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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.
*
* $URL$
* $Id$
*
*/
#ifndef SOUND_TIMESTAMP_H
#define SOUND_TIMESTAMP_H
#include "common/scummsys.h"
namespace Audio {
/**
* Timestamps allow measuring times with a sub-millisecond granularity,
* and without rounding losses. This is achieved by measuring frames
* instead of milliseconds: Specify an initial time in milliseconds
* plus framerate (in frames per second).
*/
class Timestamp {
protected:
/**
* The seconds part of this timestamp.
* The total time in seconds represented by this timestamp can be
* computed as follows:
* _secs + (double)_numberOfFrames / _framerate
*/
uint _secs;
/**
* The number of frames which together with _secs encodes
* the timestamp. The total number of frames represented
* by this timestamp is computed as follows:
* _numberOfFrames + _secs * _framerate
*/
int _numberOfFrames;
/**
* The internal framerate, i.e. the number of frames per second.
* This is computed as the least common multiple of the framerate
* specified by the client code, and 1000.
* This way, we ensure that we can store both frames and
* milliseconds without any rounding losses.
*/
int _framerate;
/**
* Factor by which the original framerate specified by the client
* code was multipled to obtain the internal _framerate value.
*/
int _framerateFactor;
public:
/**
* Set up a timestamp with a given time and framerate.
* @param msecs starting time in milliseconds
* @param framerate number of frames per second (must be > 0)
*/
Timestamp(uint32 msecs, int framerate);
/**
* Set up a timestamp with a given time, frames and framerate.
* @param secs starting time in seconds
* @param frames starting frames
* @param framerate number of frames per second (must be > 0)
*/
Timestamp(uint secs, int frames, int framerate);
/**
* Return a timestamp which represents as closely as possible
* the point in time describes by this timestamp, but with
* a different framerate.
*/
Timestamp convertToFramerate(int newFramerate) const;
/**
* Check whether to timestamps describe the exact same moment
* in time. This means that two timestamps can compare
* as equal even if they use different framerates.
*/
bool operator==(const Timestamp &ts) const;
bool operator!=(const Timestamp &ts) const;
bool operator<(const Timestamp &ts) const;
bool operator<=(const Timestamp &ts) const;
bool operator>(const Timestamp &ts) const;
bool operator>=(const Timestamp &ts) const;
/**
* Returns a new timestamp, which corresponds to the time encoded
* by this timestamp with the given number of frames added.
* @param frames number of frames to add
*/
Timestamp addFrames(int frames) const;
/**
* Returns a new timestamp, which corresponds to the time encoded
* by this timestamp with the given number of milliseconds added.
* @param msecs number of milliseconds to add
*/
Timestamp addMsecs(int msecs) const;
/**
* Computes the number of frames between this timestamp and ts.
* The frames are with respect to the framerate used by this
* Timestamp (which may differ from the framerate used by ts).
*/
int frameDiff(const Timestamp &ts) const;
/** Computes the number off milliseconds between this timestamp and ts. */
int msecsDiff(const Timestamp &ts) const;
/**
* Return the time in milliseconds described by this timestamp,
* rounded down.
*/
uint32 msecs() const;
/**
* Return the time in seconds described by this timestamp,
* rounded down.
*/
inline uint32 secs() const {
return _secs;
}
/**
* Return the time in frames described by this timestamp.
*/
inline int totalNumberOfFrames() const {
return _numberOfFrames / _framerateFactor + _secs * (_framerate / _framerateFactor);
}
/**
* A timestamp consists of a number of seconds, plus a number
* of frames, the latter describing a fraction of a second.
* This method returns the latter number.
*/
inline int numberOfFrames() const {
return _numberOfFrames / _framerateFactor;
}
/** Return the framerate used by this timestamp. */
inline int framerate() const { return _framerate / _framerateFactor; }
protected:
int cmp(const Timestamp &ts) const;
};
} // End of namespace Audio
#endif
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