/* 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 <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; }