vf_dejudder.c File Reference

remove judder in video stream More...

#include "libavutil/opt.h"
#include "libavutil/mathematics.h"
#include "avfilter.h"
#include "internal.h"
#include "video.h"

Go to the source code of this file.

Data Structures
struct	DejudderContext

Macros
#define	OFFSET(x)   offsetof(DejudderContext, x)
#define	FLAGS   AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM

Functions
	AVFILTER_DEFINE_CLASS (dejudder)
static int	config_out_props (AVFilterLink *outlink)
static av_cold int	dejudder_init (AVFilterContext *ctx)
static av_cold void	dejudder_uninit (AVFilterContext *ctx)
static int	filter_frame (AVFilterLink *inlink, AVFrame *frame)

Variables
static const AVOption	dejudder_options []
static const AVFilterPad	dejudder_inputs []
static const AVFilterPad	dejudder_outputs []
AVFilter	ff_vf_dejudder

Detailed Description

remove judder in video stream

Algorithm:

• If the old packets had PTS of old_pts[i]. Replace these with new value based on the running average of the last n=cycle frames. So

  new_pts[i] = Sum(k=i-n+1, i, old_pts[k])/n

  • (old_pts[i]-old_pts[i-n])*(n-1)/2n

  For any repeating pattern of length n of judder this will produce an even progression of PTS's.

• In order to avoid calculating this sum ever frame, a running tally is maintained in ctx->new_pts. Each frame the new term at the start of the sum is added, the one and the end is removed, and the offset terms (second line in formula above) are recalculated.
• To aid in this a ringbuffer of the last n-2 PTS's is maintained in ctx->ringbuff. With the indices of the first two and last two entries stored in i1, i2, i3, & i4.
• To ensure that the new PTS's are integers, time_base is divided by 2n. This removes the division in the new_pts calculation.
• frame_rate is also multiplied by 2n to allow the frames to fall where they may in what may now be a VFR output. This produces more even output then setting frame_rate=1/0 in practice.

Definition in file vf_dejudder.c.

Macro Definition Documentation

#define OFFSET

(

x

)

offsetof(DejudderContext, x)

Definition at line 69 of file vf_dejudder.c.

#define FLAGS   AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM

Definition at line 70 of file vf_dejudder.c.

Function Documentation

AVFILTER_DEFINE_CLASS

(

dejudder

)

static int config_out_props ( AVFilterLink *  outlink )

static

Definition at line 80 of file vf_dejudder.c.

static av_cold int dejudder_init ( AVFilterContext *  ctx )

static

Definition at line 94 of file vf_dejudder.c.

static av_cold void dejudder_uninit ( AVFilterContext *  ctx )

static

Definition at line 112 of file vf_dejudder.c.

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

static

Definition at line 119 of file vf_dejudder.c.

Variable Documentation

const AVOption dejudder_options[]

static

Initial value:

= {
    {"cycle", "set the length of the cycle to use for dejuddering",
        OFFSET(cycle), AV_OPT_TYPE_INT, {.i64 = 4}, 2, 240, .flags = FLAGS},
    {NULL}
}

Definition at line 72 of file vf_dejudder.c.

const AVFilterPad dejudder_inputs[]

static

Initial value:

= {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_VIDEO,
        .filter_frame = filter_frame,
    },
    { NULL }
}

Definition at line 160 of file vf_dejudder.c.

const AVFilterPad dejudder_outputs[]

static

Initial value:

= {
    {
        .name = "default",
        .type = AVMEDIA_TYPE_VIDEO,
        .config_props = config_out_props,
    },
    { NULL }
}

Definition at line 169 of file vf_dejudder.c.

AVFilter ff_vf_dejudder

Initial value:

= {
    .name        = "dejudder",
    .description = NULL_IF_CONFIG_SMALL("Remove judder produced by pullup."),
    .priv_size   = sizeof(DejudderContext),
    .priv_class  = &dejudder_class,
    .inputs      = dejudder_inputs,
    .outputs     = dejudder_outputs,
    .init        = dejudder_init,
    .uninit      = dejudder_uninit,
}

Definition at line 178 of file vf_dejudder.c.