Increasing microphone gain programmatically - c++

Question

I'm trying to increase the gain of my microphone for VOIP scenarios.
I'm using PortAudio to acquire an input stream (with samples of type paFloat32), I'm multiplying these values by a float, then passing the resultant stream to an output device.
Note: I'm passing it to a virtual output device that automatically redirects to a virtual input device (program: VB-Cable), which VOIP applications can use as the microphone input with gain applied.
I'm wondering if there are better ways to increase gain of a signal that maintain quality better.
I've read that it's better to perform such gain calculations by first converting the input to a higher precision format, performing the gain multiplication in this format, apply clipping, then cast back down to the original.
I'm not sure how to do this with PortAudio's paFloat32 type, I've included my attempt commented out in the source code. When I enable it there is notable noise issues even with gain set to 1.
Dependencies: tinycon, PortAudio
Compiling: g++ main.cpp tinycon.cpp -o main -L./ -lcygportaudio-2 -lrt -lm -pthread -std=c++11
Code:
#include "portaudio.h"
#include <iostream>
#include <chrono>
#include <thread>
#include <mutex>
#include "tinycon.h"
#define SAMPLE_RATE (44100)
#define FRAMES_PER_BUFFER (441)
#define DITHER_FLAG (1)
#define PA_SAMPLE_TYPE paFloat32
#define SAMPLE_SIZE (4)
#define SAMPLE_SILENCE (0)
#define PRINTF_S_FORMAT "%f"
/*******************************************************************/
double multiplier = 1.0;
double multiplierStep = 0.1;
int main(int argc, char **argv);
int xrun(PaStream *stream, int err, char* sampleBlock);
void error1(PaStream *stream, char* sampleBlock);
void error2(PaStream *stream, int err);
void listDevices();
// Use tinycon and a second thread for non blocking input
class tcon : public tinyConsole
{
public:
tcon (std::string s): tinyConsole(s) {;}
int hotkeys(char c)
{
if (c == 's') {
if (multiplier >= (0+multiplierStep)) {
multiplier -= multiplierStep;
}
printf( "Multiplier: %f\n", multiplier );
return 1;
}
if (c == 'w') {
multiplier += multiplierStep;
printf( "Multiplier: %f\n", multiplier );
return 1;
}
return 0;
}
};
int inputThread() {
tcon tc (std::string(""));
tc.run();
}
void listDevices() {
int i, numDevices, defaultDisplayed;
const PaDeviceInfo *deviceInfo;
Pa_Initialize();
numDevices = Pa_GetDeviceCount();
printf( "Number of devices = %d\n", numDevices );
int isInputDevice = 0;
for( i=0; i<numDevices; i++ )
{
deviceInfo = Pa_GetDeviceInfo( i );
int isInputDevice = (deviceInfo->maxInputChannels > 0);
printf( "%sDeviceID: %d, Name: %s\n", (isInputDevice ? "Input" : "Output"), i, deviceInfo->name);
}
fprintf (stderr, "Press any key to close\n");
getch();
}
int main (int argc, char **argv)
{
int c;
int inputDeviceId = -1;
int outputDeviceId = -1;
opterr = 0;
const char* helpMessage =
"-h : show this help message\n"
"-i <int> : select the INPUT DEVICE by id\n"
"-o <int> : select the OUPUT DEVICE by id\n"
"-m <double> : SIGNAL MULTIPLIER\n"
"-s <double> : SIGNAL MULTIPLIER STEP (press w or s while console focused to go up and down by this ammount.\n"
"-d : list devices\n";
while ((c = getopt (argc, argv, "i:o:l:m:s:hd")) != -1) {
switch (c) {
case 'i':
inputDeviceId = atoi(optarg);
break;
case 'o':
outputDeviceId = atoi(optarg);
break;
case 'm':
multiplier = atof(optarg);
break;
case 's':
multiplierStep = atof(optarg);
break;
case 'd':
listDevices();
return 0;
case '?':
if (isprint (optopt))
fprintf (stderr, "Unknown option `-%c'.\n", optopt);
else
fprintf (stderr, "Unknown option character `\\x%x'.\n", optopt);
case 'h':
fprintf (stderr, helpMessage);
fprintf (stderr, "Press any key to close\n");
getch();
return 1;
default:
abort ();
}
}
// Start non blocking input thread
std::thread nonBlockingInputThread(inputThread);
PaStreamParameters inputParameters, outputParameters;
PaStream *stream = NULL;
PaError err;
const PaDeviceInfo* inputInfo;
const PaDeviceInfo* outputInfo;
char *sampleBlock = NULL;
