commit 6fa2121c0c1bd96c58ce0a6debea39b04670f43b
parent 0321d13c497fed163e125590be04a78d26271fc8
Author: Hans Petter Selasky <[email protected]>
Date: Wed, 18 May 2016 15:29:54 +0200
Implement audio compressor for ALSA and OSS drivers.
The purpose of the compressor is to avoid DC clipping when the signal
goes beyond the limits of the sample format.
Signed-off-by: Hans Petter Selasky <[email protected]>
Diffstat:
7 files changed, 95 insertions(+), 38 deletions(-)
diff --git a/src/Nio/AlsaEngine.cpp b/src/Nio/AlsaEngine.cpp
@@ -20,6 +20,7 @@ using namespace std;
#include "../Misc/Config.h"
#include "InMgr.h"
#include "AlsaEngine.h"
+#include "Compressor.h"
#include "Nio.h"
AlsaEngine::AlsaEngine(const SYNTH_T &synth)
@@ -28,6 +29,7 @@ AlsaEngine::AlsaEngine(const SYNTH_T &synth)
audio.buffer = new short[synth.buffersize * 2];
name = "ALSA";
audio.handle = NULL;
+ audio.peaks[0] = 0;
midi.handle = NULL;
midi.alsaId = -1;
@@ -251,9 +253,13 @@ short *AlsaEngine::interleave(const Stereo<float *> &smps)
int idx = 0; //possible off by one error here
double scaled;
for(int frame = 0; frame < bufferSize; ++frame) { // with a nod to libsamplerate ...
- scaled = smps.l[frame] * (8.0f * 0x10000000);
+ float l = smps.l[frame];
+ float r = smps.r[frame];
+ stereoCompressor(synth.samplerate, audio.peaks[0], l, r);
+
+ scaled = l * (8.0f * 0x10000000);
shortInterleaved[idx++] = (short int)(lrint(scaled) >> 16);
- scaled = smps.r[frame] * (8.0f * 0x10000000);
+ scaled = r * (8.0f * 0x10000000);
shortInterleaved[idx++] = (short int)(lrint(scaled) >> 16);
}
return shortInterleaved;
diff --git a/src/Nio/AlsaEngine.h b/src/Nio/AlsaEngine.h
@@ -67,6 +67,7 @@ class AlsaEngine:public AudioOut, MidiIn
unsigned int periods;
short *buffer;
pthread_t pThread;
+ float peaks[1];
} audio;
void *processAudio();
diff --git a/src/Nio/Compressor.h b/src/Nio/Compressor.h
@@ -0,0 +1,59 @@
+/*
+ ZynAddSubFX - a software synthesizer
+
+ Compressor.h - simple audio compressor macros
+ Copyright (C) 2016 Hans Petter Selasky
+
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License
+ as published by the Free Software Foundation; either version 2
+ of the License, or (at your option) any later version.
+*/
+
+#ifndef _COMPRESSOR_H_
+#define _COMPRESSOR_H_
+
+#define floatIsValid(x) ({ \
+ float __r = (x) * 0.0; \
+ __r == 0.0 || __r == -0.0; \
+})
+
+#define stereoCompressor(div,pv,l,r) do { \
+ /* \
+ * Don't max the output range to avoid \
+ * overflowing sample rate conversion and \
+ * equalizer filters in the DSP's output \
+ * path. Keep one 10th, 1dB, reserved. \
+ */ \
+ const float __limit = 1.0 - (1.0 / 10.0); \
+ float __peak; \
+ \
+ /* sanity checks */ \
+ __peak = (pv); \
+ if (!floatIsValid(__peak)) \
+ __peak = 0.0; \
+ if (!floatIsValid(l)) \
+ (l) = 0.0; \
+ if (!floatIsValid(r)) \
+ (r) = 0.0; \
+ /* compute maximum */ \
+ if ((l) < -__peak) \
+ __peak = -(l); \
+ else if ((l) > __peak) \
+ __peak = (l); \
+ if ((r) < -__peak) \
+ __peak = -(r); \
+ else if ((r) > __peak) \
+ __peak = (r); \
+ /* compressor */ \
+ if (__peak > __limit) { \
+ (l) /= __peak; \
+ (r) /= __peak; \
+ (l) *= __limit; \
+ (r) *= __limit; \
+ __peak -= __peak / (div); \
+ } \
+ (pv) = __peak; \
+} while (0)
+
