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Adding volume limiting code.

--- a/Changelog

+++ b/Changelog

@@ -80,6 +80,7 @@

   o Matthias Nutt helped add support for specifying multiple effects

     to SoX on the command line.

   o Curt Zirzow added a trim effect to trim off audio data.

+  o Updated ALSA driver to support new interface. Jimen Ching 

 sox-12.16

 ---------

--- a/sox.1

+++ b/sox.1

@@ -116,7 +116,7 @@

 .br

     \fBvibro\fR \fIspeed\fR [ \fIdepth\fR ]

 .br

-    \fBvol\fR \fIgain\fR [ \fItype\fR ]

+    \fBvol\fR \fIgain\fR [ \fItype\fR [ \fIlimitergain\fR ] ] 

 .SH DESCRIPTION

 .I SoX

 is a command line program that can convert most popular audio files

@@ -1026,10 +1026,13 @@

 by the sine wave,

 ranging 0.0 to 1.0 and defaulting to 0.5.

 .TP 10

-vol \fIgain \fB [ \fItype\fB ]

+vol \fIgain\fR [ \fItype\fB [ \fIlimitergain\fR ] ]

 The vol effect is much like the command line option -v.  It allows you to

 adjust the volume of an input file and allows you to specify the adjustment

-in relation to amplitude, power, or dB.  When type is 

+in relation to amplitude, power, or dB.  If \fItype\fR is not specified then

+it defaults to \fIamplitude\fR.

+.br 

+When type is 

 .I amplitude

 then a linear change of the amplitude is performed based on the gain.  Therefore,

 a value of 1.0 will keep the volume the same, 0.0 to < 1.0 will cause the

@@ -1043,8 +1046,15 @@

 .br

 When type is 

 .I dB

-the amplitude is change logarithmically.

+the amplitude is changed logarithmically.

 0.0 is constant while +6 doubles the amplitude.

+.br

+An optional \fIlimitergain\fR value can be specified and should be a

+value much less

+then 1.0 (ie 0.05 or 0.02) and is used only on peaks to prevent clipping.

+Not specifying this parameter will cause no limiter to be used.  In verbose

+mode, this effect will display the percentage of audio data that needed to be

+limited.

 .SH BUGS

 The syntax is horrific.  Thats the breaks when trying to handle all things from the command line.

 .P

--- a/src/vol.c

+++ b/src/vol.c

@@ -28,12 +28,21 @@

 #define TWENTY	  ((VOL_FLOAT)(20.0e0))

 #define VOL_USAGE \

-    "Usage: vol gain type" \

+    "Usage: vol gain [ type [ limitergain ] ]" \

     " (default type=amplitude: 1.0 is constant, <0.0 change phase;" \

-    " type=power 1.0 is constant; type=dB: 0.0 is constant, +6 doubles ampl.)"

+    " type=power 1.0 is constant; type=dB: 0.0 is constant, +6 doubles ampl.)" \

+    " The peak limiter has a gain much less than 1.0 (ie 0.05 or 0.02) which is only" \

+    " used on peaks to prevent clipping. (default is no limiter)"

 typedef struct {

     VOL_FLOAT gain; /* amplitude gain. */

+    

+    int uselimiter; /* boolean: are we using the limiter? */

+    VOL_FLOAT limiterthreshhold;

+    VOL_FLOAT limitergain; /* limiter gain. */

+    int limited; /* number of limited values to report. */

+    int totalprocessed;

+    

     int clipped;    /* number of clipped values to report. */

 } * vol_t;

@@ -46,8 +55,8 @@

 char **argv;

 {

     vol_t vol = (vol_t) effp->priv; 

-    

     vol->gain = ONE; /* default is no change */

+    vol->uselimiter = 0; /* default is no limiter */

     if (n && (!sscanf(argv[0], VOL_FLOAT_SCAN, &vol->gain)))

     {

@@ -77,7 +86,24 @@

 	    break;

 	}

     }

+    

+    if (n>2)

+    {

+    	if ((fabs(vol->gain) < ONE) || !sscanf(argv[2], VOL_FLOAT_SCAN, &vol->limitergain) || !((vol->limitergain > ZERO) && (vol->limitergain < ONE)))

+    	{

+  		st_fail(VOL_USAGE);

+		return ST_EOF;  		

+    	}

+    	

+    	vol->uselimiter = 1; /* ok, we'll use it */

+    	/* The following equation is derived so that there is no discontinuity in output amplitudes */

+    	/* and a LONG_MAX input always maps to a LONG_MAX output when the limiter is activated. */

+    	/* (NOTE: There **WILL** be a discontinuity in the slope of the output amplitudes when using the limiter.) */

+    	vol->limiterthreshhold = LONG_MAX * (ONE - vol->limitergain) / (fabs(vol->gain) - vol->limitergain);

+    }

+    

+

     return ST_SUCCESS;

 }

@@ -103,6 +129,8 @@

     }

     vol->clipped = 0;

+    vol->limited = 0;

+    vol->totalprocessed = 0;

     return ST_SUCCESS;

 }

@@ -141,6 +169,8 @@

 {

     vol_t vol = (vol_t) effp->priv;

     register VOL_FLOAT gain = vol->gain;

+    register VOL_FLOAT limiterthreshhold = vol->limiterthreshhold;

+    register VOL_FLOAT sample;

     register LONG len;

     len = MIN(*osamp, *isamp);

@@ -148,10 +178,38 @@

     /* report back dealt with amount. */

     *isamp = len; *osamp = len;

-    /* quite basic, with clipping */

-    for (;len>0; len--)

-	*obuf++ = clip(vol, gain * *ibuf++);

+    if (vol->uselimiter)

+    {

+	vol->totalprocessed += len;

+	

+	for (;len>0; len--)

+	    {

+	    	sample = *ibuf++;

+	    	

+	    	if (sample > limiterthreshhold)

+	    	{

+	    		sample =  (LONG_MAX - vol->limitergain * (LONG_MAX - sample));

+	    		vol->limited++;

+	    	}

+	    	else if (sample < -limiterthreshhold)

+	    	{

+	    		sample = -(LONG_MAX - vol->limitergain * (LONG_MAX + sample));

+	    		vol->limited++;

+	    	}

+	    	else

+	    	{

+	    		sample = gain * sample;

+	    	}

+		*obuf++ = clip(vol, sample);

+	    }

+    }

+    else

+    {

+    	/* quite basic, with clipping */

+    	for (;len>0; len--)

+		*obuf++ = clip(vol, gain * *ibuf++);

+    }

     return ST_SUCCESS;

 }

@@ -163,6 +221,11 @@

 eff_t effp;

 {

     vol_t vol = (vol_t) effp->priv;

+    if (vol->limited)

+    {

+	st_warn("VOL limited %d values (%d percent).", 

+	     vol->limited, (int) (vol->limited * 100.0 / vol->totalprocessed));

+    }

     if (vol->clipped) 

     {

 	st_warn("VOL clipped %d values, amplitude gain=%f too high...",