c++ applying FFT to wav file data

Question

This is my first time working with wav files and fft alike. Given the following code:

    char* loadWAV(const char* fn, int& chan, int& samplerate, int& bps, int& size){
        char buffer[4];
        ifstream in(fn, ios::binary);
        in.read(buffer, 4);                                                             //ChunkID "RIFF"
        if(strncmp(buffer, "RIFF", 4) != 0){ 
                cerr << "this is not a valid wave file";
                return NULL;
        }   
        in.read(buffer,4);                                                              //ChunkSize 
        in.read(buffer,4);                                                              //Format "WAVE"
        in.read(buffer,4);                                                              // "fmt "
        in.read(buffer,4);                                                              // 16
        in.read(buffer,2);                                                              // 1
        in.read(buffer,2);                                                              // NUMBER OF CHANNELS
        chan = convertToInt(buffer,2);
        in.read(buffer,4);                                                              // SAMPLE RATE
        samplerate = convertToInt(buffer,4);
        in.read(buffer,4);                                                              // ByteRate
        in.read(buffer,2);                                                              // BlockAlign
        in.read(buffer,2);                                                              // bits per sample
        bps = convertToInt(buffer,2);
        in.read(buffer,4);                                                              // "data"
        in.read(buffer,4);
        size = convertToInt(buffer,4);
        char * data = new char[size];
        in.read(data,size);
        return data;
}

I'm assuming data pointer contains the information I need, but I don't know how to discern this information. I'm using this as a reference but I don't know what to make of the "right channel left channel" aspect and how to prepare this data to be used in an FFT. If you have any references to good documentation about this I appreciate it, My search efforts have so far resulted in NILL.

edit: also If anyone could point me to a good guide to operating with wav format files on this level i would greatly appreciate it. Thank you in advance.

Answer 1

The data you have is in PCM packets.

Try these questions as a starting point:

• How is audio represented with numbers?
• How do you analyse the fundamental frequency of a PCM or WAV sample?
• Detect a specific frequency/tone from raw wave-data .

For the FFT part of your question, you may want to consider https://dsp.stackexchange.com/.