libavresample/resample.c File Reference

#include "libavutil/libm.h"
#include "libavutil/log.h"
#include "internal.h"
#include "audio_data.h"

Go to the source code of this file.

Data Structures
struct	ResampleContext
Defines
#define	FILTER_SHIFT   15
#define	FELEM   int16_t
#define	FELEM2   int32_t
#define	FELEML   int64_t
#define	FELEM_MAX   INT16_MAX
#define	FELEM_MIN   INT16_MIN
#define	WINDOW_TYPE   9
Functions
static double	bessel (double x)
	0th order modified bessel function of the first kind.
static int	build_filter (FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type)
	Build a polyphase filterbank.
ResampleContext *	ff_audio_resample_init (AVAudioResampleContext *avr)
	Allocate and initialize a ResampleContext.
void	ff_audio_resample_free (ResampleContext **c)
	Free a ResampleContext.
int	avresample_set_compensation (AVAudioResampleContext *avr, int sample_delta, int compensation_distance)
	Set compensation for resampling.
static int	resample (ResampleContext *c, int16_t *dst, const int16_t *src, int *consumed, int src_size, int dst_size, int update_ctx)
int	ff_audio_resample (ResampleContext *c, AudioData *dst, AudioData *src, int *consumed)
	Resample audio data.
int	avresample_get_delay (AVAudioResampleContext *avr)
	Return the number of samples currently in the resampling delay buffer.

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Define Documentation

#define FELEM   int16_t

Definition at line 46 of file resample.c.

#define FELEM2   int32_t

Definition at line 47 of file resample.c.

#define FELEM_MAX   INT16_MAX

Definition at line 49 of file resample.c.

#define FELEM_MIN   INT16_MIN

Definition at line 50 of file resample.c.

#define FELEML   int64_t

Definition at line 48 of file resample.c.

#define FILTER_SHIFT   15

Definition at line 45 of file resample.c.

#define WINDOW_TYPE   9

Definition at line 51 of file resample.c.

---

Function Documentation

int avresample_get_delay

(

AVAudioResampleContext *

avr

)

Return the number of samples currently in the resampling delay buffer.

When resampling, there may be a delay between the input and output. Any unconverted samples in each call are stored internally in a delay buffer. This function allows the user to determine the current number of samples in the delay buffer, which can be useful for synchronization.

See also:

avresample_convert()

Parameters:

avr

audio resample context

Returns:

number of samples currently in the resampling delay buffer

Definition at line 474 of file resample.c.

Referenced by filter_samples(), get_delay(), main(), and request_frame().

int avresample_set_compensation	(	AVAudioResampleContext *	avr,
		int	sample_delta,
		int	compensation_distance
	)

Set compensation for resampling.

This can be called anytime after avresample_open(). If resampling was not being done previously, the AVAudioResampleContext is closed and reopened with resampling enabled. In this case, any samples remaining in the output FIFO and the current channel mixing matrix will be restored after reopening the context.

Parameters:

	avr	audio resample context
	sample_delta	compensation delta, in samples
	compensation_distance	compensation distance, in samples

Returns:

0 on success, negative AVERROR code on failure

Definition at line 240 of file resample.c.

Referenced by filter_samples().

static double bessel

(

double

x

)

[static]

0th order modified bessel function of the first kind.

Definition at line 74 of file resample.c.

static int build_filter	(	FELEM *	filter,
		double	factor,
		int	tap_count,
		int	phase_count,
		int	scale,
		int	type
	)			[static]

Build a polyphase filterbank.

Parameters:

[out]	filter	filter coefficients
	factor	resampling factor
	tap_count	tap count
	phase_count	phase count
	scale	wanted sum of coefficients for each filter
	type	0->cubic 1->blackman nuttall windowed sinc 2..16->kaiser windowed sinc beta=2..16

Returns:

0 on success, negative AVERROR code on failure

Definition at line 103 of file resample.c.

int ff_audio_resample	(	ResampleContext *	c,
		AudioData *	dst,
		AudioData *	src,
		int *	consumed
	)

Resample audio data.

Changes the sample rate.

All samples in the source data may not be consumed depending on the resampling parameters and the size of the output buffer. The unconsumed samples are automatically added to the start of the source in the next call. If the destination data can be reallocated, that may be done in this function in order to fit all available output. If it cannot be reallocated, fewer input samples will be consumed in order to have the output fit in the destination data buffers.

Parameters:

	c	ResampleContext
	dst	destination audio data
	src	source audio data
	consumed	number of samples consumed from the source

Returns:

number of samples written to the destination

Definition at line 419 of file resample.c.

Referenced by avresample_convert().

void ff_audio_resample_free

(

ResampleContext **

c

)

Free a ResampleContext.

Parameters:

c

ResampleContext

Definition at line 231 of file resample.c.

Referenced by avresample_close().

ResampleContext* ff_audio_resample_init

(

AVAudioResampleContext *

avr

)

Allocate and initialize a ResampleContext.

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

Parameters:

avr

AVAudioResampleContext

Returns:

newly-allocated ResampleContext

Definition at line 164 of file resample.c.

Referenced by avresample_open().

static int resample	(	ResampleContext *	c,
		int16_t *	dst,
		const int16_t *	src,
		int *	consumed,
		int	src_size,
		int	dst_size,
		int	update_ctx
	)			[static]

Definition at line 314 of file resample.c.

Referenced by avfilter_register_all(), ff_audio_resample(), and swr_convert_internal().