libavfilter/af_atempo.c File Reference

tempo scaling audio filter -- an implementation of WSOLA algorithm More...

#include <float.h>
#include "libavcodec/avfft.h"
#include "libavutil/audioconvert.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/eval.h"
#include "libavutil/opt.h"
#include "libavutil/samplefmt.h"
#include "avfilter.h"
#include "audio.h"
#include "internal.h"

Go to the source code of this file.

Data Structures

struct AudioFragment

A fragment of audio waveform. More...

struct ATempoContext

Filter state machine. More...

Defines

#define RE_MALLOC_OR_FAIL(field, field_size)

#define yae_init_xdat(scalar_type, scalar_max)

A helper macro for initializing complex data buffer with scalar data of a given type.

#define yae_blend(scalar_type)

A helper macro for blending the overlap region of previous and current audio fragment.

Enumerations

enum FilterState {
YAE_LOAD_FRAGMENT, YAE_ADJUST_POSITION, YAE_RELOAD_FRAGMENT, YAE_OUTPUT_OVERLAP_ADD,
YAE_FLUSH_OUTPUT
}

Filter state machine states. More...

Functions

static void yae_clear (ATempoContext *atempo)

Reset filter to initial state, do not deallocate existing local buffers.

static void yae_release_buffers (ATempoContext *atempo)

Reset filter to initial state and deallocate all buffers.

static int yae_reset (ATempoContext *atempo, enum AVSampleFormat format, int sample_rate, int channels)

Prepare filter for processing audio data of given format, sample rate and number of channels.

static int yae_set_tempo (AVFilterContext *ctx, const char *arg_tempo)

static AudioFragment * yae_curr_frag (ATempoContext *atempo)

static AudioFragment * yae_prev_frag (ATempoContext *atempo)

static void yae_downmix (ATempoContext *atempo, AudioFragment *frag)

Initialize complex data buffer of a given audio fragment with down-mixed mono data of appropriate scalar type.

static int yae_load_data (ATempoContext *atempo, const uint8_t **src_ref, const uint8_t *src_end, int64_t stop_here)

Populate the internal data buffer on as-needed basis.

static int yae_load_frag (ATempoContext *atempo, const uint8_t **src_ref, const uint8_t *src_end)

Populate current audio fragment data buffer.

static void yae_advance_to_next_frag (ATempoContext *atempo)

Prepare for loading next audio fragment.

static void yae_xcorr_via_rdft (FFTSample *xcorr, RDFTContext *complex_to_real, const FFTComplex *xa, const FFTComplex *xb, const int window)

Calculate cross-correlation via rDFT.

static int yae_align (AudioFragment *frag, const AudioFragment *prev, const int window, const int delta_max, const int drift, FFTSample *correlation, RDFTContext *complex_to_real)

Calculate alignment offset for given fragment relative to the previous fragment.

static int yae_adjust_position (ATempoContext *atempo)

Adjust current fragment position for better alignment with previous fragment.

static int yae_overlap_add (ATempoContext *atempo, uint8_t **dst_ref, uint8_t *dst_end)

Blend the overlap region of previous and current audio fragment and output the results to the given destination buffer.

static void yae_apply (ATempoContext *atempo, const uint8_t **src_ref, const uint8_t *src_end, uint8_t **dst_ref, uint8_t *dst_end)

Feed as much data to the filter as it is able to consume and receive as much processed data in the destination buffer as it is able to produce or store.

static int yae_flush (ATempoContext *atempo, uint8_t **dst_ref, uint8_t *dst_end)

Flush any buffered data from the filter.

static av_cold int init (AVFilterContext *ctx, const char *args)

static av_cold void uninit (AVFilterContext *ctx)

static int query_formats (AVFilterContext *ctx)

static int config_props (AVFilterLink *inlink)

static void push_samples (ATempoContext *atempo, AVFilterLink *outlink, int n_out)

static int filter_samples (AVFilterLink *inlink, AVFilterBufferRef *src_buffer)

static int request_frame (AVFilterLink *outlink)

static int process_command (AVFilterContext *ctx, const char *cmd, const char *arg, char *res, int res_len, int flags)

Variables

AVFilter avfilter_af_atempo

Detailed Description

tempo scaling audio filter -- an implementation of WSOLA algorithm

Based on MIT licensed yaeAudioTempoFilter.h and yaeAudioFragment.h from Apprentice Video player by Pavel Koshevoy. https://sourceforge.net/projects/apprenticevideo/

An explanation of SOLA algorithm is available at http://www.surina.net/article/time-and-pitch-scaling.html

WSOLA is very similar to SOLA, only one major difference exists between these algorithms. SOLA shifts audio fragments along the output stream, where as WSOLA shifts audio fragments along the input stream.

