Opus, can't encode / decode all data - c++

Question

I'm working using Opus to encode and decode some Portaudio recorded data, so i'm trying to encode a record of around 10 seconds, i've wrote the registered data to a log file and i get around 480000 lines which represent the NUM_SECONDS * SAMPLE_rate, so the time * the frequency.
Problem is when i try to use opus with it, i can encode and decode, but the size of the data returned is not the same at all, it is the FRAMES_PER_BUFFER size, and the data itself does not correspond to anything from the previous data. Here is my code :
my encode and decode methods :
typedef struct {
int size;
std::vector<unsigned char> *sound;
} AudioEnc;
typedef struct {
int size;
std::vector<float> sound;
} AudioData;
#define SAMPLE_RATE (48000)
#define FRAMES_PER_BUFFER (1920)
#define NUM_SECONDS (10)
#define NUM_CHANNELS (1)
AudioEnc &Opus::Encode(AudioData &data)
{
AudioEnc enc;
enc.sound = new std::vector<unsigned char>;
const unsigned int max_size = NUM_SECONDS * SAMPLE_RATE * sizeof(float);
float sound[max_size];
enc.sound->resize(NUM_SECONDS * SAMPLE_RATE);
if (data.size == 0)
enc.sound->resize(opus_encode_float(_encode, sound, FRAMES_PER_BUFFER, enc.sound->data(), max_size));
else
enc.sound->resize(opus_encode_float(_encode, data.sound.data(), FRAMES_PER_BUFFER, enc.sound->data(), max_size));
return (enc);
}
AudioData Opus::Decode(AudioEnc &data)
{
AudioData dec;
dec.sound.resize(NUM_SECONDS * SAMPLE_RATE);
dec.sound.resize(opus_decode_float(_decode, data.sound->data(), data.sound->size(), dec.sound.data(), FRAMES_PER_BUFFER, 0));
return (dec);
}
Record data is to big for pastebin, do you guys have any idea on what i'm missing ?