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FFmpeg/libavutil/time.c
Olivier Langlois 0eec06ed87 lavu: add av_gettime_relative()
These functions are using the POSIX clock_gettime() function with the
CLOCK_MONOTONIC clock id. If these are not present on the targeted
platform, the new functions will fallback on using the original realtime functions
av_gettime() and av_usleep().

Monotonic support can be added on other platforms with their
equivalent native system API eventually if possible.

Whenever time is requested to measure relative time, the monotonic clock,
when available, is superior to the system realtime clock because it is
not affected by discontinuous jumps in the system time

In a future step, offering the flexibility to let the user choose between
rt and monotonic clock for avdevices packets will be investigated.

It is very easy to experience the issues that this patch attempt to address
by rewinding back in the past the system time while ffmpeg is running.

this is breaking the ffmpeg report printing (ffmepg.c:print_report()) and
the the rate emulator functionality (-re) without the patch.

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
2014-05-17 15:28:03 +02:00

91 lines
2.1 KiB
C

/*
* Copyright (c) 2000-2003 Fabrice Bellard
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include <stddef.h>
#include <stdint.h>
#include <time.h>
#if HAVE_GETTIMEOFDAY
#include <sys/time.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_WINDOWS_H
#include <windows.h>
#endif
#include "time.h"
#include "error.h"
int64_t av_gettime(void)
{
#if HAVE_GETTIMEOFDAY
struct timeval tv;
gettimeofday(&tv, NULL);
return (int64_t)tv.tv_sec * 1000000 + tv.tv_usec;
#elif HAVE_GETSYSTEMTIMEASFILETIME
FILETIME ft;
int64_t t;
GetSystemTimeAsFileTime(&ft);
t = (int64_t)ft.dwHighDateTime << 32 | ft.dwLowDateTime;
return t / 10 - 11644473600000000; /* Jan 1, 1601 */
#else
return -1;
#endif
}
int64_t av_gettime_relative(void)
{
#if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return (int64_t)ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
#else
return av_gettime();
#endif
}
int av_gettime_relative_is_monotonic(void)
{
#if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
return 1;
#else
return 0;
#endif
}
int av_usleep(unsigned usec)
{
#if HAVE_NANOSLEEP
struct timespec ts = { usec / 1000000, usec % 1000000 * 1000 };
while (nanosleep(&ts, &ts) < 0 && errno == EINTR);
return 0;
#elif HAVE_USLEEP
return usleep(usec);
#elif HAVE_SLEEP
Sleep(usec / 1000);
return 0;
#else
return AVERROR(ENOSYS);
#endif
}