resample2.c File Reference

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Detailed Description

audio resampling

Author:

Michael Niedermayer <michaelni@gmx.at>

Definition in file resample2.c.

Go to the source code of this file.

Classes
struct	AVResampleContext
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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Function Documentation

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 ac3_window_init(), and av_build_filter().

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.

AVResampleContext* av_resample_init	(	int	out_rate,
		int	in_rate,
		int	filter_size,
		int	phase_shift,
		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.

Definition at line 182 of file resample2.c.

Referenced by audio_resample_init().

void av_resample_close

(

AVResampleContext *

c

)

Definition at line 204 of file resample2.c.

Referenced by audio_resample_close().

void av_resample_compensate	(	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 ocur

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 221 of file resample2.c.

Referenced by av_resample().

int av_resample	(	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 wont 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 occured

Definition at line 236 of file resample2.c.

Referenced by audio_resample().