/*
  * Copyright (c) 2013 Paul B Mahol
  *
  * 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
  */
 
 #include "libavutil/pixdesc.h"
 #include "avfilter.h"
 #include "internal.h"
 
 typedef struct {
     int nb_planes;
     double ts_unit;
 } SeparateFieldsContext;
 
 static int config_props_output(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     SeparateFieldsContext *sf = ctx->priv;
     AVFilterLink *inlink = ctx->inputs[0];
 
     sf->nb_planes = av_pix_fmt_count_planes(inlink->format);;
 
     if (inlink->h & 1) {
         av_log(ctx, AV_LOG_ERROR, "height must be even\n");
         return AVERROR_INVALIDDATA;
     }
 

     outlink->time_base.num = inlink->time_base.num;
     outlink->time_base.den = inlink->time_base.den * 2;

     outlink->frame_rate.num = inlink->frame_rate.num * 2;
     outlink->frame_rate.den = inlink->frame_rate.den;
     outlink->w = inlink->w;
     outlink->h = inlink->h / 2;

     sf->ts_unit = av_q2d(av_inv_q(av_mul_q(outlink->frame_rate, outlink->time_base)));

 
     return 0;
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *inpicref)
 {
     AVFilterContext *ctx = inlink->dst;
     SeparateFieldsContext *sf = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFrame *second;
     int i, ret;
 
     inpicref->height = outlink->h;
     inpicref->interlaced_frame = 0;
 
     second = av_frame_clone(inpicref);
     if (!second)
         return AVERROR(ENOMEM);
 
     for (i = 0; i < sf->nb_planes; i++) {
         if (!inpicref->top_field_first)
             inpicref->data[i] = inpicref->data[i] + inpicref->linesize[i];
         else
             second->data[i] = second->data[i] + second->linesize[i];
         inpicref->linesize[i] *= 2;
         second->linesize[i]   *= 2;
     }
 

     inpicref->pts = outlink->frame_count * sf->ts_unit;

     ret = ff_filter_frame(outlink, inpicref);
     if (ret < 0)
         return ret;

 
     second->pts = outlink->frame_count * sf->ts_unit;

     return ff_filter_frame(outlink, second);
 }
 
 static const AVFilterPad separatefields_inputs[] = {
     {
         .name             = "default",
         .type             = AVMEDIA_TYPE_VIDEO,
         .filter_frame     = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad separatefields_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_VIDEO,
         .config_props  = config_props_output,
     },
     { NULL }
 };
 
 AVFilter avfilter_vf_separatefields = {
     .name          = "separatefields",
     .description   = NULL_IF_CONFIG_SMALL("Split input video frames into fields."),
     .priv_size     = sizeof(SeparateFieldsContext),
     .inputs        = separatefields_inputs,
     .outputs       = separatefields_outputs,
 };