sound wave sawtooth in c

Question

I'm trying to generate sawtooth wave in c. I'm so close to the end of my work but I have problem which must be resolved. I attached clode below.

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <tgmath.h>

/******************************
*  Magic file format strings. *
******************************/
const char fChunkID[]     = {'R', 'I', 'F', 'F'};
const char fFormat[]      = {'W', 'A', 'V', 'E'};
const char fSubchunk1ID[] = {'f', 'm', 't', ' '};
const char fSubchunk2ID[] = {'d', 'a', 't', 'a'};

/********************************
* WriteWavePCM() configuration: *
* - 2 channels,                 *
* - frequency 44100 Hz.         *
********************************/
const unsigned short N_CHANNELS = 2;
const unsigned int SAMPLE_RATE = 48000;
const unsigned short BITS_PER_BYTE = 8;

bool WriteWavePCM(short* sound, size_t pairAmount, char* fileName){
    const static unsigned int fSubchunk1Size = 16;
    const static unsigned short fAudioFormat = 1;
    const static unsigned short fBitsPerSample = 16;

    unsigned int fByteRate = SAMPLE_RATE * N_CHANNELS * fBitsPerSample / BITS_PER_BYTE;

    unsigned short fBlockAlign = N_CHANNELS * fBitsPerSample / BITS_PER_BYTE;
    unsigned int fSubchunk2Size;
    unsigned int fChunkSize;

    FILE* fout;
    size_t ws;

    if (!sound || !fileName || !(fout = fopen( fileName, "w" ))) return false;

    fSubchunk2Size = pairAmount * N_CHANNELS * fBitsPerSample / BITS_PER_BYTE;
    fChunkSize = 36 + fSubchunk2Size;

    // Writing the RIFF header:
    fwrite(&fChunkID, 1, sizeof(fChunkID),      fout);
    fwrite(&fChunkSize,  sizeof(fChunkSize), 1, fout);
    fwrite(&fFormat, 1,  sizeof(fFormat),       fout);

    // "fmt" chunk:
    fwrite(&fSubchunk1ID, 1, sizeof(fSubchunk1ID),      fout);
    fwrite(&fSubchunk1Size,  sizeof(fSubchunk1Size), 1, fout);
    fwrite(&fAudioFormat,    sizeof(fAudioFormat),   1, fout);
    fwrite(&N_CHANNELS,      sizeof(N_CHANNELS),     1, fout);
    fwrite(&SAMPLE_RATE,     sizeof(SAMPLE_RATE),    1, fout);
    fwrite(&fByteRate,       sizeof(fByteRate),      1, fout);
    fwrite(&fBlockAlign,     sizeof(fBlockAlign),    1, fout);
    fwrite(&fBitsPerSample,  sizeof(fBitsPerSample), 1, fout);

    /* "data" chunk: */
    fwrite(&fSubchunk2ID, 1, sizeof(fSubchunk2ID),      fout);
    fwrite(&fSubchunk2Size,  sizeof(fSubchunk2Size), 1, fout);

    /* sound data: */
    ws = fwrite(sound, sizeof(short), pairAmount * N_CHANNELS, fout);
    fclose(fout);
    return true;
}

////////////////////////////////////////////////

const unsigned int N_SAMPLE_PAIRS = 50000;

int main(int argc, char* argv[]){
    short* sound;
    int i;
    int j;
    bool status;
    char* file_name;
    int l; // dodane

    sound = (int*) malloc(sizeof(int) * N_SAMPLE_PAIRS * N_CHANNELS );

    if (!sound)
    {
        puts("Could not allocate space for the sound data.");
        return (EXIT_FAILURE);
    }

    int amplitude = 10000;
    int frequency = 80;
    short record = 0;
    short waveNumber = 1;
    int samplesPerWavelength = SAMPLE_RATE / (frequency/N_CHANNELS);
    int soundLen = 10 * samplesPerWavelength;
    int ampStep = (int)((amplitude*2)/(int)samplesPerWavelength);
    short step = 5*samplesPerWavelength;
    short muteRate = amplitude/(soundLen/samplesPerWavelength);
    int totalSamplesWritten = 0;
    int tempSample =0;

    for (i=0, j=0; i<N_SAMPLE_PAIRS*N_CHANNELS; i+=2, j++) {
        ampStep = (int)((amplitude*2)/(int)samplesPerWavelength);
        tempSample = (int)((totalSamplesWritten%samplesPerWavelength)*ampStep);
        sound[i] = tempSample;
        sound[i+1] = tempSample;
        totalSamplesWritten++;
    }


    file_name = argc > 1 ? argv[1] : "Default2.wav";
    status = WriteWavePCM(sound, N_SAMPLE_PAIRS, file_name);


    free(sound);

    if (status)
    {
        printf("Discotheque is ready in \"%s\"\n", file_name);
    }
    else
    {
        puts( "Something seems to have gone wrong." );
        return (EXIT_FAILURE);
    }

    return 0;
}

Here is my result. There is sawtooth but with strange behavior. I don't know why this is there. I checked my array of samples and everything look good.

Can someone help me? I'm stuck and I don't know what to do. I checked it in 2 different programs: audiocity and wavepadaudio and in both of then, this behavior exist. So i'm problem with my code for sure. Help me please.

Answer 1

When I looked at the file dump (MSVC compilation) I noticed some 0D 0A data pairs. I then changed this

fout = fopen( fileName, "w" )

to this specifing a binary file

fout = fopen( fileName, "wb" )

and now the glitch has gone.

Note that

If tor b is not given in mode, the default translation mode is defined by the global variable _fmode.

So the default translation mode must have been "text".

Answer 2

Here are some screen captures of the output I get. Seems fine to me.

Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-pc-cygwin/5.4.0/lto-wrapper.exe Target: i686-pc-cygwin Configured with: /cygdrive/i/szsz/tmpp/gcc/gcc-5.4.0-1.i686/src/gcc-5.4.0/configure --srcdir=/cygdrive/i/szsz/tmpp/gcc/gcc-5.4.0-1.i686/src/ gcc-5.4.0 --prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc --docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/h tml -C --build=i686-pc-cygwin --host=i686-pc-cygwin --target=i686-pc-cygwin --without-libiconv-prefix --without-libintl-prefix --libexecdir= /usr/lib --enable-shared --enable-shared-libgcc --enable-static --enable-version-specific-runtime-libs --enable-bootstrap --enable-__cxa_ate xit --with-dwarf2 --with-arch=i686 --with-tune=generic --disable-sjlj-exceptions --enable-languages=ada,c,c++,fortran,java,lto,objc,obj-c++ --enable-graphite --enable-threads=posix --enable-libatomic --enable-libcilkrts --enable-libgomp --enable-libitm --enable-libquadmath --enab le-libquadmath-support --enable-libssp --enable-libada --enable-libjava --enable-libgcj-sublibs --disable-java-awt --disable-symvers --with- ecj-jar=/usr/share/java/ecj.jar --with-gnu-ld --with-gnu-as --with-cloog-include=/usr/include/cloog-isl --without-libiconv-prefix --without- libintl-prefix --with-system-zlib --enable-linker-build-id --with-default-libstdcxx-abi=gcc4-compatible Thread model: posix gcc version 5.4.0 (GCC)

uname -a CYGWIN_NT-6.1-WOW DE-E03895 2.8.0(0.309/5/3) 2017-04-01 20:42 i686 Cygwin

Here's a screen shot of the corrupted samples in your output;