Source code for: "Adding subliminal stimuli in real-time to audio recordings" (http://www.yousry.de/adding-subliminal-stimuli-in-real-time-to-audio-recordingssprachmodul-v2-0/)

subliminal stimuli demo

#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <locale.h>
#include <stdbool.h> 
#include <math.h>

#include "simpleAudio.h"

int main(int argc, char** argv)
{
    wprintf(L"Simple Audio Demo\n");

    bool sadInitOk = sad_initPulseAudio();

    if(argc != 2) {
        wprintf(L"Usage: audioDemo Ogg-file\n");
        exit(1);
    } 

    char* audiofile = argv[1]; 

    t_sad_stream *mStream = sad_getOggStream(audiofile);

    const float fortyHZ = (float)mStream->rate / 40.0f;

    int volN = 25;
    float vol[volN];
    float *volP = vol;

    __block int atLeast = 0;
    const float minDuration = 50000;


    // code injection into the stream worker. In this case pa

    sad_callbackInjector =^(pa_stream *s, size_t length, void *userdata) 
    {
        t_sad_stream* streamData = (t_sad_stream*) userdata;
        size_t remainingLength = MIN(length, streamData->size - streamData->seek);

        // short range [-32767,+32767]
        short *audioValues = (short*)mStream->data;

        const size_t seekStart = streamData->seek / sizeof(short);
        const size_t seekEnd = seekStart + remainingLength / sizeof(short);

        for(size_t i = seekStart; i < seekEnd; i++) {

            const int lId =i;
            const int rId =i + 1;


            float leftChannel = (float)audioValues[lId] / 32767.0f;
            float rightChannel = (float)audioValues[rId] / 32767.0f;
             volP[i % volN] = leftChannel+ rightChannel;


            const float baseA = fmod((float)i,  fortyHZ          * 2.0f ) / (   fortyHZ           * 2.0f);
            const float baseB = fmod((float)i, (fortyHZ + 1.45f) * 2.0f ) / ( ( fortyHZ + 1.45f ) * 2.0f);
            const float baseC = fmod((float)i, (fortyHZ + 2.0f ) * 2.0f ) / ( ( fortyHZ + 2.0f  ) * 2.0f);

            float v = 0;

            // improve the prediction quality with a delay/lookahead 
            const int lookahead = MIN(volN, remainingLength);
            for(int j = 1; j < lookahead; j++) {
                 v += fabsf(fmaxf(volP[j], volP[j - 1]) - fminf(volP[j], volP[j -1]));    
            }

            v /= (float) lookahead * 2.0f;

            if(v >= 0.1f && atLeast <= 0) {
                atLeast = (int)minDuration;
                wprintf(L"Whomp\n"); // silly output
            } 

            // ugly but simple possibility to avaid overdrive
            float normalizedResultLeft = leftChannel * 0.5f;
            float normalizedResultRight = rightChannel * 0.5f;

            if(atLeast-- > 0) {
                float Whomp = sin(baseA * M_PI * 2) * 0.8 
                    + sin(baseB * M_PI * 2) * 0.2
                    + sin(baseC * M_PI * 2) * 0.01;

                 // (sin(x * pi * 2) + sin(x * pi * 4)) * 0.57
                 float x = (minDuration - (float)atLeast ) / minDuration;
                 float asdr = (sinf(x * M_PI * 2.0f) + sin(x * M_PI * 4.0f)) * 0.567;

                 normalizedResultLeft  += Whomp * 0.5 * asdr;
                 normalizedResultRight += Whomp * 0.5 * asdr;
            }

            // map the mormalized data back to pa values
            audioValues[lId] = (short) clampf(  normalizedResultLeft * 32767.0f,-32767,32767);
            audioValues[rId] = (short) clampf(  normalizedResultRight * 32767.0f,-32767,32767);

        }
    };

    bool playing = sad_playStream(mStream);

    sad_cleanupStream(mStream);

    if(sadInitOk)
        sad_exitPulseAudio();
}