c++ - 如何使用 C++ 生成音频 wav 文件的波形

Question

我目前正在使用 C++ 来实现我的代码。这个想法是我想通过一个程序读取一个 wav 文件，然后在屏幕上输出它的波形。我已经在那里找到了一些参考资料：C++ Reading the Data part of a WAV file。这是我读取音频文件的代码。我不知道如何生成波形。

#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;
 }

标签： c++audio

Answer 1

我会将此作为带有代码要点的评论而不是答案，因为它不会直接回答您的问题，但我对此没有足够的声誉。

我做了你想要用 Qt 做的事情，我的大部分代码来自 Qt 的文档。您需要找到样本的峰值，然后绘制它。让我分享一些代码，这些代码可以让您了解您可能想要如何做到这一点。

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;
}

对于 Qt 中的绘图部分（可能对您没有用）

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;
}