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/*
* Copyright (c) 2014 Nicholas Robbins
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* 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.
*/
#include "libavutil/opt.h"
#include "libavutil/mathematics.h"
#include "avfilter.h"
#include "internal.h"
#include "video.h"
typedef struct {
const AVClass *class;
int64_t *ringbuff;
int i1, i2, i3, i4;
int64_t new_pts;
int start_count;
/* options */
int cycle;
} DejudderContext;
#define OFFSET(x) offsetof(DejudderContext, x)
#define FLAGS AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM
static const AVOption dejudder_options[] = {
{"cycle", "set the length of the cycle to use for dejuddering",
OFFSET(cycle), AV_OPT_TYPE_INT, {.i64 = 4}, 2, 240, .flags = FLAGS},
{NULL}
};
AVFILTER_DEFINE_CLASS(dejudder);
static int config_out_props(AVFilterLink *outlink)
{
AVFilterContext *ctx = outlink->src;
DejudderContext *s = ctx->priv;
AVFilterLink *inlink = outlink->src->inputs[0];
outlink->time_base = av_mul_q(inlink->time_base, av_make_q(1, 2 * s->cycle));
outlink->frame_rate = av_mul_q(inlink->frame_rate, av_make_q(2 * s->cycle, 1));
av_log(ctx, AV_LOG_VERBOSE, "cycle:%d\n", s->cycle);
return 0;
}
static av_cold int dejudder_init(AVFilterContext *ctx)
{
DejudderContext *s = ctx->priv;
s->ringbuff = av_mallocz_array(s->cycle+2, sizeof(*s->ringbuff));
if (!s->ringbuff)
return AVERROR(ENOMEM);
s->new_pts = 0;
s->i1 = 0;
s->i2 = 1;
s->i3 = 2;
s->i4 = 3;
s->start_count = s->cycle + 2;
return 0;
}
static av_cold void dejudder_uninit(AVFilterContext *ctx)
{
DejudderContext *s = ctx->priv;
av_freep(&(s->ringbuff));
}
static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
{
int k;
AVFilterContext *ctx = inlink->dst;
AVFilterLink *outlink = ctx->outputs[0];
DejudderContext *s = ctx->priv;
int64_t *judbuff = s->ringbuff;
int64_t next_pts = frame->pts;
int64_t offset;
if (next_pts == AV_NOPTS_VALUE)
return ff_filter_frame(outlink, frame);
if (s->start_count) {
s->start_count--;
s->new_pts = next_pts * 2 * s->cycle;
} else {
if (next_pts < judbuff[s->i2]) {
offset = next_pts + judbuff[s->i3] - judbuff[s->i4] - judbuff[s->i1];
for (k = 0; k < s->cycle + 2; k++)
judbuff[k] += offset;
}
s->new_pts += (s->cycle - 1) * (judbuff[s->i3] - judbuff[s->i1])
+ (s->cycle + 1) * (next_pts - judbuff[s->i4]);
}
judbuff[s->i2] = next_pts;
s->i1 = s->i2;
s->i2 = s->i3;
s->i3 = s->i4;
s->i4 = (s->i4 + 1) % (s->cycle + 2);
frame->pts = s->new_pts;
for (k = 0; k < s->cycle + 2; k++)
av_log(ctx, AV_LOG_DEBUG, "%"PRId64"\t", judbuff[k]);
av_log(ctx, AV_LOG_DEBUG, "next=%"PRId64", new=%"PRId64"\n", next_pts, frame->pts);
return ff_filter_frame(outlink, frame);
}
static const AVFilterPad dejudder_inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.filter_frame = filter_frame,
},
{ NULL }
};
static const AVFilterPad dejudder_outputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.config_props = config_out_props,
},
{ NULL }
};
AVFilter ff_vf_dejudder = {
.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,
};
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