One biquad section's normalised coefficients [b0, b1, b2, a1, a2] (a0 folded to 1). The
recurrence the engine runs is y = b0·x + b1·x₁ + b2·x₂ − a1·y₁ − a2·y₂, so the two a
terms are the (positive) denominator coefficients the DSP SUBTRACTS. This is "the engine's
biquad": the native mixer (mixer.c omx_biquad) consumes exactly this 5-tuple.
One biquad section's normalised coefficients
[b0, b1, b2, a1, a2](a0 folded to 1). The recurrence the engine runs isy = b0·x + b1·x₁ + b2·x₂ − a1·y₁ − a2·y₂, so the twoaterms are the (positive) denominator coefficients the DSP SUBTRACTS. This is "the engine's biquad": the native mixer (mixer.comx_biquad) consumes exactly this 5-tuple.