dither.c File Reference

Dithered Audio Sample Quantization. More...

#include <math.h>
#include <stdint.h>
#include "libavutil/attributes.h"
#include "libavutil/common.h"
#include "libavutil/lfg.h"
#include "libavutil/mem.h"
#include "libavutil/samplefmt.h"
#include "audio_convert.h"
#include "dither.h"
#include "internal.h"

Go to the source code of this file.

Data Structures
struct	DitherState
struct	DitherContext

Macros
#define	MUTE_THRESHOLD_SEC   0.000333
#define	S16_SCALE   32753.0f
#define	LFG_SCALE   (1.0f / (2.0f * INT32_MAX))
#define	SQRT_1_6   0.40824829046386301723f

Functions
static void	dither_int_to_float_rectangular_c (float *dst, int *src, int len)
static void	dither_int_to_float_triangular_c (float *dst, int *src0, int len)
static void	quantize_c (int16_t *dst, const float *src, float *dither, int len)
static void	dither_highpass_filter (float *src, int len)
static int	generate_dither_noise (DitherContext *c, DitherState *state, int min_samples)
static void	quantize_triangular_ns (DitherContext *c, DitherState *state, int16_t *dst, const float *src, int nb_samples)
static int	convert_samples (DitherContext *c, int16_t **dst, float *const *src, int channels, int nb_samples)
int	ff_convert_dither (DitherContext *c, AudioData *dst, AudioData *src)
	Convert audio sample format with dithering.
void	ff_dither_free (DitherContext **cp)
	Free a DitherContext.
static av_cold void	dither_init (DitherDSPContext *ddsp, enum AVResampleDitherMethod method)
DitherContext *	ff_dither_alloc (AVAudioResampleContext *avr, enum AVSampleFormat out_fmt, enum AVSampleFormat in_fmt, int channels, int sample_rate, int apply_map)
	Allocate and initialize a DitherContext.

Variables
static const float	ns_48_coef_b [4]
static const float	ns_48_coef_a [4]
static const float	ns_44_coef_b [4]
static const float	ns_44_coef_a [4]

Detailed Description

Dithered Audio Sample Quantization.

Converts from dbl, flt, or s32 to s16 using dithering.

Definition in file dither.c.

Macro Definition Documentation

#define MUTE_THRESHOLD_SEC   0.000333

Definition at line 78 of file dither.c.

Referenced by ff_dither_alloc().

#define S16_SCALE   32753.0f

Definition at line 82 of file dither.c.

Referenced by quantize_c(), and quantize_triangular_ns().

#define LFG_SCALE   (1.0f / (2.0f * INT32_MAX))

Definition at line 85 of file dither.c.

Referenced by dither_int_to_float_rectangular_c(), and dither_int_to_float_triangular_c().

#define SQRT_1_6   0.40824829046386301723f

Definition at line 131 of file dither.c.

Referenced by dither_highpass_filter().

Function Documentation

static void dither_int_to_float_rectangular_c ( float *  dst, int *  src, int  len  )

static

Definition at line 105 of file dither.c.

Referenced by dither_init().

static void dither_int_to_float_triangular_c ( float *  dst, int *  src0, int  len  )

static

Definition at line 112 of file dither.c.

Referenced by dither_init().

static void quantize_c ( int16_t *  dst, const float *  src, float *  dither, int  len  )

static

Definition at line 124 of file dither.c.

Referenced by dither_init(), and ff_convert_dither().

static void dither_highpass_filter ( float *  src, int  len  )

static

Definition at line 133 of file dither.c.

Referenced by generate_dither_noise().

static int generate_dither_noise ( DitherContext *  c, DitherState *  state, int  min_samples  )

static

Definition at line 142 of file dither.c.

Referenced by convert_samples(), and ff_dither_alloc().

static void quantize_triangular_ns ( DitherContext *  c, DitherState *  state, int16_t *  dst, const float *  src, int  nb_samples  )

static

Definition at line 172 of file dither.c.

Referenced by convert_samples().

static int convert_samples ( DitherContext *  c, int16_t **  dst, float *const *  src, int  channels, int  nb_samples  )

static

Definition at line 211 of file dither.c.

Referenced by ff_convert_dither().

int ff_convert_dither	(	DitherContext *	c,
		AudioData *	dst,
		AudioData *	src
	)

Convert audio sample format with dithering.

Parameters

c	DitherContext
dst	destination audio data
src	source audio data

Returns

0 if ok, negative AVERROR code on failure

Definition at line 242 of file dither.c.

void ff_dither_free

(

DitherContext **

c

)

Free a DitherContext.

Parameters

c	DitherContext

Definition at line 312 of file dither.c.

Referenced by ff_dither_alloc().

static av_cold void dither_init ( DitherDSPContext *  ddsp, enum AVResampleDitherMethod  method  )

static

Definition at line 329 of file dither.c.

Referenced by ff_dither_alloc().

DitherContext* ff_dither_alloc	(	AVAudioResampleContext *	avr,
		enum AVSampleFormat	out_fmt,
		enum AVSampleFormat	in_fmt,
		int	channels,
		int	sample_rate,
		int	apply_map
	)

Allocate and initialize a DitherContext.

The parameters in the AVAudioResampleContext are used to initialize the DitherContext.

Parameters

avr	AVAudioResampleContext

Returns

newly-allocated DitherContext

Definition at line 345 of file dither.c.

Variable Documentation

const float ns_48_coef_b[4]

static

Initial value:

= {
    2.2374f, -0.7339f, -0.1251f, -0.6033f
}

Definition at line 89 of file dither.c.

Referenced by ff_dither_alloc().

const float ns_48_coef_a[4]

static

Initial value:

= {
    0.9030f, 0.0116f, -0.5853f, -0.2571f
}

Definition at line 93 of file dither.c.

Referenced by ff_dither_alloc().

const float ns_44_coef_b[4]

static

Initial value:

= {
    2.2061f, -0.4707f, -0.2534f, -0.6213f
}

Definition at line 97 of file dither.c.

Referenced by ff_dither_alloc().

const float ns_44_coef_a[4]

static

Initial value:

= {
    1.0587f, 0.0676f, -0.6054f, -0.2738f
}

Definition at line 101 of file dither.c.

Referenced by ff_dither_alloc().