Ls = sf_open ("build/test/upmixer_a_test/Ls.wav", SFM_WRITE, &info);
Rs = sf_open ("build/test/upmixer_a_test/Rs.wav", SFM_WRITE, &info);
Ls = sf_open ("build/test/upmixer_a_test/Ls.wav", SFM_WRITE, &info);
Rs = sf_open ("build/test/upmixer_a_test/Rs.wav", SFM_WRITE, &info);