af_atempo.c File Reference

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

#include <float.h>
#include "libavutil/avassert.h"
#include "libavutil/channel_layout.h"
#include "libavutil/mem.h"
#include "libavutil/opt.h"
#include "libavutil/samplefmt.h"
#include "libavutil/tx.h"
#include "avfilter.h"
#include "audio.h"
#include "filters.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...

Macros
#define	YAE_ATEMPO_MIN   0.5
#define	YAE_ATEMPO_MAX   100.0
#define	OFFSET(x)
#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
	AVFILTER_DEFINE_CLASS (atempo)
static AudioFragment *	yae_curr_frag (ATempoContext *atempo)
static AudioFragment *	yae_prev_frag (ATempoContext *atempo)
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_update (AVFilterContext *ctx)
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 (float *xcorr_in, float *xcorr, AVTXContext *complex_to_real, av_tx_fn c2r_fn, const AVComplexFloat *xa, const AVComplexFloat *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, float *correlation_in, float *correlation, AVTXContext *complex_to_real, av_tx_fn c2r_fn)
	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)
static av_cold void	uninit (AVFilterContext *ctx)
static int	config_props (AVFilterLink *inlink)
static int	push_samples (ATempoContext *atempo, AVFilterLink *outlink, int n_out)
static int	filter_frame (AVFilterLink *inlink, AVFrame *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
static const AVOption	atempo_options []
static enum AVSampleFormat	sample_fmts []
static const AVFilterPad	atempo_inputs []
static const AVFilterPad	atempo_outputs []
const FFFilter	ff_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.

Macro Definition Documentation

YAE_ATEMPO_MIN

#define YAE_ATEMPO_MIN   0.5

Definition at line 157 of file af_atempo.c.

YAE_ATEMPO_MAX

#define YAE_ATEMPO_MAX   100.0

Definition at line 158 of file af_atempo.c.

OFFSET

#define OFFSET

(

x

)

Value:

offsetof(ATempoContext, x)

Definition at line 160 of file af_atempo.c.

yae_init_xdat

#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 353 of file af_atempo.c.

Referenced by yae_downmix().

yae_blend

#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 732 of file af_atempo.c.

Referenced by yae_overlap_add().

Enumeration Type Documentation

FilterState

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

AVFILTER_DEFINE_CLASS()

AVFILTER_DEFINE_CLASS

(

atempo

)

yae_curr_frag()

static AudioFragment * yae_curr_frag ( ATempoContext * atempo )

inlinestatic

Definition at line 173 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().

yae_prev_frag()

static AudioFragment * yae_prev_frag ( ATempoContext * atempo )

inlinestatic

Definition at line 178 of file af_atempo.c.

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

yae_clear()

static void yae_clear ( ATempoContext * atempo )

static

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

Definition at line 186 of file af_atempo.c.

Referenced by yae_release_buffers().

yae_release_buffers()

static void yae_release_buffers ( ATempoContext * atempo )

static

Reset filter to initial state and deallocate all buffers.

Definition at line 227 of file af_atempo.c.

Referenced by uninit(), and yae_reset().

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 251 of file af_atempo.c.

Referenced by config_props().

yae_update()

static int yae_update ( AVFilterContext * ctx )

static

Definition at line 338 of file af_atempo.c.

Referenced by process_command().

yae_downmix()

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 403 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

yae_load_data()

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 431 of file af_atempo.c.

Referenced by yae_load_frag().

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 506 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

yae_advance_to_next_frag()

static void yae_advance_to_next_frag ( ATempoContext * atempo )

static

Prepare for loading next audio fragment.

Definition at line 586 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

yae_xcorr_via_rdft()

static void yae_xcorr_via_rdft ( float * xcorr_in, float * xcorr, AVTXContext * complex_to_real, av_tx_fn c2r_fn, const AVComplexFloat * xa, const AVComplexFloat * 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 608 of file af_atempo.c.

Referenced by yae_align().

yae_align()

static int yae_align ( AudioFragment * frag, const AudioFragment * prev, const int window, const int delta_max, const int drift, float * correlation_in, float * correlation, AVTXContext * complex_to_real, av_tx_fn c2r_fn )

static

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

Returns

alignment offset of current fragment relative to previous.

Definition at line 634 of file af_atempo.c.

Referenced by yae_adjust_position().

yae_adjust_position()

static int yae_adjust_position ( ATempoContext * atempo )

static

Adjust current fragment position for better alignment with previous fragment.

Returns

alignment correction.

Definition at line 692 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

yae_overlap_add()

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 769 of file af_atempo.c.

Referenced by yae_apply(), and yae_flush().

yae_apply()

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 824 of file af_atempo.c.

Referenced by filter_frame().

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 898 of file af_atempo.c.

Referenced by request_frame().

init()

static av_cold int init ( AVFilterContext * ctx )

static

Definition at line 987 of file af_atempo.c.

uninit()

static av_cold void uninit ( AVFilterContext * ctx )

static

Definition at line 995 of file af_atempo.c.

config_props()

static int config_props ( AVFilterLink * inlink )

static

Definition at line 1016 of file af_atempo.c.

push_samples()

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

static

Definition at line 1027 of file af_atempo.c.

Referenced by filter_frame(), and request_frame().

filter_frame()

static int filter_frame ( AVFilterLink * inlink, AVFrame * src_buffer )

static

Definition at line 1053 of file af_atempo.c.

request_frame()

static int request_frame ( AVFilterLink * outlink )

static

Definition at line 1101 of file af_atempo.c.

process_command()

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

static

Definition at line 1147 of file af_atempo.c.

Variable Documentation

atempo_options

const AVOption atempo_options[]

static

Initial value:

= {
    { "tempo", "set tempo scale factor",
      OFFSET(tempo), AV_OPT_TYPE_DOUBLE, { .dbl = 1.0 },
      YAE_ATEMPO_MIN,
      YAE_ATEMPO_MAX,
      AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_RUNTIME_PARAM },
    { NULL }
}

Definition at line 162 of file af_atempo.c.

sample_fmts

enum AVSampleFormat sample_fmts[]

static

Initial value:

= {
    AV_SAMPLE_FMT_U8,
    AV_SAMPLE_FMT_S16,
    AV_SAMPLE_FMT_S32,
    AV_SAMPLE_FMT_FLT,
    AV_SAMPLE_FMT_DBL,
    AV_SAMPLE_FMT_NONE
}

Definition at line 1007 of file af_atempo.c.

atempo_inputs

const AVFilterPad atempo_inputs[]

static

Initial value:

= {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_AUDIO,
        .filter_frame = filter_frame,
        .config_props = config_props,
    },
}

Definition at line 1162 of file af_atempo.c.

atempo_outputs

const AVFilterPad atempo_outputs[]

static

Initial value:

= {
    {
        .name          = "default",
        .request_frame = request_frame,
        .type          = AVMEDIA_TYPE_AUDIO,
    },
}

Definition at line 1171 of file af_atempo.c.

ff_af_atempo

const FFFilter ff_af_atempo

Initial value:

= {
    .p.name          = "atempo",
    .p.description   = NULL_IF_CONFIG_SMALL("Adjust audio tempo."),
    .p.priv_class    = &atempo_class,
    .init            = init,
    .uninit          = uninit,
    .process_command = process_command,
    .priv_size       = sizeof(ATempoContext),
    FILTER_INPUTS(atempo_inputs),
    FILTER_OUTPUTS(atempo_outputs),
    FILTER_SAMPLEFMTS_ARRAY(sample_fmts),
}

Definition at line 1179 of file af_atempo.c.