libavcodec/canopus.c

   1 /*
   2  * Canopus common routines
   3  * Copyright (c) 2015 Vittorio Giovara <vittorio.giovara@gmail.com>
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * Libav is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with Libav; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include <stdint.h>
  23
  24 #include "libavutil/rational.h"
  25
  26 #include "avcodec.h"
  27 #include "bytestream.h"
  28 #include "canopus.h"
  29
  30 int ff_canopus_parse_info_tag(AVCodecContext *avctx,
  31                               const uint8_t *src, size_t size)
  32 {
  33     GetByteContext gbc;
  34     int par_x, par_y, field_order;
  35
  36     bytestream2_init(&gbc, src, size);
  37
  38     /* Parse aspect ratio. */
  39     bytestream2_skip(&gbc, 8); // unknown, 16 bits 1
  40     par_x = bytestream2_get_le32(&gbc);
  41     par_y = bytestream2_get_le32(&gbc);
  42     if (par_x && par_y)
  43         av_reduce(&avctx->sample_aspect_ratio.num,
  44                   &avctx->sample_aspect_ratio.den,
  45                   par_x, par_y, 255);
  46
  47     /* Short INFO tag (used in CLLC) has only AR data. */
  48     if (size == 0x18)
  49         return 0;
  50
  51     bytestream2_skip(&gbc, 16); // unknown RDRT tag
  52
  53     /* Parse FIEL tag. */
  54     bytestream2_skip(&gbc, 8); // 'FIEL' and 4 bytes 0
  55     field_order = bytestream2_get_le32(&gbc);
  56     switch (field_order) {
  57     case 0: avctx->field_order = AV_FIELD_TT; break;
  58     case 1: avctx->field_order = AV_FIELD_BB; break;
  59     case 2: avctx->field_order = AV_FIELD_PROGRESSIVE; break;
  60     }
  61
  62     return 0;
  63 }