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/* compress.c
* Compressor logic
*
* (c)2007 busybee (http://beesbuzz.biz/
* Licensed under the terms of the LGPL. See the file COPYING for details.
*/
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "config.h"
#include "compress.h"
struct Compressor {
//! The compressor's preferences
struct CompressorConfig prefs;
//! History of the peak values
int *peaks;
//! History of the gain values
int *gain;
//! History of clip amounts
int *clipped;
unsigned int pos;
unsigned int bufsz;
};
struct Compressor *Compressor_new(unsigned int history)
{
struct Compressor *obj = malloc(sizeof(struct Compressor));
obj->prefs.target = TARGET;
obj->prefs.maxgain = GAINMAX;
obj->prefs.smooth = GAINSMOOTH;
obj->peaks = obj->gain = obj->clipped = NULL;
obj->bufsz = 0;
obj->pos = 0;
Compressor_setHistory(obj, history);
return obj;
}
void Compressor_delete(struct Compressor *obj)
{
if (obj->peaks)
free(obj->peaks);
if (obj->gain)
free(obj->gain);
if (obj->clipped)
free(obj->clipped);
free(obj);
}
static int *resizeArray(int *data, int newsz, int oldsz)
{
data = realloc(data, newsz*sizeof(int));
if (newsz > oldsz)
memset(data + oldsz, 0, sizeof(int)*(newsz - oldsz));
return data;
}
void Compressor_setHistory(struct Compressor *obj, unsigned int history)
{
if (!history)
history = BUCKETS;
obj->peaks = resizeArray(obj->peaks, history, obj->bufsz);
obj->gain = resizeArray(obj->gain, history, obj->bufsz);
obj->clipped = resizeArray(obj->clipped, history, obj->bufsz);
obj->bufsz = history;
}
struct CompressorConfig *Compressor_getConfig(struct Compressor *obj)
{
return &obj->prefs;
}
void Compressor_Process_int16(struct Compressor *obj, int16_t *audio,
unsigned int count)
{
struct CompressorConfig *prefs = Compressor_getConfig(obj);
int16_t *ap;
unsigned int i;
int *peaks = obj->peaks;
int curGain = obj->gain[obj->pos];
int newGain;
int peakVal = 1;
int peakPos = 0;
int slot = (obj->pos + 1) % obj->bufsz;
int *clipped = obj->clipped + slot;
unsigned int ramp = count;
int delta;
ap = audio;
for (i = 0; i < count; i++)
{
int val = *ap++;
if (val < 0)
val = -val;
if (val > peakVal)
{
peakVal = val;
peakPos = i;
}
}
peaks[slot] = peakVal;
for (i = 0; i < obj->bufsz; i++)
{
if (peaks[i] > peakVal)
{
peakVal = peaks[i];
peakPos = 0;
}
}
//! Determine target gain
newGain = (1 << 10)*prefs->target/peakVal;
//! Adjust the gain with inertia from the previous gain value
newGain = (curGain*((1 << prefs->smooth) - 1) + newGain)
>> prefs->smooth;
//! Make sure it's no more than the maximum gain value
if (newGain > (prefs->maxgain << 10))
newGain = prefs->maxgain << 10;
//! Make sure it's no less than 1:1
if (newGain < (1 << 10))
newGain = 1 << 10;
//! Make sure the adjusted gain won't cause clipping
if ((peakVal*newGain >> 10) > 32767)
{
newGain = (32767 << 10)/peakVal;
//! Truncate the ramp time
ramp = peakPos;
}
//! Record the new gain
obj->gain[slot] = newGain;
if (!ramp)
ramp = 1;
if (!curGain)
curGain = 1 << 10;
delta = (newGain - curGain) / (int)ramp;
ap = audio;
*clipped = 0;
for (i = 0; i < count; i++)
{
int sample;
//! Amplify the sample
sample = *ap*curGain >> 10;
if (sample < -32768)
{
*clipped += -32768 - sample;
sample = -32768;
} else if (sample > 32767)
{
*clipped += sample - 32767;
sample = 32767;
}
*ap++ = sample;
//! Adjust the gain
if (i < ramp)
curGain += delta;
else
curGain = newGain;
}
obj->pos = slot;
}
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