EQ - how to add it?

[METhOphetamine]

Equalization was one of the potential features advertised when the Buds got announced. Unfortunately it's not even on this repo's roadmap. Which I think is a shame because many people would be interested in it (part of the audiophile "community" that does not believe in pixies inside headphones). The frequency response is also Raycon level bad so EQ is kinda required to make it sound ok.

There are functions to generate coefficients for FIR and IIR filtering. Also HW IRR EQ is mentioned in the audio_process.c file. But I don't know how to actually implement it.

[FintasticMan]

The current EQ values are specified in

OpenPineBuds/config/open_source/tgt_hardware.c

Lines 999 to 1017 in 4a97664

	const IIR_CFG_T audio_eq_sw_iir_cfg = {.gain0 = 0,
	.gain1 = 0,
	.num = 14,
	.param = {
	{IIR_TYPE_PEAK, -2.18, 10, 2},
	{IIR_TYPE_PEAK, 7.27, 21, 2},
	{IIR_TYPE_PEAK, 2.13, 42, 2},
	{IIR_TYPE_PEAK, -1.53, 83, 2},
	{IIR_TYPE_PEAK, -0.9, 120, 2},
	{IIR_TYPE_PEAK, -4.23, 166, 2},
	{IIR_TYPE_PEAK, -1.08, 333, 2},
	{IIR_TYPE_PEAK, -1.37, 577, 2},
	{IIR_TYPE_PEAK, 0.8, 1000, 2},
	{IIR_TYPE_PEAK, 5.35, 2000, 2},
	{IIR_TYPE_PEAK, 3.2, 4000, 2},
	{IIR_TYPE_PEAK, -4.96, 8000, 2},
	{IIR_TYPE_PEAK, 13.58, 16000, 2},
	{IIR_TYPE_PEAK, 8.89, 20000, 2},
	}};