int i;
int numBytes;
int numChannels;
err = Pa_Initialize();
if( err != paNoError ) error2(stream, err);
inputParameters.device = (inputDeviceId == -1) ? Pa_GetDefaultInputDevice() : inputDeviceId; /* default input device */
inputInfo = Pa_GetDeviceInfo( inputParameters.device );
outputParameters.device = (outputDeviceId == -1) ? Pa_GetDefaultOutputDevice() : outputDeviceId; /* default output device */
outputInfo = Pa_GetDeviceInfo( outputParameters.device );
numChannels = inputInfo->maxInputChannels < outputInfo->maxOutputChannels
? inputInfo->maxInputChannels : outputInfo->maxOutputChannels;
inputParameters.channelCount = numChannels;
inputParameters.sampleFormat = PA_SAMPLE_TYPE;
inputParameters.suggestedLatency = inputInfo->defaultHighInputLatency ;
inputParameters.hostApiSpecificStreamInfo = NULL;
printf( "Input device # %d.\n", inputParameters.device );
printf( " Name: %s\n", inputInfo->name );
outputParameters.channelCount = numChannels;
outputParameters.sampleFormat = PA_SAMPLE_TYPE;
outputParameters.suggestedLatency = outputInfo->defaultHighOutputLatency;
outputParameters.hostApiSpecificStreamInfo = NULL;
printf( "Output device # %d.\n", outputParameters.device );
printf( " Name: %s\n", outputInfo->name );
/* -- setup -- */
err = Pa_OpenStream(
&stream,
&inputParameters,
&outputParameters,
SAMPLE_RATE,
FRAMES_PER_BUFFER,
paClipOff, /* we won't output out of range samples so don't bother clipping them */
NULL, /* no callback, use blocking API */
NULL ); /* no callback, so no callback userData */
if( err != paNoError ) error2(stream, err);
numBytes = FRAMES_PER_BUFFER * numChannels * SAMPLE_SIZE ;
sampleBlock = (char *) malloc( numBytes );
if( sampleBlock == NULL )
{
printf("Could not allocate record array.\n");
error1(stream, sampleBlock);
}
err = Pa_StartStream( stream );
if( err != paNoError ) error1(stream, sampleBlock);
while (1) {
// You may get underruns or overruns if the output is not primed by PortAudio.
err = Pa_ReadStream( stream, sampleBlock, FRAMES_PER_BUFFER );
if( err ) xrun(stream, err, sampleBlock);
int blockIndex;
float* sampleBlockShort = (float*)sampleBlock;
for (blockIndex = 0; blockIndex < FRAMES_PER_BUFFER; blockIndex++) {
/*
double dSample = (double)sampleBlockShort[blockIndex];
dSample *= multiplier;
if (dSample > 32767.0) dSample = 32767.0;
if (dSample < -32768.0) dSample = -32768.0;
sampleBlockShort[blockIndex] = (short)dSample;
*/
sampleBlockShort[blockIndex] *= multiplier;
}
err = Pa_WriteStream( stream, sampleBlock, FRAMES_PER_BUFFER );
if( err ) xrun(stream, err, sampleBlock);
}
printf("Wire off.\n"); fflush(stdout);
err = Pa_StopStream( stream );
if( err != paNoError ) error1(stream, sampleBlock);
free( sampleBlock );
Pa_Terminate();
return 0;
}
int xrun(PaStream *stream, int err, char* sampleBlock) {
printf("err = %d\n", err); fflush(stdout);
if( stream ) {
Pa_AbortStream( stream );
Pa_CloseStream( stream );
}
free( sampleBlock );
Pa_Terminate();
if( err & paInputOverflow )
fprintf( stderr, "Input Overflow.\n" );
if( err & paOutputUnderflow )
fprintf( stderr, "Output Underflow.\n" );
return -2;
}
void error1(PaStream *stream, char* sampleBlock) {
free( sampleBlock );
exit(-1);
}
void error2(PaStream *stream, int err) {
if( stream ) {
Pa_AbortStream( stream );
Pa_CloseStream( stream );
}
Pa_Terminate();
fprintf( stderr, "An error occured while using the portaudio stream\n" );
fprintf( stderr, "Error number: %d\n", err );
fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
exit(-1);
}

Answer 1

I found that you can use the webrtc library for this as well. It comes with noise suppression which is handy. I don't understand what compression_gain_db and target_level_dbfs actually do, but setting them to their highest values seems to apply the most gain. Working in int16 as suggested by #alexander resolved many issues to my custom solution and fixing up the loop to go over the entire buffer helped as well. Both webrtc's solution and my own can be played with in realtime with the following example code.
