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/*
* yuv4mpeg_ratio.c: Functions for dealing with y4m_ratio_t datatype.
*
* Copyright (C) 2001 Matthew J. Marjanovic <maddog@mir.com>
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
*/
#include <config.h>
#include <string.h>
#include "yuv4mpeg.h"
#include "yuv4mpeg_intern.h"
/* useful list of standard framerates */
const y4m_ratio_t y4m_fps_UNKNOWN = Y4M_FPS_UNKNOWN;
const y4m_ratio_t y4m_fps_NTSC_FILM = Y4M_FPS_NTSC_FILM;
const y4m_ratio_t y4m_fps_FILM = Y4M_FPS_FILM;
const y4m_ratio_t y4m_fps_PAL = Y4M_FPS_PAL;
const y4m_ratio_t y4m_fps_NTSC = Y4M_FPS_NTSC;
const y4m_ratio_t y4m_fps_30 = Y4M_FPS_30;
const y4m_ratio_t y4m_fps_PAL_FIELD = Y4M_FPS_PAL_FIELD;
const y4m_ratio_t y4m_fps_NTSC_FIELD = Y4M_FPS_NTSC_FIELD;
const y4m_ratio_t y4m_fps_60 = Y4M_FPS_60;
/* useful list of standard sample aspect ratios */
const y4m_ratio_t y4m_sar_UNKNOWN = Y4M_SAR_UNKNOWN;
const y4m_ratio_t y4m_sar_SQUARE = Y4M_SAR_SQUARE;
const y4m_ratio_t y4m_sar_SQR_ANA_16_9 = Y4M_SAR_SQR_ANA_16_9;
const y4m_ratio_t y4m_sar_NTSC_CCIR601 = Y4M_SAR_NTSC_CCIR601;
const y4m_ratio_t y4m_sar_NTSC_16_9 = Y4M_SAR_NTSC_16_9;
const y4m_ratio_t y4m_sar_NTSC_SVCD_4_3 = Y4M_SAR_NTSC_SVCD_4_3;
const y4m_ratio_t y4m_sar_NTSC_SVCD_16_9 = Y4M_SAR_NTSC_SVCD_16_9;
const y4m_ratio_t y4m_sar_PAL_CCIR601 = Y4M_SAR_PAL_CCIR601;
const y4m_ratio_t y4m_sar_PAL_16_9 = Y4M_SAR_PAL_16_9;
const y4m_ratio_t y4m_sar_PAL_SVCD_4_3 = Y4M_SAR_PAL_SVCD_4_3;
const y4m_ratio_t y4m_sar_PAL_SVCD_16_9 = Y4M_SAR_PAL_SVCD_16_9;
/* useful list of standard display aspect ratios */
const y4m_ratio_t y4m_dar_UNKNOWN = Y4M_DAR_UNKNOWN;
const y4m_ratio_t y4m_dar_4_3 = Y4M_DAR_4_3;
const y4m_ratio_t y4m_dar_16_9 = Y4M_DAR_16_9;
const y4m_ratio_t y4m_dar_221_100 = Y4M_DAR_221_100;
/*
* Euler's algorithm for greatest common divisor
*/
static int gcd(int a, int b)
{
a = (a >= 0) ? a : -a;
b = (b >= 0) ? b : -b;
while (b > 0) {
int x = b;
b = a % b;
a = x;
}
return a;
}
/*************************************************************************
*
* Remove common factors from a ratio
*
*************************************************************************/
void y4m_ratio_reduce(y4m_ratio_t *r)
{
int d;
if ((r->n == 0) && (r->d == 0)) return; /* "unknown" */
d = gcd(r->n, r->d);
r->n /= d;
r->d /= d;
}
/*************************************************************************
*
* Parse "nnn:ddd" into a ratio
*
* returns: Y4M_OK - success
* Y4M_ERR_RANGE - range error
*
*************************************************************************/
int y4m_parse_ratio(y4m_ratio_t *r, const char *s)
{
char *t = strchr(s, ':');
if (t == NULL) return Y4M_ERR_RANGE;
r->n = atoi(s);
r->d = atoi(t+1);
if (r->d < 0) return Y4M_ERR_RANGE;
/* 0:0 == unknown, so that is ok, otherwise zero denominator is bad */
if ((r->d == 0) && (r->n != 0)) return Y4M_ERR_RANGE;
y4m_ratio_reduce(r);
return Y4M_OK;
}
/*************************************************************************
*
* Guess the true SAR (sample aspect ratio) from a list of commonly
* encountered values, given the "suggested" display aspect ratio, and
* the true frame width and height.
*
* Returns y4m_sar_UNKNOWN if no match is found.
*
*************************************************************************/
/* this is big enough to accommodate the difference between 720 and 704 */
#define GUESS_ASPECT_TOLERANCE 0.03
y4m_ratio_t y4m_guess_sar(int width, int height, y4m_ratio_t dar)
{
int i;
double implicit_sar = (double)(dar.n * height) / (double)(dar.d * width);
const y4m_ratio_t *sarray[] =
{
&y4m_sar_SQUARE,
&y4m_sar_NTSC_CCIR601,
&y4m_sar_NTSC_16_9,
&y4m_sar_NTSC_SVCD_4_3,
&y4m_sar_NTSC_SVCD_16_9,
&y4m_sar_PAL_CCIR601,
&y4m_sar_PAL_16_9,
&y4m_sar_PAL_SVCD_4_3,
&y4m_sar_PAL_SVCD_16_9,
&y4m_sar_UNKNOWN
};
for (i = 0; !(Y4M_RATIO_EQL(*(sarray[i]),y4m_sar_UNKNOWN)); i++) {
double ratio = implicit_sar / Y4M_RATIO_DBL(*(sarray[i]));
if ( (ratio > (1.0 - GUESS_ASPECT_TOLERANCE)) &&
(ratio < (1.0 + GUESS_ASPECT_TOLERANCE)) )
return *(sarray[i]);
}
return y4m_sar_UNKNOWN;
}
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