yading@10: /*
yading@10:  * Copyright (c) 2012 Stefano Sabatini
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file framestep filter, inspired on libmpcodecs/vf_framestep.c by
yading@10:  * Daniele Fornighieri <guru AT digitalfantasy it>.
yading@10:  */
yading@10: 
yading@10: #include "libavutil/opt.h"
yading@10: #include "avfilter.h"
yading@10: #include "internal.h"
yading@10: #include "video.h"
yading@10: 
yading@10: typedef struct {
yading@10:     const AVClass *class;
yading@10:     int frame_step, frame_count;
yading@10: } FrameStepContext;
yading@10: 
yading@10: #define OFFSET(x) offsetof(FrameStepContext, x)
yading@10: #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
yading@10: 
yading@10: static const AVOption framestep_options[] = {
yading@10:     { "step", "set frame step",  OFFSET(frame_step), AV_OPT_TYPE_INT, {.i64=1}, 1, INT_MAX, FLAGS},
yading@10:     {NULL},
yading@10: };
yading@10: 
yading@10: AVFILTER_DEFINE_CLASS(framestep);
yading@10: 
yading@10: static int config_output_props(AVFilterLink *outlink)
yading@10: {
yading@10:     AVFilterContext *ctx = outlink->src;
yading@10:     FrameStepContext *framestep = ctx->priv;
yading@10:     AVFilterLink *inlink = ctx->inputs[0];
yading@10: 
yading@10:     outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
yading@10:     outlink->frame_rate =
yading@10:         av_div_q(inlink->frame_rate, (AVRational){framestep->frame_step, 1});
yading@10: 
yading@10:     av_log(ctx, AV_LOG_VERBOSE, "step:%d frame_rate:%d/%d(%f) -> frame_rate:%d/%d(%f)\n",
yading@10:            framestep->frame_step,
yading@10:            inlink->frame_rate.num, inlink->frame_rate.den, av_q2d(inlink->frame_rate),
yading@10:            outlink->frame_rate.num, outlink->frame_rate.den, av_q2d(outlink->frame_rate));
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static int filter_frame(AVFilterLink *inlink, AVFrame *ref)
yading@10: {
yading@10:     FrameStepContext *framestep = inlink->dst->priv;
yading@10: 
yading@10:     if (!(framestep->frame_count++ % framestep->frame_step)) {
yading@10:         return ff_filter_frame(inlink->dst->outputs[0], ref);
yading@10:     } else {
yading@10:         av_frame_free(&ref);
yading@10:         return 0;
yading@10:     }
yading@10: }
yading@10: 
yading@10: static const AVFilterPad framestep_inputs[] = {
yading@10:     {
yading@10:         .name             = "default",
yading@10:         .type             = AVMEDIA_TYPE_VIDEO,
yading@10:         .filter_frame     = filter_frame,
yading@10:     },
yading@10:     { NULL }
yading@10: };
yading@10: 
yading@10: static const AVFilterPad framestep_outputs[] = {
yading@10:     {
yading@10:         .name          = "default",
yading@10:         .type          = AVMEDIA_TYPE_VIDEO,
yading@10:         .config_props  = config_output_props,
yading@10:     },
yading@10:     { NULL }
yading@10: };
yading@10: 
yading@10: AVFilter avfilter_vf_framestep = {
yading@10:     .name      = "framestep",
yading@10:     .description = NULL_IF_CONFIG_SMALL("Select one frame every N frames."),
yading@10:     .priv_size = sizeof(FrameStepContext),
yading@10:     .priv_class = &framestep_class,
yading@10:     .inputs    = framestep_inputs,
yading@10:     .outputs   = framestep_outputs,
yading@10: };