Incorrect audio data when saving wav file using C++ (based on a C# program)

Question

I wrote a C# function to save audio data, which worked without any problems. Here is the original function used to write the data to a stream:

public override void store(double data)
// stores a sample in the stream
{
    double sample_l;
    short sl;
    sample_l = data * 32767.0f;
    sl = (short)sample_l;
    stream.WriteByte((byte)(sl & 0xff));
    stream.WriteByte((byte)(sl >> 8));
    stream.WriteByte((byte)(sl & 0xff));
    stream.WriteByte((byte)(sl >> 8));
}

I converted this to some C++ code and used it to output data to a wav file:

double data;
short smp;
char b1, b2;
int i;
std::ofstream sfile(fname);
...
for (i = 0; i < tot_smps; i++)
{
    smp = (short)(rend() * 32767.0);
    b1 = smp & 0xff;
    b2 = smp >> 8;
    sfile.write((char*)&b1, sizeof(char));
    sfile.write((char*)&b2, sizeof(char));
    sfile.write((char*)&b1, sizeof(char));
    sfile.write((char*)&b2, sizeof(char));
}

rend is always between -1 and 1. When I listen to / look at the wav file from the C++ program there is an extra buzzing sound. There seems to be something different about the data conversion in the C++ code compared to the original C# code, resulting in different data / sound being outputted by the two different programs.

Answer 1

By default when you open a stream in C++ it's opened in text mode , which can do things like converting certain character sequences to others (most notably 0x0a can become 0x0d 0x0a ( '\\n' to "\\r\\n" )).

You need to open the stream in binary mode:

std::ofstream sfile(fname, std::ios::out | std::ios::binary);