gstreamer/gst-libs/gst/video/video.c

/* GStreamer
 * Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
 * Library       <2002> Ronald Bultje <rbultje@ronald.bitfreak.net>
 * Copyright (C) 2007 David A. Schleef <ds@schleef.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include <string.h>
#include <stdio.h>

#include "video.h"
#include "gstvideometa.h"

/**
 * SECTION:gstvideo
 * @short_description: Support library for video operations
 *
 * <refsect2>
 * <para>
 * This library contains some helper functions and includes the
 * videosink and videofilter base classes.
 * </para>
 * </refsect2>
 */

/**
 * gst_video_calculate_display_ratio:
 * @dar_n: Numerator of the calculated display_ratio
 * @dar_d: Denominator of the calculated display_ratio
 * @video_width: Width of the video frame in pixels
 * @video_height: Height of the video frame in pixels
 * @video_par_n: Numerator of the pixel aspect ratio of the input video.
 * @video_par_d: Denominator of the pixel aspect ratio of the input video.
 * @display_par_n: Numerator of the pixel aspect ratio of the display device
 * @display_par_d: Denominator of the pixel aspect ratio of the display device
 *
 * Given the Pixel Aspect Ratio and size of an input video frame, and the
 * pixel aspect ratio of the intended display device, calculates the actual
 * display ratio the video will be rendered with.
 *
 * Returns: A boolean indicating success and a calculated Display Ratio in the
 * dar_n and dar_d parameters.
 * The return value is FALSE in the case of integer overflow or other error.
 *
 * Since: 0.10.7
 */
gboolean
gst_video_calculate_display_ratio (guint * dar_n, guint * dar_d,
    guint video_width, guint video_height,
    guint video_par_n, guint video_par_d,
    guint display_par_n, guint display_par_d)
{
  gint num, den;
  gint tmp_n, tmp_d;

  g_return_val_if_fail (dar_n != NULL, FALSE);
  g_return_val_if_fail (dar_d != NULL, FALSE);

  /* Calculate (video_width * video_par_n * display_par_d) /
   * (video_height * video_par_d * display_par_n) */
  if (!gst_util_fraction_multiply (video_width, video_height, video_par_n,
          video_par_d, &tmp_n, &tmp_d))
    goto error_overflow;

  if (!gst_util_fraction_multiply (tmp_n, tmp_d, display_par_d, display_par_n,
          &num, &den))
    goto error_overflow;

  g_return_val_if_fail (num > 0, FALSE);
  g_return_val_if_fail (den > 0, FALSE);

  *dar_n = num;
  *dar_d = den;

  return TRUE;

  /* ERRORS */
error_overflow:
  {
    GST_WARNING ("overflow in multiply");
    return FALSE;
  }
}