Mixing 16 bit linear PCM streams and avoiding clipping/overflow

Question

I\'ve trying to mix together 2 16bit linear PCM audio streams and I can\'t seem to overcome the noise issues. I think they are coming from overflow when mixing samples together.

Answer 1

here's a descriptive implementation:

short int mix_sample(short int sample1, short int sample2) {
    const int32_t result(static_cast(sample1) + static_cast(sample2));
    typedef std::numeric_limits Range;
    if (Range::max() < result)
        return Range::max();
    else if (Range::min() > result)
        return Range::min();
    else
        return result;
}

to mix, it's just add and clip!

to avoid clipping artifacts, you will want to use saturation or a limiter. ideally, you will have a small int32_t buffer with a small amount of lookahead. this will introduce latency.

more common than limiting everywhere, is to leave a few bits' worth of 'headroom' in your signal.