Code example included below.
$ ./main.exe -h
-h : show this help message
-i <int> : select the INPUT DEVICE by id
-o <int> : select the OUPUT DEVICE by id
-c <int [0,90]> : compression_gain_db
-t <int [0, 31]> : target_level_dbfs
-g <0 or 1> : toggle webrtc gain control on and off (1 by default)
-k <0 or 1> : toggle custom gain control on and off (1 by default)
-f <int [1, maxInt]> : customGainControlFactor
-q <int [0, 3]> : webrtc noise supression level, high is more suppression
-e <0 or 1> : toggle webrtc noise suppression on and off (1 by default)
-d : list devices
Real time controls:
compression_gain_db UP_KEY='a' DOWN_KEY='s'
target_dbfs_level UP_KEY='d' DOWN_KEY='f'
webrtcGainControlEnabled TOGGLE_KEY='g'
webrtcNoiseSuppressionLevel UP_KEY='q' DOWN_KEY='w'
webrtcNoiseSuppressionEnabled TOGGLE_KEY='e'
customGainFactor UP_KEY='h' DOWN_KEY='j'
customGainFactorEnabled TOGGLE_KEY='k'
Press any key to close
Dependencies: tinycon, PortAudio, libwebrtc-audio-processing-devel
Note: I'm working on cygwin, if you have trouble with libwebrtc see here
Compiling: g++ main.cpp tinycon.cpp -o main -L./ -lcygportaudio-2 -lrt -lm -pthread -I/usr/include/webrtc_audio_processing/ -DWEBRTC_WIN -DWEBRTC
main.cpp
#include "portaudio.h"
#include <iostream>
#include <limits>
#include <chrono>
#include <thread>
#include <mutex>
#include "tinycon.h"
#include "webrtc/modules/audio_processing/include/audio_processing.h"
#include "webrtc/modules/interface/module_common_types.h"
#include "webrtc/system_wrappers/include/trace.h"
using webrtc::AudioProcessing;
using webrtc::AudioFrame;
using webrtc::GainControl;
using webrtc::NoiseSuppression;
#define SAMPLE_RATE (32000)
#define FRAMES_PER_BUFFER (320)
#define DITHER_FLAG (0)
#define PA_SAMPLE_TYPE paInt16
#define SAMPLE_SIZE (2)
#define SAMPLE_SILENCE (0)
#define PRINTF_S_FORMAT "%d"
/*******************************************************************/
int customGainFactor = 1;
int customGainFactorStep = 1;
bool customGainControlEnabled = true;
int compression_gain_db = 1;
int compression_gain_dbStep = 1;
int target_level_dbfs = 1;
int target_level_dbfsStep = 1;
bool webrtcGainControlEnabled = true;
bool webrtcNoiseSuppressionEnabled = true;
int webrtcNoiseSuppressionLevel = 1;
int main(int argc, char **argv);
int xrun(PaStream *stream, int err, char* sampleBlock);
void error1(PaStream *stream, char* sampleBlock);
void error2(PaStream *stream, int err);
void listDevices();
webrtc::NoiseSuppression::Level webrtcNoiseSuppressionLevelToEnum(int level);
// Use tinycon and a second thread for non blocking input
class tcon : public tinyConsole
{
public:
tcon (std::string s): tinyConsole(s) {;}
int hotkeys(char c)
{
if (c == 'a') {
if (compression_gain_db >= (0+compression_gain_dbStep)) {
compression_gain_db -= compression_gain_dbStep;
}
printf( "Compression_gain_db: %d\n", compression_gain_db );
return 1;
}
if (c == 's') {
if (compression_gain_db <= (90-compression_gain_dbStep)) {
compression_gain_db += compression_gain_dbStep;
}
printf( "Compression_gain_db: %d\n", compression_gain_db );
return 1;
}
if (c == 'd') {
if (target_level_dbfs >= (0+target_level_dbfsStep)) {
target_level_dbfs -= target_level_dbfsStep;
}
printf( "target_level_dbfs: %d\n", target_level_dbfs );
return 1;
}
if (c == 'f') {
if (target_level_dbfs <= (31-target_level_dbfsStep)) {
