u-law compression returns invalid file c++ - c++

Question

I'm trying to apply the u-law algorithm to a wav file file.wav, and then create a new file file2.wav.
file.wav has 16 bits/sample, and I want to obtain a file2.wav that has 8 bits/sample.
This is my code:
#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
using std::string;
using std::fstream;
typedef struct WAV_HEADER {
char RIFF[4];
unsigned long ChunkSize;
char WAVE[4];
char fmt[4];
unsigned long Subchunk1Size;
unsigned short AudioFormat;
unsigned short NumOfChan;
unsigned long SamplesPerSec;
unsigned long bytesPerSec;
unsigned short blockAlign;
unsigned short bitsPerSample;
char Subchunk2ID[4];
unsigned long Subchunk2Size;
} wav_hdr;
int headerSize = 0;
string path = "file.wav";
wav_hdr wavHeader;
FILE* openFile() {
const char* filePath;
FILE *wavFile;
headerSize = sizeof(wav_hdr);
filePath = path.c_str();
wavFile = fopen(filePath, "rb");
if (wavFile == NULL) {
printf("Error\n");
}
fread(&wavHeader, headerSize, 1, wavFile);
return wavFile;
}
int8_t MuLaw_Encode(int16_t number)
{
const uint16_t MULAW_MAX = 0x1FFF;
const uint16_t MULAW_BIAS = 33;
uint16_t mask = 0x1000;
uint8_t sign = 0;
uint8_t position = 12;
uint8_t lsb = 0;
if (number < 0)
{
number = -number;
sign = 0x80;
}
number += MULAW_BIAS;
if (number > MULAW_MAX)
{
number = MULAW_MAX;
}
for (; ((number & mask) != mask && position >= 5); mask >>= 1, position--)
;
lsb = (number >> (position - 4)) & 0x0f;
return (~(sign | ((position - 5) << 4) | lsb));
}
int fileSize(FILE *file) {
int fileSize = 0;
fseek(file, 0, SEEK_END);
fileSize = ftell(file);
fseek(file, 0, SEEK_SET);
return fileSize;
}
double bitsPerSample() {
double bitsPerE;
bitsPerE = wavHeader.bitsPerSample;
return bitsPerE;
}
int main() {
FILE *wavFile;
wavFile = openFile();
FILE* fptr2;
fptr2 = fopen("file2.wav", "wb");
int samples_count = fileSize(wavFile) / bitsPerSample();
short int *value = new short int[samples_count];
for (int16_t i = 0; i < samples_count; i++)
{
fread(&value[i], samples_count, 1, wavFile);
cout << value[i] << " "; // the output is in the attached picture
MuLaw_Encode(value[i]);
}
fwrite(value, sizeof(char), samples_count, fptr2);
return 0;
}
I took the u-law algorithm from here (2.1. µ-Law Compression (Encoding) Algorithm)
Am I doing something wrong? Because I obtain a corrupt file.

Answer 1

No header is ever written to the result file, so the first part of the data would get interpreted as a header, and it would be wrong. You can see in the file that it does not start with RIFFþR�WAVEfmt or something sufficiently similar.
The data written to the result file is value, the original data read from the input file, not the µ-law encoded data (which is only cout'ed and not saved).
The loop that reads the samples reads some wrong samples, because the computation of samples_count puts the current position back at the start, where the header is.