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![Paul B Mahol](/assets/img/avatar_default.png)
This is shorter and consistent across filters. Signed-off-by: Paul B Mahol <onemda@gmail.com>
188 lines
5.5 KiB
C
188 lines
5.5 KiB
C
/*
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* Copyright (c) 2014 Nicholas Robbins
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* remove judder in video stream
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*
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* Algorithm:
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* - If the old packets had PTS of old_pts[i]. Replace these with new
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* value based on the running average of the last n=cycle frames. So
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*
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* new_pts[i] = Sum(k=i-n+1, i, old_pts[k])/n
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* + (old_pts[i]-old_pts[i-n])*(n-1)/2n
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*
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* For any repeating pattern of length n of judder this will produce
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* an even progression of PTS's.
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*
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* - In order to avoid calculating this sum ever frame, a running tally
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* is maintained in ctx->new_pts. Each frame the new term at the start
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* of the sum is added, the one and the end is removed, and the offset
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* terms (second line in formula above) are recalculated.
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*
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* - To aid in this a ringbuffer of the last n-2 PTS's is maintained in
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* ctx->ringbuff. With the indices of the first two and last two entries
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* stored in i1, i2, i3, & i4.
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*
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* - To ensure that the new PTS's are integers, time_base is divided
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* by 2n. This removes the division in the new_pts calculation.
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*
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* - frame_rate is also multiplied by 2n to allow the frames to fall
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* where they may in what may now be a VFR output. This produces more
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* even output then setting frame_rate=1/0 in practice.
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*/
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#include "libavutil/opt.h"
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#include "libavutil/mathematics.h"
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#include "avfilter.h"
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#include "internal.h"
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#include "video.h"
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typedef struct {
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const AVClass *class;
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int64_t *ringbuff;
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int i1, i2, i3, i4;
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int64_t new_pts;
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int start_count;
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/* options */
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int cycle;
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} DejudderContext;
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#define OFFSET(x) offsetof(DejudderContext, x)
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#define FLAGS AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM
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static const AVOption dejudder_options[] = {
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{"cycle", "set the length of the cycle to use for dejuddering",
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OFFSET(cycle), AV_OPT_TYPE_INT, {.i64 = 4}, 2, 240, .flags = FLAGS},
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{NULL}
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};
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AVFILTER_DEFINE_CLASS(dejudder);
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static int config_out_props(AVFilterLink *outlink)
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{
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AVFilterContext *ctx = outlink->src;
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DejudderContext *s = ctx->priv;
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AVFilterLink *inlink = outlink->src->inputs[0];
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outlink->time_base = av_mul_q(inlink->time_base, av_make_q(1, 2 * s->cycle));
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outlink->frame_rate = av_mul_q(inlink->frame_rate, av_make_q(2 * s->cycle, 1));
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av_log(ctx, AV_LOG_VERBOSE, "cycle:%d\n", s->cycle);
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return 0;
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}
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static av_cold int dejudder_init(AVFilterContext *ctx)
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{
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DejudderContext *s = ctx->priv;
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s->ringbuff = av_mallocz_array(s->cycle+2, sizeof(*s->ringbuff));
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if (!s->ringbuff)
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return AVERROR(ENOMEM);
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s->new_pts = 0;
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s->i1 = 0;
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s->i2 = 1;
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s->i3 = 2;
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s->i4 = 3;
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s->start_count = s->cycle + 2;
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return 0;
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}
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static av_cold void dejudder_uninit(AVFilterContext *ctx)
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{
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DejudderContext *s = ctx->priv;
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av_freep(&(s->ringbuff));
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}
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static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
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{
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int k;
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AVFilterContext *ctx = inlink->dst;
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AVFilterLink *outlink = ctx->outputs[0];
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DejudderContext *s = ctx->priv;
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int64_t *judbuff = s->ringbuff;
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int64_t next_pts = frame->pts;
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int64_t offset;
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if (next_pts == AV_NOPTS_VALUE)
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return ff_filter_frame(outlink, frame);
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if (s->start_count) {
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s->start_count--;
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s->new_pts = next_pts * 2 * s->cycle;
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} else {
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if (next_pts < judbuff[s->i2]) {
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offset = next_pts + judbuff[s->i3] - judbuff[s->i4] - judbuff[s->i1];
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for (k = 0; k < s->cycle + 2; k++)
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judbuff[k] += offset;
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}
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s->new_pts += (s->cycle - 1) * (judbuff[s->i3] - judbuff[s->i1])
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+ (s->cycle + 1) * (next_pts - judbuff[s->i4]);
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}
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judbuff[s->i2] = next_pts;
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s->i1 = s->i2;
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s->i2 = s->i3;
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s->i3 = s->i4;
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s->i4 = (s->i4 + 1) % (s->cycle + 2);
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frame->pts = s->new_pts;
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for (k = 0; k < s->cycle + 2; k++)
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av_log(ctx, AV_LOG_DEBUG, "%"PRId64"\t", judbuff[k]);
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av_log(ctx, AV_LOG_DEBUG, "next=%"PRId64", new=%"PRId64"\n", next_pts, frame->pts);
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return ff_filter_frame(outlink, frame);
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}
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static const AVFilterPad dejudder_inputs[] = {
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{
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.name = "default",
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.type = AVMEDIA_TYPE_VIDEO,
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.filter_frame = filter_frame,
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},
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{ NULL }
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};
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static const AVFilterPad dejudder_outputs[] = {
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{
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.name = "default",
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.type = AVMEDIA_TYPE_VIDEO,
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.config_props = config_out_props,
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},
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{ NULL }
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};
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AVFilter ff_vf_dejudder = {
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.name = "dejudder",
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.description = NULL_IF_CONFIG_SMALL("Remove judder produced by pullup."),
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.priv_size = sizeof(DejudderContext),
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.priv_class = &dejudder_class,
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.inputs = dejudder_inputs,
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.outputs = dejudder_outputs,
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.init = dejudder_init,
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.uninit = dejudder_uninit,
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};
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