target_level_dbfs += target_level_dbfsStep;
}
printf( "target_level_dbfs: %d\n", target_level_dbfs );
return 1;
}
if (c == 'g') {
webrtcGainControlEnabled = !webrtcGainControlEnabled;
printf("webrtcGainControlEnabled: %s\n", (webrtcGainControlEnabled) ? "true" : "false");
return 1;
}
if (c == 'h') {
if (customGainFactor >= (1+customGainFactorStep)) {
customGainFactor -= customGainFactorStep;
}
printf( "customGainFactor: %d\n", customGainFactor );
return 1;
}
if (c == 'j') {
customGainFactor += customGainFactorStep;
printf( "customGainFactor: %d\n", customGainFactor );
return 1;
}
if (c == 'k') {
customGainControlEnabled = !customGainControlEnabled;
printf("customGainControlEnabled: %s\n", (customGainControlEnabled) ? "true" : "false");
return 1;
}
if (c == 'q') {
if (webrtcNoiseSuppressionLevel <= (3-1)) {
webrtcNoiseSuppressionLevel += 1;
}
printf( "webrtcNoiseSuppressionLevel: %d\n", webrtcNoiseSuppressionLevel );
return 1;
}
if (c == 'w') {
if (webrtcNoiseSuppressionLevel >= (0+1)) {
webrtcNoiseSuppressionLevel -= 1;
}
printf( "webrtcNoiseSuppressionLevel: %d\n", webrtcNoiseSuppressionLevel );
return 1;
}
if (c == 'e') {
webrtcNoiseSuppressionEnabled = !webrtcNoiseSuppressionEnabled;
printf("webrtcNoiseSuppressionEnabled: %s\n", (webrtcNoiseSuppressionEnabled) ? "true" : "false");
return 1;
}
return 0;
}
};
int inputThread() {
tcon tc (std::string(""));
tc.run();
}
void listDevices() {
int i, numDevices, defaultDisplayed;
const PaDeviceInfo *deviceInfo;
Pa_Initialize();
numDevices = Pa_GetDeviceCount();
printf( "Number of devices = %d\n", numDevices );
int isInputDevice = 0;
for( i=0; i<numDevices; i++ )
{
deviceInfo = Pa_GetDeviceInfo( i );
int isInputDevice = (deviceInfo->maxInputChannels > 0);
printf( "%sDeviceID: %d, Name: %s\n", (isInputDevice ? "Input" : "Output"), i, deviceInfo->name);
}
fprintf (stderr, "Press any key to close\n");
getch();
}
int main (int argc, char **argv)
{
int c;
int inputDeviceId = -1;
int outputDeviceId = -1;
opterr = 0;
const char* helpMessage =
"-h : show this help message\n"
"-i <int> : select the INPUT DEVICE by id\n"
"-o <int> : select the OUPUT DEVICE by id\n"
"-c <int [0,90]> : compression_gain_db\n"
"-t <int [0, 31]> : target_level_dbfs\n"
"-g <0 or 1> : toggle webrtc gain control on and off (1 by default)\n"
"-k <0 or 1> : toggle custom gain control on and off (1 by default)\n"
"-f <int [1, maxInt]> : customGainControlFactor\n"
"-q <int [0, 5]> : webrtc noise supression level, high is more suppression\n"
"-e <0 or 1> : toggle webrtc noise suppression on and off (1 by default)\n"
"-d : list devices\n"
"\n"
"Real time controls:\n"
"compression_gain_db UP_KEY='a' DOWN_KEY='s'\n"
"target_dbfs_level UP_KEY='d' DOWN_KEY='f'\n"
"webrtcGainControlEnabled TOGGLE_KEY='g'\n"
"webrtcNoiseSuppressionLevel UP_KEY='q' DOWN_KEY='w'\n"
"webrtcNoiseSuppressionEnabled TOGGLE_KEY='e'\n"
"customGainFactor UP_KEY='h' DOWN_KEY='j'\n"
"customGainFactorEnabled TOGGLE_KEY='k'\n";
while ((c = getopt (argc, argv, "i:o:c:t:g:k:f:w:q:hd")) != -1) {
switch (c) {
case 'i':
inputDeviceId = atoi(optarg);
break;
case 'o':
outputDeviceId = atoi(optarg);
break;
case 'c':
compression_gain_db = atoi(optarg);
break;
case 't':
target_level_dbfs = atoi(optarg);
break;
case 'g':
webrtcGainControlEnabled = (atoi(optarg) == 1) ? true : false;
break;
case 'f':
customGainFactor = atoi(optarg);