The advantage of WSOLA algorithm is that the overlap region size is always the same, therefore the blending function is constant and can be precomputed.

Definition in file af_atempo.c.

Define Documentation

#define RE_MALLOC_OR_FAIL	(	field,
		field_size		)

Value:

do {                                                        \
        av_freep(&field);                                       \
        field = av_malloc(field_size);                          \
        if (!field) {                                           \
            yae_release_buffers(atempo);                        \
            return AVERROR(ENOMEM);                             \
        }                                                       \
    } while (0)

Definition at line 214 of file af_atempo.c.

Referenced by yae_reset().

#define yae_blend ( scalar_type )

Value:

do {                                                                \
        const scalar_type *aaa = (const scalar_type *)a;                \
        const scalar_type *bbb = (const scalar_type *)b;                \
                                                                        \
        scalar_type *out     = (scalar_type *)dst;                      \
        scalar_type *out_end = (scalar_type *)dst_end;                  \
        int64_t i;                                                      \
                                                                        \
        for (i = 0; i < overlap && out < out_end;                       \
             i++, atempo->position[1]++, wa++, wb++) {                  \
            float w0 = *wa;                                             \
            float w1 = *wb;                                             \
            int j;                                                      \
                                                                        \
            for (j = 0; j < atempo->channels;                           \
                 j++, aaa++, bbb++, out++) {                            \
                float t0 = (float)*aaa;                                 \
                float t1 = (float)*bbb;                                 \
                                                                        \
                *out =                                                  \
                    frag->position[0] + i < 0 ?                         \
                    *aaa :                                              \
                    (scalar_type)(t0 * w0 + t1 * w1);                   \
            }                                                           \
        }                                                               \
        dst = (uint8_t *)out;                                           \
    } while (0)

A helper macro for blending the overlap region of previous and current audio fragment.

Definition at line 708 of file af_atempo.c.

Referenced by yae_overlap_add().

#define yae_init_xdat	(	scalar_type,
		scalar_max		)

A helper macro for initializing complex data buffer with scalar data of a given type.

Definition at line 333 of file af_atempo.c.

Referenced by yae_downmix().

Enumeration Type Documentation

enum FilterState

Filter state machine states.

Enumerator:

YAE_LOAD_FRAGMENT
YAE_ADJUST_POSITION
YAE_RELOAD_FRAGMENT
YAE_OUTPUT_OVERLAP_ADD
YAE_FLUSH_OUTPUT

Definition at line 76 of file af_atempo.c.

Function Documentation

static int config_props ( AVFilterLink * inlink ) [static]

Definition at line 1011 of file af_atempo.c.

static int filter_samples	(	AVFilterLink *	inlink,
		AVFilterBufferRef *	src_buffer
	)			`[static]`

Definition at line 1044 of file af_atempo.c.

static av_cold int init	(	AVFilterContext *	ctx,
		const char *	args
	)			`[static]`

Definition at line 952 of file af_atempo.c.

static int process_command	(	AVFilterContext *	ctx,
		const char *	cmd,
		const char *	arg,
		char *	res,
		int	res_len,
		int	flags
	)			`[static]`

Definition at line 1129 of file af_atempo.c.

static void push_samples	(	ATempoContext *	atempo,
		AVFilterLink *	outlink,
		int	n_out
	)			`[static]`

Definition at line 1023 of file af_atempo.c.

static int query_formats ( AVFilterContext * ctx ) [static]

Definition at line 970 of file af_atempo.c.

static int request_frame ( AVFilterLink * outlink ) [static]

Definition at line 1081 of file af_atempo.c.

static av_cold void uninit ( AVFilterContext * ctx ) [static]

Definition at line 964 of file af_atempo.c.

static int yae_adjust_position ( ATempoContext * atempo ) [static]

Adjust current fragment position for better alignment with previous fragment.

Returns:: alignment correction.

Definition at line 676 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

static void yae_advance_to_next_frag ( ATempoContext * atempo ) [static]

Prepare for loading next audio fragment.

Definition at line 566 of file af_atempo.c.

Referenced by yae_apply().

static int yae_align	(	AudioFragment *	frag,
		const AudioFragment *	prev,
		const int	window,
		const int	delta_max,
		const int	drift,
		FFTSample *	correlation,
		RDFTContext *	complex_to_real
	)			`[static]`

Calculate alignment offset for given fragment relative to the previous fragment.