+#endif /* _COMPRESSOR_H_ */
diff --git a/src/Nio/OssEngine.cpp b/src/Nio/OssEngine.cpp
@@ -12,6 +12,8 @@
*/
#include "OssEngine.h"
+#include "Compressor.h"
+
#include "../Misc/Util.h"
#include "../Misc/Config.h"
#include "../globals.h"
@@ -186,6 +188,8 @@ OssEngine::OssEngine(const SYNTH_T &synth,
audio.smps.ps32 = new int[synth.buffersize * 2];
memset(audio.smps.ps32, 0, sizeof(int) * synth.buffersize * 2);
memset(&midi.state, 0, sizeof(midi.state));
+
+ audio.peaks[0] = 0;
}
OssEngine::~OssEngine()
@@ -401,21 +405,10 @@ void *OssEngine::audioThreadCb()
while(getAudioEn()) {
const Stereo<float *> smps = getNext();
- float l, r;
for(int i = 0; i < synth.buffersize; ++i) {
- l = smps.l[i];
- r = smps.r[i];
-
- if(l < -1.0f)
- l = -1.0f;
- else
- if(l > 1.0f)
- l = 1.0f;
- if(r < -1.0f)
- r = -1.0f;
- else
- if(r > 1.0f)
- r = 1.0f;
+ float l = smps.l[i];
+ float r = smps.r[i];
+ stereoCompressor(synth.samplerate, audio.peaks[0], l, r);
if (audio.is32bit) {
audio.smps.ps32[i * 2] = (int) (l * 2147483647.0f);
diff --git a/src/Nio/OssEngine.h b/src/Nio/OssEngine.h
@@ -71,6 +71,10 @@ class OssEngine:public AudioOut, MidiIn
short int *ps16;
int *ps32;
} smps;
+
+ /* peak values used for compressor */
+ float peaks[1];
+
bool en;
bool is32bit;
} audio;
diff --git a/src/Nio/OssMultiEngine.cpp b/src/Nio/OssMultiEngine.cpp
@@ -29,6 +29,7 @@
#include "../Misc/Util.h"
#include "OssMultiEngine.h"
+#include "Compressor.h"
extern MiddleWare *middleware;
@@ -53,12 +54,18 @@ OssMultiEngine :: OssMultiEngine(const SYNTH_T &synth,
/* allocate buffer */
smps.ps32 = new int[maxbuffersize / sizeof(int)];
memset(smps.ps32, 0, maxbuffersize);
+
+ /* setup compressor */
+ unsigned peaksize = NUM_MIDI_PARTS * sizeof(float);
+ peaks = new float[peaksize / sizeof(float)];
+ memset(peaks, 0, peaksize);
}
OssMultiEngine :: ~OssMultiEngine()
{
Stop();
delete [] smps.ps32;
+ delete [] peaks;
}
bool
@@ -213,8 +220,6 @@ OssMultiEngine :: audioThreadCb()
while(getAudioEn()) {
int error;
- float l;
- float r;
int x;
int y;
@@ -227,32 +232,18 @@ OssMultiEngine :: audioThreadCb()
if (is32bit) {
for (y = 0; y != synth.buffersize; y++) {
- l = part->partoutl[y];
- if (l < -1.0f)
- l = -1.0f;
- else if (l > 1.0f)
- l = 1.0f;
+ float l = part->partoutl[y];
+ float r = part->partoutr[y];
+ stereoCompressor(synth.samplerate, peaks[x/2], l, r);
smps.ps32[y * channels + x] = (int)(l * 2147483647.0f);
- r = part->partoutr[y];
- if (r < -1.0f)
- r = -1.0f;
- else if (r > 1.0f)
- r = 1.0f;
smps.ps32[y * channels + x + 1] = (int)(r * 2147483647.0f);
}
} else {
for (y = 0; y != synth.buffersize; y++) {
- l = part->partoutl[y];
- if (l < -1.0f)
- l = -1.0f;
- else if (l > 1.0f)
- l = 1.0f;
+ float l = part->partoutl[y];
+ float r = part->partoutr[y];
+ stereoCompressor(synth.samplerate, peaks[x/2], l, r);
smps.ps16[y * channels + x] = (short int)(l * 32767.0f);
- r = part->partoutr[y];
- if (r < -1.0f)
- r = -1.0f;
- else if (r > 1.0f)
- r = 1.0f;
smps.ps16[y * channels + x + 1] = (short int)(r * 32767.0f);
}
}
diff --git a/src/Nio/OssMultiEngine.h b/src/Nio/OssMultiEngine.h
@@ -52,6 +52,9 @@ class OssMultiEngine : public AudioOut
int *ps32;
} smps;
+ /* peak values used for compressor */
+ float *peaks;
+
bool en;
bool is32bit;