break;
case 'k':
customGainControlEnabled = (atoi(optarg) == 1) ? true : false;
break;
case 'w':
webrtcNoiseSuppressionLevel = atoi(optarg);
break;
case 'e':
webrtcNoiseSuppressionEnabled = (atoi(optarg) == 1) ? true : false;
break;
case 'd':
listDevices();
return 0;
case '?':
if (isprint (optopt))
fprintf (stderr, "Unknown option `-%c'.\n", optopt);
else
fprintf (stderr, "Unknown option character `\\x%x'.\n", optopt);
case 'h':
fprintf (stderr, helpMessage);
fprintf (stderr, "Press any key to close\n");
getch();
return 1;
default:
abort ();
}
}
// Start non blocking input thread
std::thread nonBlockingInputThread(inputThread);
PaStreamParameters inputParameters, outputParameters;
PaStream *stream = NULL;
PaError err;
const PaDeviceInfo* inputInfo;
const PaDeviceInfo* outputInfo;
char *sampleBlock = NULL;
int i;
int numBytes;
int numChannels;
err = Pa_Initialize();
if( err != paNoError ) error2(stream, err);
inputParameters.device = (inputDeviceId == -1) ? Pa_GetDefaultInputDevice() : inputDeviceId; /* default input device */
inputInfo = Pa_GetDeviceInfo( inputParameters.device );
outputParameters.device = (outputDeviceId == -1) ? Pa_GetDefaultOutputDevice() : outputDeviceId; /* default output device */
outputInfo = Pa_GetDeviceInfo( outputParameters.device );
numChannels = inputInfo->maxInputChannels < outputInfo->maxOutputChannels
? inputInfo->maxInputChannels : outputInfo->maxOutputChannels;
inputParameters.channelCount = numChannels;
inputParameters.sampleFormat = PA_SAMPLE_TYPE;
inputParameters.suggestedLatency = inputInfo->defaultHighInputLatency ;
inputParameters.hostApiSpecificStreamInfo = NULL;
printf( "Input device # %d.\n", inputParameters.device );
printf( " Name: %s\n", inputInfo->name );
outputParameters.channelCount = numChannels;
outputParameters.sampleFormat = PA_SAMPLE_TYPE;
outputParameters.suggestedLatency = outputInfo->defaultHighOutputLatency;
outputParameters.hostApiSpecificStreamInfo = NULL;
printf( "Output device # %d.\n", outputParameters.device );
printf( " Name: %s\n", outputInfo->name );
/* -- setup -- */
err = Pa_OpenStream(
&stream,
&inputParameters,
&outputParameters,
SAMPLE_RATE,
FRAMES_PER_BUFFER,
paClipOff, /* we won't output out of range samples so don't bother clipping them */
NULL, /* no callback, use blocking API */
NULL ); /* no callback, so no callback userData */
if( err != paNoError ) error2(stream, err);
numBytes = FRAMES_PER_BUFFER * numChannels * SAMPLE_SIZE ;
sampleBlock = (char *) malloc( numBytes );
if( sampleBlock == NULL )
{
printf("Could not allocate record array.\n");
error1(stream, sampleBlock);
}
// Configure webrtc::audioprocessing
int webrtcErr;
AudioProcessing* apm = AudioProcessing::Create();
apm->high_pass_filter()->Enable(true);
apm->noise_suppression()->set_level(webrtcNoiseSuppressionLevelToEnum(webrtcNoiseSuppressionLevel));
apm->noise_suppression()->Enable(webrtcNoiseSuppressionEnabled);
apm->gain_control()->set_mode(apm->gain_control()->kFixedDigital);
apm->gain_control()->set_compression_gain_db(compression_gain_db);
apm->gain_control()->set_target_level_dbfs(target_level_dbfs);
apm->gain_control()->Enable(webrtcGainControlEnabled);
err = Pa_StartStream( stream );
if( err != paNoError ) error1(stream, sampleBlock);
while (1) {
// You may get underruns or overruns if the output is not primed by PortAudio.