Returns:: alignment offset of current fragment relative to previous.

Definition at line 622 of file af_atempo.c.

Referenced by yae_adjust_position().

static void yae_apply	(	ATempoContext *	atempo,
		const uint8_t **	src_ref,
		const uint8_t *	src_end,
		uint8_t **	dst_ref,
		uint8_t *	dst_end
	)			`[static]`

Feed as much data to the filter as it is able to consume and receive as much processed data in the destination buffer as it is able to produce or store.

Definition at line 800 of file af_atempo.c.

Referenced by filter_samples().

static void yae_clear ( ATempoContext * atempo ) [static]

Reset filter to initial state, do not deallocate existing local buffers.

Definition at line 153 of file af_atempo.c.

Referenced by yae_release_buffers(), and yae_reset().

static AudioFragment* yae_curr_frag ( ATempoContext * atempo ) [inline, static]

Definition at line 319 of file af_atempo.c.

Referenced by yae_adjust_position(), yae_advance_to_next_frag(), yae_apply(), yae_flush(), yae_load_frag(), and yae_overlap_add().

static void yae_downmix	(	ATempoContext *	atempo,
		AudioFragment *	frag
	)			`[static]`

Initialize complex data buffer of a given audio fragment with down-mixed mono data of appropriate scalar type.

Definition at line 383 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

static int yae_flush	(	ATempoContext *	atempo,
		uint8_t **	dst_ref,
		uint8_t *	dst_end
	)			`[static]`

Flush any buffered data from the filter.

Returns:: 0 if all data was completely stored in the dst buffer, AVERROR(EAGAIN) if more destination buffer space is required.

Definition at line 874 of file af_atempo.c.

Referenced by request_frame().

static int yae_load_data	(	ATempoContext *	atempo,
		const uint8_t **	src_ref,
		const uint8_t *	src_end,
		int64_t	stop_here
	)			`[static]`

Populate the internal data buffer on as-needed basis.

Returns:: 0 if requested data was already available or was successfully loaded, AVERROR(EAGAIN) if more input data is required.

Definition at line 411 of file af_atempo.c.

Referenced by yae_load_frag().

static int yae_load_frag	(	ATempoContext *	atempo,
		const uint8_t **	src_ref,
		const uint8_t *	src_end
	)			`[static]`

Populate current audio fragment data buffer.

Returns:: 0 when the fragment is ready, AVERROR(EAGAIN) if more input data is required.

Definition at line 486 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

static int yae_overlap_add	(	ATempoContext *	atempo,
		uint8_t **	dst_ref,
		uint8_t *	dst_end
	)			`[static]`

Blend the overlap region of previous and current audio fragment and output the results to the given destination buffer.

Returns:: 0 if the overlap region was completely stored in the dst buffer, AVERROR(EAGAIN) if more destination buffer space is required.

Definition at line 745 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

static AudioFragment* yae_prev_frag ( ATempoContext * atempo ) [inline, static]

Definition at line 324 of file af_atempo.c.

Referenced by yae_adjust_position(), yae_advance_to_next_frag(), and yae_overlap_add().

static void yae_release_buffers ( ATempoContext * atempo ) [static]

Reset filter to initial state and deallocate all buffers.

Definition at line 192 of file af_atempo.c.

Referenced by uninit(), and yae_reset().

static int yae_reset	(	ATempoContext *	atempo,
		enum AVSampleFormat	format,
		int	sample_rate,
		int	channels
	)			`[static]`

Prepare filter for processing audio data of given format, sample rate and number of channels.

Definition at line 228 of file af_atempo.c.

Referenced by config_props().

static int yae_set_tempo	(	AVFilterContext *	ctx,
		const char *	arg_tempo
	)			`[static]`

Definition at line 298 of file af_atempo.c.

Referenced by init(), and process_command().

static void yae_xcorr_via_rdft	(	FFTSample *	xcorr,
		RDFTContext *	complex_to_real,
		const FFTComplex *	xa,
		const FFTComplex *	xb,
		const int	window
	)			`[static]`

Calculate cross-correlation via rDFT.

Multiply two vectors of complex numbers (result of real_to_complex rDFT) and transform back via complex_to_real rDFT.

Definition at line 588 of file af_atempo.c.

Referenced by yae_align().

