dsp.h File Reference

Sound processing chain, float32 inside, Q31 in and out: ReplayGain -> preamp -> parametric EQ (<=10 bands, RBJ biquads, AutoEQ import) -> crossfeed (Bauer-style, bs2b-like) -> software volume -> limiter -> dither. More...

#include "audio_player/audio.h"

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Data Structures
struct	peq_band_t
struct	eq_preset_t
struct	dsp_config_t
struct	biquad_coef_t
	Low-level building blocks, exported for tests and for the Bluetooth path. More...

Macros
#define	DSP_MAX_BANDS   10
#define	DSP_PRESET_NAME_MAX   48
#define	DSP_DRAIN_MAX   128u
	Most frames dsp_process_out() adds to a chunk: the limiter delay line (about 1 ms).

Typedefs
typedef struct dsp	dsp_t

Enumerations
enum	peq_type_t {   PEQ_PEAK = 0 , PEQ_LOW_SHELF , PEQ_HIGH_SHELF , PEQ_LOW_PASS ,   PEQ_HIGH_PASS }
enum	rg_mode_t { RG_OFF = 0 , RG_TRACK , RG_ALBUM , RG_AUTO }
enum	{   DSP_FLAG_RG = 1u << 0 , DSP_FLAG_EQ = 1u << 1 , DSP_FLAG_CROSSFEED = 1u << 2 , DSP_FLAG_SW_VOLUME = 1u << 3 ,   DSP_FLAG_LIMITER = 1u << 4 , DSP_FLAG_DITHER = 1u << 5 , DSP_FLAG_RESAMPLE = 1u << 6 }
	Active processing flags (for a "signal path" display). More...

Functions
int	eq_preset_parse_autoeq (const char *text, eq_preset_t *out)
	Parse AutoEQ "ParametricEQ.txt" (lines like "Preamp: -6.3 dB" and "Filter 1: ON PK Fc 105 Hz Gain -2.9 dB Q 0.70", types PK, LSC, HSC, LS, HS, LP, HP).
int	eq_preset_format_autoeq (const eq_preset_t *p, char *out, size_t out_size)
	Write the same text format (so presets round-trip). Returns bytes written or <0.
uint32_t	eq_builtin_count (void)
	Built-in presets: "Flat", "Bass", "Treble", "Vocal", "Loudness". Index 0 is Flat.
const eq_preset_t *	eq_builtin_get (uint32_t index)
void	dsp_config_defaults (dsp_config_t *c)
dsp_t *	dsp_create (void)
void	dsp_destroy (dsp_t *d)
void	dsp_configure (dsp_t *d, const dsp_config_t *cfg, uint32_t sample_rate, uint8_t channels)
	(Re)configure for a format. Keeps filter state when only gains change.
void	dsp_set_replaygain (dsp_t *d, float track_gain_db, float track_peak, float album_gain_db, float album_peak, bool album_context)
	ReplayGain values of the current track (NAN when absent). Call on track change.
void	dsp_process (dsp_t *d, int32_t *pcm, uint32_t frames)
	in place
uint32_t	dsp_process_out (dsp_t *d, int32_t *pcm, uint32_t frames, uint32_t cap_frames)
	dsp_process() with room for more output.
void	dsp_reset (dsp_t *d)
	clear filter state (seek, track change)
bool	dsp_is_bypass (const dsp_t *d)
uint32_t	dsp_active_flags (const dsp_t *d)
void	biquad_design (biquad_coef_t *c, peq_type_t type, float fs, float f0, float gain_db, float q)
	RBJ Audio EQ Cookbook designs.
float	biquad_response_db (const biquad_coef_t *c, float fs, float f)
	Magnitude response in dB at frequency f (for EQ curve drawing and tests).
void	pcm_q31_to_f32 (const int32_t *in, float *out, size_t samples)
	Q31 <-> float.
void	pcm_f32_to_q31 (const float *in, int32_t *out, size_t samples)
	saturating
void	pcm_q31_to_s16_dither (const int32_t *in, int16_t *out, size_t samples, uint32_t *state)
	Reduce to 16 bits with TPDF dither (state = LCG seed, keep per stream).
void	pcm_mono_to_stereo (const int32_t *in, int32_t *out, size_t frames)
	Upmix mono Q31 to stereo. in == out is allowed (the buffer must hold 2*frames samples).
float	db_to_lin (float db)
float	lin_to_db (float lin)

Detailed Description

Sound processing chain, float32 inside, Q31 in and out: ReplayGain -> preamp -> parametric EQ (<=10 bands, RBJ biquads, AutoEQ import) -> crossfeed (Bauer-style, bs2b-like) -> software volume -> limiter -> dither.

When every stage is off and volume is unity, dsp_process() leaves samples untouched (bit-perfect path) and dsp_is_bypass() returns true.

Macro Definition Documentation

DSP_DRAIN_MAX

#define DSP_DRAIN_MAX   128u

Most frames dsp_process_out() adds to a chunk: the limiter delay line (about 1 ms).

DSP_MAX_BANDS

#define DSP_MAX_BANDS   10

DSP_PRESET_NAME_MAX

#define DSP_PRESET_NAME_MAX   48

Typedef Documentation

dsp_t

typedef struct dsp dsp_t

Enumeration Type Documentation

anonymous enum

anonymous enum

Active processing flags (for a "signal path" display).

