chrono.h

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/*****************************************************************************
 * chrono.h: vout chrono
 *****************************************************************************
 * Copyright (C) 2009-2010 Laurent Aimar
 *
 * Authors: Laurent Aimar <fenrir _AT_ videolan _DOT_ org>
 *
 * This program 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.
 *
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser 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.
 *****************************************************************************/
 
#ifndef LIBVLC_VOUT_CHRONO_H
#define LIBVLC_VOUT_CHRONO_H
 
#include <assert.h>
 
typedef struct {
    int     shift;
    vlc_tick_t avg;
    unsigned avg_count;
 
    int     shift_mad;
    vlc_tick_t mad; /* mean absolute deviation */
    unsigned mad_count;
 
    vlc_tick_t start;
} vout_chrono_t;
 
static inline void vout_chrono_Init(vout_chrono_t *chrono, int shift, vlc_tick_t avg_initial)
{
    chrono->avg_count   = 0;
    chrono->mad_count   = 0;
 
    chrono->shift       = shift;
    chrono->avg         = avg_initial;
 
    chrono->shift_mad   = shift+1;
    chrono->mad         = 0;
 
    chrono->start = VLC_TICK_INVALID;
}
 
static inline void vout_chrono_Start(vout_chrono_t *chrono)
{
    chrono->start = vlc_tick_now();
}
 
static inline vlc_tick_t vout_chrono_GetHigh(vout_chrono_t *chrono)
{
    return chrono->avg + 2 * chrono->mad;
}
 
static inline vlc_tick_t vout_chrono_GetLow(vout_chrono_t *chrono)
{
    return __MAX(chrono->avg - 2 * chrono->mad, 0);
}
 
static inline void vout_chrono_Stop(vout_chrono_t *chrono)
{
    assert(chrono->start != VLC_TICK_INVALID);
 
    const vlc_tick_t duration = vlc_tick_now() - chrono->start;
 
    if (chrono->avg_count == 0)
    {
        /* Overwrite the arbitrary initial values with the real first sample */
        chrono->avg = duration;
        chrono->avg_count = 1;
    }
    else
    {
        /* Update average only if the current point is 'valid' */
        if( duration < vout_chrono_GetHigh( chrono ) )
        {
            if (chrono->avg_count < (1u << chrono->shift))
                ++chrono->avg_count;
            chrono->avg = ((chrono->avg_count - 1) * chrono->avg + duration) / chrono->avg_count;
        }
 
        const vlc_tick_t abs_diff = llabs( duration - chrono->avg );
 
        /* Always update the mean absolute deviation */
        if (chrono->mad_count < (1u << chrono->shift_mad))
            ++chrono->mad_count;
        chrono->mad = ((chrono->mad_count - 1) * chrono->mad + abs_diff) / chrono->mad_count;
    }
 
    /* For assert */
    chrono->start = VLC_TICK_INVALID;
}
 
#endif