freq_magnitude
carrier = freq_magnitude(x, N, carrier_freq);
stereo = freq_magnitude(x, N, stereo_freq);
dual = freq_magnitude(x, N, dual_freq);
s32 sap_ref = freq_magnitude(x, N, FREQ_BTSC_SAP_REF);
s32 sap = freq_magnitude(x, N, FREQ_BTSC_SAP);
s32 dual_ref = freq_magnitude(x, N, FREQ_BTSC_DUAL_REF);
s32 dual = freq_magnitude(x, N, FREQ_BTSC_DUAL);