gstreamer/gst-libs/gst/video/video.c
Jan Schmidt c98f051548 video: Add gst_video_guess_framerate() function
Takes a nominal frame duration and returns a standard
FPS if it matches closely enough (< 0.1%), or else
calculates a framerate that'll do.
2014-08-15 01:08:22 +10:00

209 lines
5.9 KiB
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., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, 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.
*/
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;
}
}
/**
* gst_video_guess_framerate:
* @duration: Nominal duration of one frame
* @dest_n: (out) (allow-none): Numerator of the calculated framerate
* @dest_d: (out) (allow-none): Denominator of the calculated framerate
*
* Given the nominal duration of one video frame,
* this function will check some standard framerates for
* a close match (within 0.1%) and return one if possible,
*
* It will calculate an arbitrary framerate if no close
* match was found, and return %FALSE.
*
* It returns %FALSE if a duration of 0 is passed.
*
* Returns: %TRUE if a close "standard" framerate was
* recognised, and %FALSE otherwise.
*
* Since: 1.6
*/
gboolean
gst_video_guess_framerate (GstClockTime duration, gint * dest_n, gint * dest_d)
{
const int common_den[] = { 1, 2, 3, 4, 1001 };
int best_n, best_d, gcd;
guint64 best_error = G_MAXUINT64;
guint64 a;
int i;
if (G_UNLIKELY (duration == 0))
return FALSE;
/* Use a limited precision conversion by default for more sensible results,
* unless the frame duration is absurdly small (high speed cameras?) */
if (duration > 100000) {
best_n = 10000;
best_d = duration / 100000;
} else {
best_n = GST_SECOND;
best_d = duration;
}
for (i = 0; i < G_N_ELEMENTS (common_den); i++) {
gint d = common_den[i];
gint n = gst_util_uint64_scale_round (d, GST_SECOND, duration);
/* For NTSC framerates, round to the nearest 1000 fps */
if (d == 1001) {
n += 500;
n -= (n % 1000);
}
if (n > 0) {
/* See what duration the given framerate should be */
a = gst_util_uint64_scale_int (GST_SECOND, d, n);
/* Compute absolute error */
a = (a < duration) ? (duration - a) : (a - duration);
if (a < 2) {
/* Really precise - take this option */
if (dest_n)
*dest_n = n;
if (dest_d)
*dest_d = d;
return TRUE;
}
/* If within 0.1%, remember this denominator */
if (a * 1000 < duration && a < best_error) {
best_error = a;
best_n = n;
best_d = d;
}
}
}
/* set results */
gcd = gst_util_greatest_common_divisor (best_n, best_d);
if (gcd) {
best_n /= gcd;
best_d /= gcd;
}
if (dest_n)
*dest_n = best_n;
if (dest_d)
*dest_d = best_d;
return (best_error != G_MAXUINT64);
}
/**
* gst_video_alignment_reset:
* @align: a #GstVideoAlignment
*
* Set @align to its default values with no padding and no alignment.
*/
void
gst_video_alignment_reset (GstVideoAlignment * align)
{
gint i;
g_return_if_fail (align != NULL);
align->padding_top = 0;
align->padding_bottom = 0;
align->padding_left = 0;
align->padding_right = 0;
for (i = 0; i < GST_VIDEO_MAX_PLANES; i++)
align->stride_align[i] = 0;
}