FFmpeg/libavcodec/jpegls.c

/*
 * JPEG-LS common code
 * Copyright (c) 2003 Michael Niedermayer
 * Copyright (c) 2006 Konstantin Shishkov
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * JPEG-LS common code.
 */

#include "jpegls.h"

void ff_jpegls_init_state(JLSState *state)
{
    int i;

    state->twonear = state->near * 2 + 1;
    state->range   = (state->maxval + state->twonear - 1) / state->twonear + 1;

    // QBPP = ceil(log2(RANGE))
    for (state->qbpp = 0; (1 << state->qbpp) < state->range; state->qbpp++)
        ;

    if (state->bpp < 8)
        state->limit = 2 * state->bpp - state->qbpp + 16;
    else
        state->limit = 4 * state->bpp - state->qbpp;

    for (i = 0; i < 367; i++) {
        state->A[i] = FFMAX(state->range + 32 >> 6, 2);
        state->N[i] = 1;
    }
}

/**
 * Custom value clipping function used in T1, T2, T3 calculation
 */
static inline int iso_clip(int v, int vmin, int vmax)
{
    if (v > vmax || v < vmin)
        return vmin;
    else
        return v;
}

void ff_jpegls_reset_coding_parameters(JLSState *s, int reset_all)
{
    const int basic_t1 = 3;
    const int basic_t2 = 7;
    const int basic_t3 = 21;
    int factor;

    if (s->maxval == 0 || reset_all)
        s->maxval = (1 << s->bpp) - 1;

    if (s->maxval >= 128) {
        factor = FFMIN(s->maxval, 4095) + 128 >> 8;

        if (s->T1 == 0 || reset_all)
            s->T1 = iso_clip(factor * (basic_t1 - 2) + 2 + 3 * s->near,
                             s->near + 1, s->maxval);
        if (s->T2 == 0 || reset_all)
            s->T2 = iso_clip(factor * (basic_t2 - 3) + 3 + 5 * s->near,
                             s->T1, s->maxval);
        if (s->T3 == 0 || reset_all)
            s->T3 = iso_clip(factor * (basic_t3 - 4) + 4 + 7 * s->near,
                             s->T2, s->maxval);
    } else {
        factor = 256 / (s->maxval + 1);

        if (s->T1 == 0 || reset_all)
            s->T1 = iso_clip(FFMAX(2, basic_t1 / factor + 3 * s->near),
                             s->near + 1, s->maxval);
        if (s->T2 == 0 || reset_all)
            s->T2 = iso_clip(FFMAX(3, basic_t2 / factor + 5 * s->near),
                             s->T1, s->maxval);
        if (s->T3 == 0 || reset_all)
            s->T3 = iso_clip(FFMAX(4, basic_t3 / factor + 7 * s->near),
                             s->T2, s->maxval);
    }

    if (s->reset == 0 || reset_all)
        s->reset = 64;
    av_dlog(NULL, "[JPEG-LS RESET] T=%i,%i,%i\n", s->T1, s->T2, s->T3);
}