/*
  * Copyright (c) 2003 Rich Felker
  * 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
  * field filter, based on libmpcodecs/vf_field.c by Rich Felker
  */
 
 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
 #include "avfilter.h"
 #include "internal.h"
 
 enum FieldType { FIELD_TYPE_TOP = 0, FIELD_TYPE_BOTTOM };
 
 typedef struct {
     const AVClass *class;
     enum FieldType type;
     int nb_planes;              ///< number of planes of the current format
 } FieldContext;
 
 #define OFFSET(x) offsetof(FieldContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 
 static const AVOption field_options[] = {
     {"type", "set field type (top or bottom)", OFFSET(type), AV_OPT_TYPE_INT, {.i64=FIELD_TYPE_TOP}, 0, 1, FLAGS, "field_type" },
     {"top",    "select top field",    0, AV_OPT_TYPE_CONST, {.i64=FIELD_TYPE_TOP},    INT_MIN, INT_MAX, FLAGS, "field_type"},
     {"bottom", "select bottom field", 0, AV_OPT_TYPE_CONST, {.i64=FIELD_TYPE_BOTTOM}, INT_MIN, INT_MAX, FLAGS, "field_type"},
     {NULL}
 };
 
 AVFILTER_DEFINE_CLASS(field);
 
 static int config_props_output(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     FieldContext *field = ctx->priv;
     AVFilterLink *inlink = ctx->inputs[0];
 

     field->nb_planes = av_pix_fmt_count_planes(outlink->format);

 
     outlink->w = inlink->w;
     outlink->h = (inlink->h + (field->type == FIELD_TYPE_TOP)) / 2;
 
     av_log(ctx, AV_LOG_VERBOSE, "w:%d h:%d type:%s -> w:%d h:%d\n",
            inlink->w, inlink->h, field->type == FIELD_TYPE_BOTTOM ? "bottom" : "top",
            outlink->w, outlink->h);
     return 0;
 }
 

 static int filter_frame(AVFilterLink *inlink, AVFrame *inpicref)

 {
     FieldContext *field = inlink->dst->priv;
     AVFilterLink *outlink = inlink->dst->outputs[0];
     int i;
 

     inpicref->height = outlink->h;
     inpicref->interlaced_frame = 0;

 
     for (i = 0; i < field->nb_planes; i++) {
         if (field->type == FIELD_TYPE_BOTTOM)

             inpicref->data[i] = inpicref->data[i] + inpicref->linesize[i];
         inpicref->linesize[i] = 2 * inpicref->linesize[i];

     }

     return ff_filter_frame(outlink, inpicref);

 }
 
 static const AVFilterPad field_inputs[] = {
     {

         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .filter_frame = filter_frame,

     },
     { NULL }
 };
 
 static const AVFilterPad field_outputs[] = {
     {

         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .config_props = config_props_output,

     },
     { NULL }
 };
 
 AVFilter avfilter_vf_field = {

     .name        = "field",
     .description = NULL_IF_CONFIG_SMALL("Extract a field from the input video."),
     .priv_size   = sizeof(FieldContext),
     .inputs      = field_inputs,
     .outputs     = field_outputs,
     .priv_class  = &field_class,

 };