Ffmpeg mix

To realize mixing, the format of two audio streams should be ensured （ Sampling rate 、 Bit depth and number of channels ） Exactly the same , If different , You need to resample the original audio data before mixing .

ｆｆｍｐｅｇ command ：

2 individual pcm Mixing , The input and output formats are the same ：48k, Two channel ,16bit

ffmpeg -f s16le -ar 48000 -ac 2 -i 11.pcm -f s16le -ar 48000 -ac 2 -i 22.pcm -filter_complex amix=inputs=2:duration=first:dropout_transition=0 -f s16le -ar 48000 -ac 2 mix.pcm

ｃｏｄｅ：

#include <iostream>

#include <stdio.h>  
#include <stdlib.h>  
#include <math.h> 
#define IN_FILE1 "E:\\doc\\VA_tool\\11.pcm"  
#define IN_FILE2 "E:\\doc\\VA_tool\\22.pcm"  
#define OUT_FILE "E:\\doc\\VA_tool\\remix.pcm"  

#define SIZE_AUDIO_FRAME (2)  

void Mix(char sourseFile[10][SIZE_AUDIO_FRAME], int number, char* objectFile)
{
    // Normalized mixing  
    int const MAX = 32767;
    int const MIN = -32768;

    double f = 1;
    int output;
    int i = 0, j = 0;
    for (i = 0; i < SIZE_AUDIO_FRAME / 2; i++)
    {
        int temp = 0;
        for (j = 0; j < number; j++)
        {
            temp += *(short*)(sourseFile[j] + i * 2);
        }
        output = (int)(temp * f);
        if (output > MAX)
        {
            f = (double)MAX / (double)(output);
            output = MAX;
        }
        if (output < MIN)
        {
            f = (double)MIN / (double)(output);
            output = MIN;
        }
        if (f < 1)
        {
            f += ((double)1 - f) / (double)32;
        }
        *(short*)(objectFile + i * 2) = (short)output;
    }
}

int main()
{
    FILE* fp1, * fp2, * fpm;
    fopen_s(&fp1,IN_FILE1, "rb");
    fopen_s(&fp2,IN_FILE2, "rb");
    fopen_s(&fpm,OUT_FILE, "wb");

    short data1, data2, date_mix;
    int ret1, ret2;
    char sourseFile[10][2];

    while (1)
    {
        ret1 = fread(&data1, 2, 1, fp1);
        ret2 = fread(&data2, 2, 1, fp2);
        *(short*)sourseFile[0] = data1;
        *(short*)sourseFile[1] = data2;

        if (ret1 > 0 && ret2 > 0)
        {
            Mix(sourseFile, 2, (char*)&date_mix);
            /*
            if( data1 < 0 && data2 < 0)
                date_mix = data1+data2 - (data1 * data2 / -(pow(2,16-1)-1));
            else
                date_mix = data1+data2 - (data1 * data2 / (pow(2,16-1)-1));*/

            if (date_mix > pow(2, 16 - 1) || date_mix < -pow(2, 16 - 1))
                printf("mix error\n");
        }
        else if ((ret1 > 0) && (ret2 == 0))
        {
            date_mix = data1;
        }
        else if ((ret2 > 0) && (ret1 == 0))
        {
            date_mix = data2;
        }
        else if ((ret1 == 0) && (ret2 == 0))
        {
            break;
        }
        fwrite(&date_mix, 2, 1, fpm);
    }
    fclose(fp1);
    fclose(fp2);
    fclose(fpm);
    std::cout << "done!\n";
    system("pause");
    return 0;
}