FFmpeg/libavcodec/huffyuvencdsp.c

/*
 * 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 "libavutil/attributes.h"
#include "huffyuvencdsp.h"
#include "mathops.h"

// 0x00010001 or 0x0001000100010001 or whatever, depending on the cpu's native arithmetic size
#define pw_1 (ULONG_MAX / UINT16_MAX)

static void diff_int16_c(uint16_t *dst, const uint16_t *src1, const uint16_t *src2, unsigned mask, int w){
    long i;
#if !HAVE_FAST_UNALIGNED
    if((long)src2 & (sizeof(long)-1)){
        for(i=0; i+3<w; i+=4){
            dst[i+0] = (src1[i+0]-src2[i+0]) & mask;
            dst[i+1] = (src1[i+1]-src2[i+1]) & mask;
            dst[i+2] = (src1[i+2]-src2[i+2]) & mask;
            dst[i+3] = (src1[i+3]-src2[i+3]) & mask;
        }
    }else
#endif
    {
        unsigned long pw_lsb = (mask >> 1) * pw_1;
        unsigned long pw_msb = pw_lsb +  pw_1;

        for (i = 0; i <= w - (int)sizeof(long)/2; i += sizeof(long)/2) {
            long a = *(long*)(src1+i);
            long b = *(long*)(src2+i);
            *(long*)(dst+i) = ((a|pw_msb) - (b&pw_lsb)) ^ ((a^b^pw_msb)&pw_msb);
        }
    }
    for (; i<w; i++)
        dst[i] = (src1[i] - src2[i]) & mask;
}

static void sub_hfyu_median_pred_int16_c(uint16_t *dst, const uint16_t *src1, const uint16_t *src2, unsigned mask, int w, int *left, int *left_top){
    int i;
    uint16_t l, lt;

    l  = *left;
    lt = *left_top;

    for(i=0; i<w; i++){
        const int pred = mid_pred(l, src1[i], (l + src1[i] - lt) & mask);
        lt = src1[i];
        l  = src2[i];
        dst[i] = (l - pred) & mask;
    }

    *left     = l;
    *left_top = lt;
}

av_cold void ff_huffyuvencdsp_init(HuffYUVEncDSPContext *c, enum AVPixelFormat pix_fmt)
{
    c->diff_int16           = diff_int16_c;
    c->sub_hfyu_median_pred_int16 = sub_hfyu_median_pred_int16_c;

#if ARCH_X86
    ff_huffyuvencdsp_init_x86(c, pix_fmt);
#endif
}