Converting raw byte data to float[]

Question

I have this code for converting a byte[] to float[].

public float[] ConvertByteToFloat(byte[] array)
{
    float[] floatArr = new float[array.Length / sizeof(float)];
    int index = 0;
    for (int i = 0; i < floatArr.Length; i++)
    {
        floatArr[i] = BitConverter.ToSingle(array, index);
        index += sizeof(float);
    }
    return floatArr;
}

Problem is, I usually get a NaN result! Why should this be? I checked if there is data in the byte[] and the data seems to be fine. If it helps, an example of the values are:

new byte[] {
    231,
    255,
    235,
    255,
}

But this returns NaN (Not a Number) after conversion to float. What could be the problem? Are there other better ways of converting byte[] to float[]? I am sure that the values read into the buffer are correct since I compared it with my other program (which performs amplification for a .wav file).

Answer 1

If endianness is the problem, you should check the value of BitConverter.IsLittleEndian to determine if the bytes have to be reversed:

public static float[] ConvertByteToFloat(byte[] array) {
  float[] floatArr = new float[array.Length / 4];
  for (int i = 0; i < floatArr.Length; i++) {
    if (BitConverter.IsLittleEndian) {
      Array.Reverse(array, i * 4, 4);
    }
    floatArr[i] = BitConverter.ToSingle(array, i * 4);
  }
  return floatArr;
}

Answer 2

Isn't the problem that the 255 in the exponent represents NaN (see Wikipedia in the exponent section), so you should get a NaN. Try changing the last 255 to something else...