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media-timer.cc

/*
 * Copyright (c) 1995 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the Computer Systems
 *    Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
static const char rcsid[] =
    "@(#) $Header: media-timer.cc,v 1.7 96/03/23 04:07:47 van Exp $ (LBL)";

#include "config.h"
#include <math.h>
#include "sys-time.h"
#include "media-timer.h"

MediaTimer* MediaTimer::instance_;

MediaTimer::MediaTimer()
{
      instance_ = this;
      offset_ = random();
}

MediaTimer::~MediaTimer()
{
      instance_ = 0;
}

/*
 * Default media timestamp -- convert unix system clock
 * into a 90Khz timestamp.  Grabbers override this virtual
 * method if they can provide their own time base.
 *
 * XXX
 * We save the corresponding unix time stamp to handle the
 * unix_ts() call the transmitter will make to get the correspondence
 * between the media timestamp & unix time.
 */
u_int32_t MediaTimer::media_ts()
{
      timeval tv;
      ::gettimeofday(&tv, 0);
      u_int32_t u = tv.tv_usec;
      u = (u << 3) + u; /* x 9 */
      /* sec * 90Khz + (usec * 90Khz) / 1e6 */
      u = tv.tv_sec * 90000 + (u / 100);
      return (u + offset_);
}

/*
 * compute media time corresponding to the current unix time.
 * in this generic routine, this is the same as media_ts() but,
 * if a grabber has hardware or kernel timestamping, this routine
 * must compute the correspondence between the hardware timestamp
 * and the unix clock and appropriately offset the timestamp to
 * correspond to the current clock.  (This information if vital
 * for cross-media synchronization.)
 */
u_int32_t MediaTimer::ref_ts()
{
      return (media_ts());
}

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