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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* $URL$
* $Id$
*
*/
#include "sound/timestamp.h"
namespace Audio {
static uint gcd(uint a, uint b) {
while (a > 0) {
int tmp = a;
a = b % a;
b = tmp;
}
return b;
}
Timestamp::Timestamp(uint32 m, int framerate) :
_msecs(m), _framerate(framerate), _numberOfFrames(0) {
assert(_framerate > 0);
}
Timestamp Timestamp::convertToFramerate(int newFramerate) const {
Timestamp ts(*this);
if (ts._framerate != newFramerate) {
ts._framerate = newFramerate;
const uint g = gcd(_framerate, ts._framerate);
const uint p = _framerate / g;
const uint q = ts._framerate / g;
// Convert the frame offset to the new framerate.
// We round to the nearest (as opposed to always
// rounding down), to minimize rounding errors during
// round trip conversions.
ts._numberOfFrames = (ts._numberOfFrames * q + p/2) / p;
ts._msecs += (ts._numberOfFrames / ts._framerate) * 1000;
ts._numberOfFrames %= ts._framerate;
}
return ts;
}
bool Timestamp::operator==(const Timestamp &ts) const {
// TODO: Improve this
return (ts.msecs() == msecs()) && !frameDiff(ts);
}
bool Timestamp::operator!=(const Timestamp &ts) const {
return !(*this == ts);
}
Timestamp Timestamp::addFrames(int frames) const {
Timestamp ts(*this);
ts._numberOfFrames += frames;
if (ts._numberOfFrames < 0) {
int secsub = 1 + (-ts._numberOfFrames / ts._framerate);
ts._numberOfFrames += ts._framerate * secsub;
ts._msecs -= secsub * 1000;
}
ts._msecs += (ts._numberOfFrames / ts._framerate) * 1000;
ts._numberOfFrames %= ts._framerate;
return ts;
}
Timestamp Timestamp::addMsecs(int ms) const {
Timestamp ts(*this);
ts._msecs += ms;
return ts;
}
int Timestamp::frameDiff(const Timestamp &ts) const {
int delta = 0;
if (_msecs != ts._msecs)
delta = (long(_msecs) - long(ts._msecs)) * _framerate / 1000;
delta += _numberOfFrames;
if (_framerate == ts._framerate) {
delta -= ts._numberOfFrames;
} else {
// We need to multiply by the quotient of the two framerates.
// We cancel the GCD in this fraction to reduce the risk of
// overflows.
const uint g = gcd(_framerate, ts._framerate);
const uint p = _framerate / g;
const uint q = ts._framerate / g;
delta -= (ts._numberOfFrames * p + q/2) / q;
}
return delta;
}
int Timestamp::msecsDiff(const Timestamp &ts) const {
return long(msecs()) - long(ts.msecs());
}
uint32 Timestamp::msecs() const {
return _msecs + _numberOfFrames * 1000L / _framerate;
}
} // End of namespace Audio
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