2 * Copyright (c) 2012 Stefano Sabatini
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 * @file framestep filter, inspired on libmpcodecs/vf_framestep.c by
23 * Daniele Fornighieri <guru AT digitalfantasy it>.
26 #include "libavutil/opt.h"
33 int frame_step, frame_count;
36 #define OFFSET(x) offsetof(FrameStepContext, x)
37 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
39 static const AVOption framestep_options[] = {
40 { "step", "set frame step", OFFSET(frame_step), AV_OPT_TYPE_INT, {.i64=1}, 1, INT_MAX, FLAGS},
44 AVFILTER_DEFINE_CLASS(framestep);
46 static int config_output_props(AVFilterLink *outlink)
48 AVFilterContext *ctx = outlink->src;
49 FrameStepContext *framestep = ctx->priv;
50 AVFilterLink *inlink = ctx->inputs[0];
52 outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
54 av_div_q(inlink->frame_rate, (AVRational){framestep->frame_step, 1});
56 av_log(ctx, AV_LOG_VERBOSE, "step:%d frame_rate:%d/%d(%f) -> frame_rate:%d/%d(%f)\n",
57 framestep->frame_step,
58 inlink->frame_rate.num, inlink->frame_rate.den, av_q2d(inlink->frame_rate),
59 outlink->frame_rate.num, outlink->frame_rate.den, av_q2d(outlink->frame_rate));
63 static int filter_frame(AVFilterLink *inlink, AVFrame *ref)
65 FrameStepContext *framestep = inlink->dst->priv;
67 if (!(framestep->frame_count++ % framestep->frame_step)) {
68 return ff_filter_frame(inlink->dst->outputs[0], ref);
75 static const AVFilterPad framestep_inputs[] = {
78 .type = AVMEDIA_TYPE_VIDEO,
79 .filter_frame = filter_frame,
84 static const AVFilterPad framestep_outputs[] = {
87 .type = AVMEDIA_TYPE_VIDEO,
88 .config_props = config_output_props,
93 AVFilter avfilter_vf_framestep = {
95 .description = NULL_IF_CONFIG_SMALL("Select one frame every N frames."),
96 .priv_size = sizeof(FrameStepContext),
97 .priv_class = &framestep_class,
98 .inputs = framestep_inputs,
99 .outputs = framestep_outputs,