PortAudio real-time audio processing for continuous input stream

Question

I am using PortAudio to implement a real-time audio processing.

My primary task is to acquire data from mic continuously and provide 100 samples for processing

Answer 1

Example code of processing audio input:

#define FRAME_SIZE                 1024
#define CIRCULAR_BUFFER_SIZE       (FRAME_SIZE * 4)

float buffer[CIRCULAR_BUFFER_SIZE];

typedef struct {
     int read, write;
     float vol;
} paData;

static int paStreamCallback(const void* input, void* output,
                            unsigned long samplesPerFrame,
                            const PaStreamCallbackTimeInfo* timeInfo,
                            PaStreamCallbackFlags statusFlags,
                            void* userData) {

    paData *data = (paData *)userData;
    // Write input buffer to our buffer: (memcpy function is fine, just a for loop of writing data
    memcpy(&buffer[write], input, samplesPerFrame); // Assuming samplesPerFrame = FRAME_SIZE

    // Increment write/wraparound
    write = (write + FRAME_SIZE) % CIRCULAR_BUFFER_SIZE;

    // dummy algorithm for processing blocks:
    processAlgorithm(&buffer[read]);

    // Write output
    float *dummy_buffer = &buffer[read]; // just for easy increment
    for (int i = 0; i < samplesPerFrame; i++) {
         // Mix audio input and processed input; 50% mix
         output[i] = input[i] * 0.5 + dummy_buffer[i] * 0.5;
    }

    // Increment read/wraparound
    read = (read + FRAME_SIZE) % CIRCULAR_BUFFER_SIZE;

    return paContinue;
}

int main(void) {
     // Initialize code here; any memory allocation needs to be done here! default buffers to 0 (silence)
     // initialize paData too; write = 0, read = 3072
     // read is 3072 because I'm thinking about this like a delay system.
}

Take this with a grain of salt; Obviously better ways of doing this but it can be used as a starting point.