/*
  * Mpeg video formats-related defines and utility functions
  *

  * 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 <stdint.h>
 
 #include "libavutil/common.h"
 #include "libavutil/frame.h"
 #include "libavutil/pixdesc.h"
 
 #include "avcodec.h"
 #include "mpegutils.h"
 
 void ff_draw_horiz_band(AVCodecContext *avctx,
                         AVFrame *cur, AVFrame *last,
                         int y, int h, int picture_structure,
                         int first_field, int low_delay)
 {
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
     int vshift = desc->log2_chroma_h;
     const int field_pic = picture_structure != PICT_FRAME;
     if (field_pic) {
         h <<= 1;
         y <<= 1;
     }
 
     h = FFMIN(h, avctx->height - y);
 
     if (field_pic && first_field &&
         !(avctx->slice_flags & SLICE_FLAG_ALLOW_FIELD))
         return;
 
     if (avctx->draw_horiz_band) {
         AVFrame *src;
         int offset[AV_NUM_DATA_POINTERS];
         int i;
 
         if (cur->pict_type == AV_PICTURE_TYPE_B || low_delay ||
            (avctx->slice_flags & SLICE_FLAG_CODED_ORDER))
             src = cur;
         else if (last)
             src = last;
         else
             return;
 
         if (cur->pict_type == AV_PICTURE_TYPE_B &&
             picture_structure == PICT_FRAME &&
             avctx->codec_id != AV_CODEC_ID_SVQ3) {
             for (i = 0; i < AV_NUM_DATA_POINTERS; i++)
                 offset[i] = 0;
         } else {
             offset[0]= y * src->linesize[0];
             offset[1]=
             offset[2]= (y >> vshift) * src->linesize[1];
             for (i = 3; i < AV_NUM_DATA_POINTERS; i++)
                 offset[i] = 0;
         }
 
         emms_c();
 
         avctx->draw_horiz_band(avctx, src, offset,
                                y, picture_structure, h);
     }
 }