:

	arg	user specified argument
[in]	isIncr	true if increment, false if decrement gain
[in]	incr	increment, typically 0.01 to 0.10

The function should never decrease gain to 0 because this can mute! AutoGain never learns the actual volume level, it simply requests that it be raised or lowered by the incr amount specified in the parameters.

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Enumeration Type Documentation

enum AutoGainLevel

Enumerator:

IGNORE_LEVEL	level below low
LOW_LEVEL	level beween low and ok
OK_LEVEL	level between ok and clip
CLIP_LEVEL	level is above clip
NUM_LEVEL	number of histogram bins

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Function Documentation

void AutoGainGetDefaultParam

(

AutoGainParam *

param

)

Get default parameters.

Parameters:

[out]

param

pointer to parameter object to initialize

Caller must set up numChan, sampRate and framesPerBuf.

AutoGain* AutoGainNew	(	AutoGainParam *	param,
		AutoGainSetGainFn *	fn,
		void *	arg
	)

Create AutoGain object.

Parameters:

[in]	param	parameters
[in]	fn	callback function
[in]	arg	argument to callback function

Returns AutoGain object.

void AutoGainProcessFloat	(	AutoGain *	p,
		float *	input
	)

Process float samples (-1.0 to +1.0)

Parameters:

p	AutoGain object
input	pointer to samples

void AutoGainProcessPeakVal	(	AutoGain *	p,
		float	peakVal
	)

Process peak value.

Parameters:

p	AutoGain object
peakVal	peak value, 1.0 is 0 dBFS

Internal function to process peak value of buffer.

void AutoGainProcessShort	(	AutoGain *	p,
		short *	input
	)

Process short samples.

Parameters:

p	AutoGain object
input	pointer to samples