Variable Documentation

AVFilter avfilter_af_atempo

Initial value:

 {
    .name            = "atempo",
    .description     = NULL_IF_CONFIG_SMALL("Adjust audio tempo."),
    .init            = init,
    .uninit          = uninit,
    .query_formats   = query_formats,
    .process_command = process_command,
    .priv_size       = sizeof(ATempoContext),

    .inputs    = (const AVFilterPad[]) {
        { .name            = "default",
          .type            = AVMEDIA_TYPE_AUDIO,
          .filter_samples  = filter_samples,
          .config_props    = config_props,
          .min_perms       = AV_PERM_READ, },
        { .name = NULL}
    },

    .outputs   = (const AVFilterPad[]) {
        { .name            = "default",
          .request_frame   = request_frame,
          .type            = AVMEDIA_TYPE_AUDIO, },
        { .name = NULL}
    },
}

Definition at line 1139 of file af_atempo.c.


Data Structures
struct	AudioFragment
	A fragment of audio waveform. More...
struct	ATempoContext
	Filter state machine. More...
Defines
#define	RE_MALLOC_OR_FAIL(field, field_size)
#define	yae_init_xdat(scalar_type, scalar_max)
	A helper macro for initializing complex data buffer with scalar data of a given type.
#define	yae_blend(scalar_type)
	A helper macro for blending the overlap region of previous and current audio fragment.
Enumerations
enum	FilterState { YAE_LOAD_FRAGMENT, YAE_ADJUST_POSITION, YAE_RELOAD_FRAGMENT, YAE_OUTPUT_OVERLAP_ADD, YAE_FLUSH_OUTPUT }
	Filter state machine states. More...
Functions
static void	yae_clear (ATempoContext *atempo)
	Reset filter to initial state, do not deallocate existing local buffers.
static void	yae_release_buffers (ATempoContext *atempo)
	Reset filter to initial state and deallocate all buffers.
static int	yae_reset (ATempoContext *atempo, enum AVSampleFormat format, int sample_rate, int channels)
	Prepare filter for processing audio data of given format, sample rate and number of channels.
static int	yae_set_tempo (AVFilterContext ctx, const char arg_tempo)
static AudioFragment *	yae_curr_frag (ATempoContext *atempo)
static AudioFragment *	yae_prev_frag (ATempoContext *atempo)
static void	yae_downmix (ATempoContext atempo, AudioFragment frag)
	Initialize complex data buffer of a given audio fragment with down-mixed mono data of appropriate scalar type.
static int	yae_load_data (ATempoContext atempo, const uint8_t src_ref, const uint8_t src_end, int64_t stop_here)
	Populate the internal data buffer on as-needed basis.
static int	yae_load_frag (ATempoContext atempo, const uint8_t src_ref, const uint8_t src_end)
	Populate current audio fragment data buffer.
static void	yae_advance_to_next_frag (ATempoContext *atempo)
	Prepare for loading next audio fragment.
static void	yae_xcorr_via_rdft (FFTSample xcorr, RDFTContext complex_to_real, const FFTComplex xa, const FFTComplex xb, const int window)
	Calculate cross-correlation via rDFT.
static int	yae_align (AudioFragment frag, const AudioFragment prev, const int window, const int delta_max, const int drift, FFTSample correlation, RDFTContext complex_to_real)
	Calculate alignment offset for given fragment relative to the previous fragment.
static int	yae_adjust_position (ATempoContext *atempo)
	Adjust current fragment position for better alignment with previous fragment.
static int	yae_overlap_add (ATempoContext atempo, uint8_t dst_ref, uint8_t dst_end)
	Blend the overlap region of previous and current audio fragment and output the results to the given destination buffer.
static void	yae_apply (ATempoContext atempo, const uint8_t src_ref, const uint8_t src_end, uint8_t *dst_ref, uint8_t dst_end)
	Feed as much data to the filter as it is able to consume and receive as much processed data in the destination buffer as it is able to produce or store.
static int	yae_flush (ATempoContext atempo, uint8_t dst_ref, uint8_t dst_end)
	Flush any buffered data from the filter.
static av_cold int	init (AVFilterContext ctx, const char args)
static av_cold void	uninit (AVFilterContext *ctx)
static int	query_formats (AVFilterContext *ctx)
static int	config_props (AVFilterLink *inlink)
static void	push_samples (ATempoContext atempo, AVFilterLink outlink, int n_out)
static int	filter_samples (AVFilterLink inlink, AVFilterBufferRef src_buffer)
static int	request_frame (AVFilterLink *outlink)
static int	process_command (AVFilterContext ctx, const char cmd, const char arg, char res, int res_len, int flags)
Variables
AVFilter	avfilter_af_atempo