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/*
* Copyright (c) 2012 Stefano Sabatini
*
* 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 framestep filter, inspired on libmpcodecs/vf_framestep.c by
* Daniele Fornighieri <guru AT digitalfantasy it>.
*/
#include "avfilter.h"
#include "internal.h"
#include "video.h"
typedef struct {
int frame_step, frame_count, frame_selected;
} FrameStepContext;
static av_cold int init(AVFilterContext *ctx, const char *args)
{
FrameStepContext *framestep = ctx->priv;
char *tailptr;
long int n = 1;
if (args) {
n = strtol(args, &tailptr, 10);
if (*tailptr || n <= 0 || n >= INT_MAX) {
av_log(ctx, AV_LOG_ERROR,
"Invalid argument '%s', must be a positive integer <= INT_MAX\n", args);
return AVERROR(EINVAL);
}
}
framestep->frame_step = n;
return 0;
}
static int config_output_props(AVFilterLink *outlink)
{
AVFilterContext *ctx = outlink->src;
FrameStepContext *framestep = ctx->priv;
AVFilterLink *inlink = ctx->inputs[0];
outlink->frame_rate =
av_div_q(inlink->frame_rate, (AVRational){framestep->frame_step, 1});
av_log(ctx, AV_LOG_VERBOSE, "step:%d frame_rate:%d/%d(%f) -> frame_rate:%d/%d(%f)\n",
framestep->frame_step,
inlink->frame_rate.num, inlink->frame_rate.den, av_q2d(inlink->frame_rate),
outlink->frame_rate.num, outlink->frame_rate.den, av_q2d(outlink->frame_rate));
return 0;
}
static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *ref)
{
FrameStepContext *framestep = inlink->dst->priv;
if (!(framestep->frame_count++ % framestep->frame_step)) {
framestep->frame_selected = 1;
return ff_filter_frame(inlink->dst->outputs[0], ref);
} else {
framestep->frame_selected = 0;
avfilter_unref_buffer(ref);
return 0;
}
}
static int request_frame(AVFilterLink *outlink)
{
FrameStepContext *framestep = outlink->src->priv;
AVFilterLink *inlink = outlink->src->inputs[0];
int ret;
framestep->frame_selected = 0;
do {
ret = ff_request_frame(inlink);
} while (!framestep->frame_selected && ret >= 0);
return ret;
}
static const AVFilterPad framestep_inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.get_video_buffer = ff_null_get_video_buffer,
.filter_frame = filter_frame,
},
{ NULL }
};
static const AVFilterPad framestep_outputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.config_props = config_output_props,
.request_frame = request_frame,
},
{ NULL }
};
AVFilter avfilter_vf_framestep = {
.name = "framestep",
.description = NULL_IF_CONFIG_SMALL("Select one frame every N frames."),
.init = init,
.priv_size = sizeof(FrameStepContext),
.inputs = framestep_inputs,
.outputs = framestep_outputs,
};
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