err = Pa_ReadStream( stream, sampleBlock, FRAMES_PER_BUFFER );
if( err ) xrun(stream, err, sampleBlock);
// Run custom gain solution
if (customGainControlEnabled) {
int blockIndex;
short* sampleBlockShort = (short*)sampleBlock;
for (blockIndex = 0; blockIndex < FRAMES_PER_BUFFER*numChannels; blockIndex++) {
int iSample = (int)sampleBlockShort[blockIndex];
iSample *= customGainFactor;
if (iSample > std::numeric_limits<short>::max())
iSample =
(iSample > std::numeric_limits<short>::max()) ? std::numeric_limits<short>::max()
: (iSample < std::numeric_limits<short>::min()) ? std::numeric_limits<short>::min()
: iSample;
sampleBlockShort[blockIndex] = (short)iSample;
}
}
// Apply webrtc gain and noise suppression
apm->noise_suppression()->set_level(webrtcNoiseSuppressionLevelToEnum(webrtcNoiseSuppressionLevel));
apm->noise_suppression()->Enable(webrtcNoiseSuppressionEnabled);
apm->gain_control()->set_compression_gain_db(compression_gain_db);
apm->gain_control()->set_target_level_dbfs(target_level_dbfs);
apm->gain_control()->Enable(webrtcGainControlEnabled);
webrtc::AudioFrame frame;
frame.num_channels_ = numChannels;
frame.sample_rate_hz_ = SAMPLE_RATE;
frame.samples_per_channel_ = FRAMES_PER_BUFFER;
memcpy(frame.data_, sampleBlock, numBytes);
if ((webrtcErr = apm->ProcessStream(&frame)) < 0) {
printf("Error Code: %d\n", webrtcErr); fflush(stdout);
return -1;
}
memcpy(sampleBlock, frame.data_, numBytes);
err = Pa_WriteStream( stream, sampleBlock, FRAMES_PER_BUFFER );
if( err ) xrun(stream, err, sampleBlock);
}
printf("Wire off.\n"); fflush(stdout);
err = Pa_StopStream( stream );
if( err != paNoError ) error1(stream, sampleBlock);
free( sampleBlock );
Pa_Terminate();
return 0;
}
int xrun(PaStream *stream, int err, char* sampleBlock) {
printf("err = %d\n", err); fflush(stdout);
if( stream ) {
Pa_AbortStream( stream );
Pa_CloseStream( stream );
}
free( sampleBlock );
Pa_Terminate();
if( err & paInputOverflow )
fprintf( stderr, "Input Overflow.\n" );
if( err & paOutputUnderflow )
fprintf( stderr, "Output Underflow.\n" );
return -2;
}
void error1(PaStream *stream, char* sampleBlock) {
free( sampleBlock );
exit(-1);
}
void error2(PaStream *stream, int err) {
if( stream ) {
Pa_AbortStream( stream );
Pa_CloseStream( stream );
}
Pa_Terminate();
fprintf( stderr, "An error occured while using the portaudio stream\n" );
fprintf( stderr, "Error number: %d\n", err );
fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
exit(-1);
}
webrtc::NoiseSuppression::Level webrtcNoiseSuppressionLevelToEnum(int level) {
switch (level) {
case 0 : return webrtc::NoiseSuppression::Level::kLow;
case 1 : return webrtc::NoiseSuppression::Level::kModerate;
case 2 : return webrtc::NoiseSuppression::Level::kHigh;
case 3 : return webrtc::NoiseSuppression::Level::kVeryHigh;
}
}