How to generate a waveform of audio wav file using C++ - c++

Question

I am currently using the C++ to implement my code. The idea is I want to read a wav file through a program and then output its waveform on the screen. I have already found some references there:C++ Reading the Data part of a WAV file. and here is my code of reading the audio file. I have no idea of how to generate the waveform .
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
using std::string;
using std::fstream;
typedef struct WAV_HEADER
{
/* for the part of RIEF Chunk Descriptor */
uint8_t RIFF[4]; // RIFF Header Magic header
uint32_t ChunkSize; // RIFF Chunk Size
uint8_t WAVE[4]; // WAVE Header
/* for the part of "fmt" subChunk */
uint8_t fmt[4]; // FMT header
uint32_t Subchunk1Size; // Size of the fmt chunk
uint16_t AudioFormat; // Audio format 1=PCM,6=mulaw,7=alaw, 257=IBM Mu-Law, 258=IBM A-Law, 259=ADPCM
uint16_t NumOfChan; // Number of channels 1=Mono 2=Sterio
uint32_t SamplesPerSec; // Sampling Frequency in Hz
uint32_t bytesPerSec; // bytes per second
uint16_t blockAlign; // 2=16-bit mono, 4=16-bit stereo
uint16_t bitsPerSample; // Number of bits per sample
/* For the part of "data" subChunk */
uint8_t Subchunk2ID[4]; // "data" string
uint32_t Subchunk2Size; // Sampled data length
}wav_hdr;
int getFileSize(FILE* inFile);
int main(int argc, char* argv[])
{
wav_hdr wavHeader;
int headerSize = sizeof(wav_hdr), filelength = 0;
const char* filePath;
string input;
if (argc <= 1)
{
cout << "Input wave file name: ";
cin >> input;
cin.get();
filePath = input.c_str();
}
else
{
filePath = argv[1];
cout << "Input wave file name: " << filePath << endl;
}
FILE* wavFile = fopen(filePath, "r");
if (wavFile == nullptr)
{
fprintf(stderr, "Unable to open wave file: %s\n", filePath);
return 1;
}
//Read the header
size_t bytesRead = fread(&wavHeader, 1, headerSize, wavFile);
cout << "Header Read " << bytesRead << " bytes." << endl;
if (bytesRead > 0)
{
//Read the data
uint16_t bytesPerSample = wavHeader.bitsPerSample / 8; //Number of bytes per sample
uint64_t numSamples = wavHeader.ChunkSize / bytesPerSample; //How many samples are in the wav file?
static const uint16_t BUFFER_SIZE = 4096;
int8_t* buffer = new int8_t[BUFFER_SIZE];
while ((bytesRead = fread(buffer, sizeof buffer[0], BUFFER_SIZE / (sizeof buffer[0]), wavFile)) > 0)
{
/** DO SOMETHING WITH THE WAVE DATA HERE **/
cout << "Read " << bytesRead << " bytes." << endl;
}
delete [] buffer;
buffer = nullptr;
filelength = getFileSize(wavFile);
cout << "File is :" << filelength << " bytes." << endl;
cout << "RIFF header :" << wavHeader.RIFF[0] << wavHeader.RIFF[1] << wavHeader.RIFF[2] << wavHeader.RIFF[3] << endl;
cout << "WAVE header :" << wavHeader.WAVE[0] << wavHeader.WAVE[1] << wavHeader.WAVE[2] << wavHeader.WAVE[3] << endl;
cout << "FMT :" << wavHeader.fmt[0] << wavHeader.fmt[1] << wavHeader.fmt[2] << wavHeader.fmt[3] << endl;
cout << "Data size :" << wavHeader.ChunkSize << endl;
// Display the sampling Rate from the header
cout << "Sampling Rate :" << wavHeader.SamplesPerSec << endl;
cout << "Number of bits used :" << wavHeader.bitsPerSample << endl;
cout << "Number of channels :" << wavHeader.NumOfChan << endl;
cout << "Number of bytes per second :" << wavHeader.bytesPerSec << endl;
cout << "Data length :" << wavHeader.Subchunk2Size << endl;
cout << "Audio Format :" << wavHeader.AudioFormat << endl;
// Audio format 1=PCM,6=mulaw,7=alaw, 257=IBM Mu-Law, 258=IBM A-Law, 259=ADPCM
cout << "Block align :" << wavHeader.blockAlign << endl;
cout << "Data string :" << wavHeader.Subchunk2ID[0] << wavHeader.Subchunk2ID[1] << wavHeader.Subchunk2ID[2] << wavHeader.Subchunk2ID[3] << endl;
}
fclose(wavFile);
return 0;
}
// find the file size
int getFileSize(FILE* inFile)
{
int fileSize = 0;
fseek(inFile, 0, SEEK_END);
fileSize = ftell(inFile);
fseek(inFile, 0, SEEK_SET);
return fileSize;
}

Answer 1

I would have left this as a comment with code gists and not an answer since it doesn't answer your question directly but I don't have enough reputation for this.
I did what you're trying to do with Qt, most of my code comes from Qt's documentation. You need to find the peak value of the samples and then draw that. Let me share some code that could give you an idea on how you might want to do it.
void Waveform::appendSamples()
{
buffer = audioDecoder->read();
qreal peak = getPeakValue(buffer.format());
const qint16 *data = buffer.constData<qint16>();
int count = buffer.sampleCount() / 2;
for (int i = 0; i < count; i += 1200){ // I want 40 samples per second currently assuming 48kHz
double val = data[i]/peak;
samples.append(val * 300); // *300 for scaling
}
}
qreal Waveform::getPeakValue(const QAudioFormat &format)
{
qreal ret(0);
if (format.isValid()){
switch (format.sampleType()) {
case QAudioFormat::Unknown:
break;
case QAudioFormat::Float:
if (format.sampleSize() != 32)
ret = 0;
else
ret = 1.00003;
break;
case QAudioFormat::SignedInt:
if (format.sampleSize() == 32)
ret = INT_MAX;
else if (format.sampleSize() == 16)
ret = SHRT_MAX;
else if (format.sampleSize() == 8)
ret = CHAR_MAX;
break;
case QAudioFormat::UnSignedInt:
if (format.sampleSize() == 32)
ret = UINT_MAX;
else if (format.sampleSize() == 16)
ret = USHRT_MAX;
else if (format.sampleSize() == 8)
ret = UCHAR_MAX;
break;
default:
break;
}
}
return ret;
}
For the drawing part in Qt (probably not useful to you)
QSGNode* WaveformRenderer::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
{
QSGSimpleRectNode *n = static_cast<QSGSimpleRectNode *>(oldNode);
if(!n){
n = new QSGSimpleRectNode();
n->setColor(Qt::red);
}
QVector<double> samples = wav->getSamples(); //retrieve the samples
int numberOfSamples = samples.size();
setItemWidth(qreal(numberOfSamples * 2)); //signal stuff for qml
for(int i = 0; i < numberOfSamples; ++i){
QSGSimpleRectNode *temp = new QSGSimpleRectNode();
temp->setColor(Qt::green);
temp->setRect(i * 2, height()/2 - samples[i], 2, samples[i] * 2);
n->appendChildNode(temp);
}
return n;
}