spectrum.cpp

Go to the documentation of this file.

 
#include "sigpack.h"
using namespace sp;
 
// Specs from http://soundfile.sapp.org/doc/WaveFormat/
typedef struct WAV_HEADER
{
    uint8_t  RIFF[4];        // RIFF Header Magic header
    uint32_t chunkSize;      // RIFF Chunk Size
    uint8_t  WAVE[4];        // WAVE Header
    uint8_t  fmt[4];         // FMT header
    uint32_t subchunk1Size;  // Size of the fmt chunk
    uint16_t audioFormat;    // Audio format
    uint16_t numOfChan;      // Number of channels
    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
    uint8_t  subchunk2ID[4]; // "data"  string
    uint32_t subchunk2Size;  // Sampled data length
} wav_header;
 
int main( int argc, char* argv[] )
{
    wav_header wavHeader;
 
    // Get THX DeepNote .wav file at
    // http://www.orangefreesounds.com/wp-content/uploads/Zip/thx-sound-test.zip
    const char* filename = "thx-sound-test.wav";
    FILE* wavFile = fopen( filename, "r" );
    if (wavFile == nullptr)
    {
        fprintf(stderr, "Error: Failed to open file '%s'\n", filename);
        fprintf(stderr, "Download it at http://www.orangefreesounds.com/wp-content/uploads/Zip/thx-sound-test.zip");
        return 1;
    }
    // Read the header
    fread( &wavHeader, 1, sizeof( wav_header ), wavFile );
 
    // Read the data
    uint16_t Nb = wavHeader.bitsPerSample / 8;       // Number of bytes per sample
    uint32_t Ns = ( wavHeader.chunkSize - 36 ) / Nb; // Number of samples
 
    arma::Mat<int16_t> x( wavHeader.numOfChan, Ns / wavHeader.numOfChan );
    fread( x.memptr(), Nb, Ns, wavFile );
    fclose( wavFile );
 
    // Get the left channel
    arma::Col<int16_t> x_left = x.row( 0 ).t();
 
    // Calculate the spectrogram
    const int FFT_SIZE    = 1024;
    const int FFT_OVERLAP = 128;
    arma::mat P           = 10 * log10( abs( specgram( x_left, FFT_SIZE, FFT_OVERLAP ) ) );
 
    // Plot
    arma::mat Q = P.rows( FFT_SIZE / 2, FFT_SIZE - 1 ); // Cut out the positive parts
    gplot     gp0;
    gp0.window( "Deep note spectrogram", 100, 100, 1200, 400 );
    gp0.send2gp( "unset tics" );
    gp0.send2gp( "unset colorbox" );
    gp0.image( Q );
    return 0;
}