libmpdemux/yuv4mpeg_ratio.c

   1 /*
   2  *  yuv4mpeg_ratio.c:  Functions for dealing with y4m_ratio_t datatype.
   3  *
   4  *  Copyright (C) 2001 Matthew J. Marjanovic <maddog@mir.com>
   5  *
   6  *  This file is part of the MJPEG Tools package (mjpeg.sourceforge.net).
   7  *
   8  *  This program is free software; you can redistribute it and/or
   9  *  modify it under the terms of the GNU General Public License
  10  *  as published by the Free Software Foundation; either version 2
  11  *  of the License, or (at your option) any later version.
  12  *
  13  *  This program is distributed in the hope that it will be useful,
  14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *  GNU General Public License for more details.
  17  *
  18  *  You should have received a copy of the GNU General Public License
  19  *  along with this program; if not, write to the Free Software
  20  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  *
  22  */
  23
  24 #include "config.h"
  25
  26 #include <string.h>
  27 #include "yuv4mpeg.h"
  28 #include "yuv4mpeg_intern.h"
  29
  30
  31 /* useful list of standard framerates */
  32 const y4m_ratio_t y4m_fps_UNKNOWN    = Y4M_FPS_UNKNOWN;
  33 const y4m_ratio_t y4m_fps_NTSC_FILM  = Y4M_FPS_NTSC_FILM;
  34 const y4m_ratio_t y4m_fps_FILM       = Y4M_FPS_FILM;
  35 const y4m_ratio_t y4m_fps_PAL        = Y4M_FPS_PAL;
  36 const y4m_ratio_t y4m_fps_NTSC       = Y4M_FPS_NTSC;
  37 const y4m_ratio_t y4m_fps_30         = Y4M_FPS_30;
  38 const y4m_ratio_t y4m_fps_PAL_FIELD  = Y4M_FPS_PAL_FIELD;
  39 const y4m_ratio_t y4m_fps_NTSC_FIELD = Y4M_FPS_NTSC_FIELD;
  40 const y4m_ratio_t y4m_fps_60         = Y4M_FPS_60;
  41
  42 /* useful list of standard pixel aspect ratios */
  43 const y4m_ratio_t y4m_sar_UNKNOWN        = Y4M_SAR_UNKNOWN;
  44 const y4m_ratio_t y4m_sar_SQUARE         = Y4M_SAR_SQUARE;
  45 const y4m_ratio_t y4m_sar_NTSC_CCIR601   = Y4M_SAR_NTSC_CCIR601;
  46 const y4m_ratio_t y4m_sar_NTSC_16_9      = Y4M_SAR_NTSC_16_9;
  47 const y4m_ratio_t y4m_sar_NTSC_SVCD_4_3  = Y4M_SAR_NTSC_SVCD_4_3;
  48 const y4m_ratio_t y4m_sar_NTSC_SVCD_16_9 = Y4M_SAR_NTSC_SVCD_16_9;
  49 const y4m_ratio_t y4m_sar_PAL_CCIR601    = Y4M_SAR_PAL_CCIR601;
  50 const y4m_ratio_t y4m_sar_PAL_16_9       = Y4M_SAR_PAL_16_9;
  51 const y4m_ratio_t y4m_sar_PAL_SVCD_4_3   = Y4M_SAR_PAL_SVCD_4_3;
  52 const y4m_ratio_t y4m_sar_PAL_SVCD_16_9  = Y4M_SAR_PAL_SVCD_16_9;
  53
  54
  55 /*
  56  *  Euler's algorithm for greatest common divisor
  57  */
  58
  59 static int gcd(int a, int b)
  60 {
  61   a = (a >= 0) ? a : -a;
  62   b = (b >= 0) ? b : -b;
  63
  64   while (b > 0) {
  65     int x = b;
  66     b = a % b;
  67     a = x;
  68   }
  69   return a;
  70 }
  71
  72
  73 /*************************************************************************
  74  *
  75  * Remove common factors from a ratio
  76  *
  77  *************************************************************************/
  78
  79
  80 void y4m_ratio_reduce(y4m_ratio_t *r)
  81 {
  82   int d;
  83   if ((r->n == 0) && (r->d == 0)) return;  /* "unknown" */
  84   d = gcd(r->n, r->d);
  85   r->n /= d;
  86   r->d /= d;
  87 }
  88
  89
  90
  91 /*************************************************************************
  92  *
  93  * Parse "nnn:ddd" into a ratio
  94  *
  95  * returns:         Y4M_OK  - success
  96  *           Y4M_ERR_RANGE  - range error
  97  *
  98  *************************************************************************/
  99
 100 int y4m_parse_ratio(y4m_ratio_t *r, const char *s)
 101 {
 102   char *t = strchr(s, ':');
 103
 104   if (t == NULL) return Y4M_ERR_RANGE;
 105   r->n = atoi(s);
 106   r->d = atoi(t+1);
 107   if (r->d < 0) return Y4M_ERR_RANGE;
 108   /* 0:0 == unknown, so that is ok, otherwise zero denominator is bad */
 109   if ((r->d == 0) && (r->n != 0)) return Y4M_ERR_RANGE;
 110   y4m_ratio_reduce(r);
 111   return Y4M_OK;
 112 }
 113