libavcodec/resample2.c File Reference

audio resampling More...

#include "avcodec.h"
#include "dsputil.h"

Go to the source code of this file.

Data Structures
struct	AVResampleContext
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.
void	av_build_filter (FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type)
	builds a polyphase filterbank.
AVResampleContext *	av_resample_init (int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff)
	Initializes an audio resampler.
void	av_resample_close (AVResampleContext *c)
void	av_resample_compensate (AVResampleContext *c, int sample_delta, int compensation_distance)
	Compensates samplerate/timestamp drift.
int	av_resample (AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx)
	resamples.

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Detailed Description

audio resampling

Author:

Michael Niedermayer <michaelni@gmx.at>

Definition in file resample2.c.

---

Define Documentation

#define FELEM   int16_t

Definition at line 34 of file resample2.c.

Referenced by av_resample(), and av_resample_init().

#define FELEM2   int32_t

Definition at line 35 of file resample2.c.

Referenced by av_resample().

#define FELEM_MAX   INT16_MAX

Definition at line 37 of file resample2.c.

Referenced by av_build_filter().

#define FELEM_MIN   INT16_MIN

Definition at line 38 of file resample2.c.

Referenced by av_build_filter().

#define FELEML   int64_t

Definition at line 36 of file resample2.c.

Referenced by av_resample().

#define FILTER_SHIFT   15

Definition at line 32 of file resample2.c.

Referenced by av_build_filter(), av_resample(), and av_resample_init().

#define WINDOW_TYPE   9

Definition at line 39 of file resample2.c.

Referenced by av_resample_init().

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Function Documentation

void av_build_filter	(	FELEM *	filter,
		double	factor,
		int	tap_count,
		int	phase_count,
		int	scale,
		int	type
	)

builds a polyphase filterbank.

Parameters:

	factor	resampling factor
	scale	wanted sum of coefficients for each filter
	type	0->cubic, 1->blackman nuttall windowed sinc, 2..16->kaiser windowed sinc beta=2..16

Definition at line 95 of file resample2.c.

int av_resample	(	struct AVResampleContext *	c,
		short *	dst,
		short *	src,
		int *	consumed,
		int	src_size,
		int	dst_size,
		int	update_ctx
	)

resamples.

Parameters:

	src	an array of unconsumed samples
	consumed	the number of samples of src which have been consumed are returned here
	src_size	the number of unconsumed samples available
	dst_size	the amount of space in samples available in dst
	update_ctx	If this is 0 then the context will not be modified, that way several channels can be resampled with the same context.

Returns:

the number of samples written in dst or -1 if an error occurred

Definition at line 213 of file resample2.c.

Referenced by audio_resample().

void av_resample_close

(

AVResampleContext *

c

)

Definition at line 202 of file resample2.c.

Referenced by audio_resample_close().

void av_resample_compensate	(	struct AVResampleContext *	c,
		int	sample_delta,
		int	compensation_distance
	)

Compensates samplerate/timestamp drift.

The compensation is done by changing the resampler parameters, so no audible clicks or similar distortions occur

Parameters:

	compensation_distance	distance in output samples over which the compensation should be performed
	sample_delta	number of output samples which should be output less

example: av_resample_compensate(c, 10, 500) here instead of 510 samples only 500 samples would be output

note, due to rounding the actual compensation might be slightly different, especially if the compensation_distance is large and the in_rate used during init is small

Definition at line 207 of file resample2.c.

Referenced by av_resample(), and do_audio_out().

AVResampleContext* av_resample_init	(	int	out_rate,
		int	in_rate,
		int	filter_length,
		int	log2_phase_count,
		int	linear,
		double	cutoff
	)			[read]

Initializes an audio resampler.

Note, if either rate is not an integer then simply scale both rates up so they are.

Parameters:

	filter_length	length of each FIR filter in the filterbank relative to the cutoff freq
	log2_phase_count	log2 of the number of entries in the polyphase filterbank
	linear	If 1 then the used FIR filter will be linearly interpolated between the 2 closest, if 0 the closest will be used
	cutoff	cutoff frequency, 1.0 corresponds to half the output sampling rate

Definition at line 178 of file resample2.c.

Referenced by av_audio_resample_init().

static double bessel

(

double

x

)

[static]

0th order modified bessel function of the first kind.

Definition at line 76 of file resample2.c.

Referenced by av_build_filter(), and ff_kbd_window_init().