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 = 16 + 2 * state->bpp - state->qbpp;
    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);
}