for (int i = 0; i < in->frames(); ++i) {
float const left = in->data()[0][i];
float const right = in->data()[1][i];
float const mid = (left + right) / 2;
for (int i = 0; i < in->frames(); ++i) {
float const left = in->data()[0][i];
float const right = in->data()[1][i];
float const mid = (left + right) / 2;