Enumerator
DSP_FLAG_RG
DSP_FLAG_EQ
DSP_FLAG_CROSSFEED
DSP_FLAG_SW_VOLUME
DSP_FLAG_LIMITER
DSP_FLAG_DITHER
DSP_FLAG_RESAMPLE	set by the player, not by dsp

peq_type_t

enum peq_type_t

Enumerator
PEQ_PEAK
PEQ_LOW_SHELF
PEQ_HIGH_SHELF
PEQ_LOW_PASS
PEQ_HIGH_PASS

rg_mode_t

enum rg_mode_t

Enumerator
RG_OFF
RG_TRACK
RG_ALBUM
RG_AUTO

Function Documentation

biquad_design()

void biquad_design	(	biquad_coef_t *	c,
		peq_type_t	type,
		float	fs,
		float	f0,
		float	gain_db,
		float	q
	)

RBJ Audio EQ Cookbook designs.

biquad_response_db()

float biquad_response_db	(	const biquad_coef_t *	c,
		float	fs,
		float	f
	)

Magnitude response in dB at frequency f (for EQ curve drawing and tests).

db_to_lin()

float db_to_lin

(

float

db

)

dsp_active_flags()

uint32_t dsp_active_flags

(

const dsp_t *

d

)

dsp_config_defaults()

void dsp_config_defaults

(

dsp_config_t *

c

)

dsp_configure()

void dsp_configure	(	dsp_t *	d,
		const dsp_config_t *	cfg,
		uint32_t	sample_rate,
		uint8_t	channels
	)

(Re)configure for a format. Keeps filter state when only gains change.

dsp_create()

dsp_t * dsp_create

(

void

)

dsp_destroy()

void dsp_destroy

(

dsp_t *

d

)

dsp_is_bypass()

bool dsp_is_bypass

(

const dsp_t *

d

)

dsp_process()

void dsp_process	(	dsp_t *	d,
		int32_t *	pcm,
		uint32_t	frames
	)

in place

dsp_process_out()

uint32_t dsp_process_out	(	dsp_t *	d,
		int32_t *	pcm,
		uint32_t	frames,
		uint32_t	cap_frames
	)

dsp_process() with room for more output.

While active the chain delays the audio by the limiter lookahead. When it goes to bypass (a gain ramp ended at unity, or dsp_configure() switched every stage off), that delayed audio is played out instead of dropped: after the chunk when the switch happened inside this call, before it when it happened earlier. Later chunks pass bit-exact. pcm holds frames frames and has room for cap_frames; returns the frames now in pcm. frames may be 0 (only the delayed audio, e.g. at the end of the stream). Without room for DSP_DRAIN_MAX more frames the delayed audio is dropped, as dsp_process() does.

dsp_reset()

void dsp_reset

(

dsp_t *

d

)

clear filter state (seek, track change)

dsp_set_replaygain()

void dsp_set_replaygain	(	dsp_t *	d,
		float	track_gain_db,
		float	track_peak,
		float	album_gain_db,
		float	album_peak,
		bool	album_context
	)

ReplayGain values of the current track (NAN when absent). Call on track change.

eq_builtin_count()

uint32_t eq_builtin_count

(

void

)

Built-in presets: "Flat", "Bass", "Treble", "Vocal", "Loudness". Index 0 is Flat.

eq_builtin_get()

const eq_preset_t * eq_builtin_get

(

uint32_t

index

)

eq_preset_format_autoeq()

int eq_preset_format_autoeq	(	const eq_preset_t *	p,
		char *	out,
		size_t	out_size
	)

Write the same text format (so presets round-trip). Returns bytes written or <0.

eq_preset_parse_autoeq()

int eq_preset_parse_autoeq	(	const char *	text,
		eq_preset_t *	out
	)

Parse AutoEQ "ParametricEQ.txt" (lines like "Preamp: -6.3 dB" and "Filter 1: ON PK Fc 105 Hz Gain -2.9 dB Q 0.70", types PK, LSC, HSC, LS, HS, LP, HP).

Returns CORE_OK or CORE_ECORRUPT. Extra bands beyond DSP_MAX_BANDS are dropped with a warning.

lin_to_db()

float lin_to_db

(

float

lin

)

pcm_f32_to_q31()

void pcm_f32_to_q31	(	const float *	in,
		int32_t *	out,
		size_t	samples
	)

saturating

pcm_mono_to_stereo()

void pcm_mono_to_stereo	(	const int32_t *	in,
		int32_t *	out,
		size_t	frames
	)

Upmix mono Q31 to stereo. in == out is allowed (the buffer must hold 2*frames samples).

pcm_q31_to_f32()

void pcm_q31_to_f32	(	const int32_t *	in,
		float *	out,
		size_t	samples
	)

Q31 <-> float.

pcm_q31_to_s16_dither()

void pcm_q31_to_s16_dither	(	const int32_t *	in,
		int16_t *	out,
		size_t	samples,
		uint32_t *	state
	)

Reduce to 16 bits with TPDF dither (state = LCG seed, keep per stream).