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ffmpeg / libavcodec / jpegls.c @ 2912e87a

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/*
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 * JPEG-LS common code
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 * Copyright (c) 2003 Michael Niedermayer
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 * Copyright (c) 2006 Konstantin Shishkov
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file
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 * JPEG-LS common code.
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 */
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#include "jpegls.h"
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void ff_jpegls_init_state(JLSState *state){
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    int i;
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    state->twonear = state->near * 2 + 1;
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    state->range = ((state->maxval + state->twonear - 1) / state->twonear) + 1;
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    // QBPP = ceil(log2(RANGE))
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    for(state->qbpp = 0; (1 << state->qbpp) < state->range; state->qbpp++);
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    if(state->bpp < 8)
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        state->limit = 16 + 2 * state->bpp - state->qbpp;
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    else
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        state->limit = (4 * state->bpp) - state->qbpp;
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    for(i = 0; i < 367; i++) {
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        state->A[i] = FFMAX((state->range + 32) >> 6, 2);
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        state->N[i] = 1;
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    }
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}
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/**
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 * Custom value clipping function used in T1, T2, T3 calculation
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 */
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static inline int iso_clip(int v, int vmin, int vmax){
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    if(v > vmax || v < vmin) return vmin;
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    else                     return v;
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}
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void ff_jpegls_reset_coding_parameters(JLSState *s, int reset_all){
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    const int basic_t1= 3;
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    const int basic_t2= 7;
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    const int basic_t3= 21;
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    int factor;
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    if(s->maxval==0 || reset_all) s->maxval= (1 << s->bpp) - 1;
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    if(s->maxval >=128){
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        factor= (FFMIN(s->maxval, 4095) + 128)>>8;
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        if(s->T1==0     || reset_all)
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            s->T1= iso_clip(factor*(basic_t1-2) + 2 + 3*s->near, s->near+1, s->maxval);
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        if(s->T2==0     || reset_all)
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            s->T2= iso_clip(factor*(basic_t2-3) + 3 + 5*s->near, s->T1, s->maxval);
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        if(s->T3==0     || reset_all)
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            s->T3= iso_clip(factor*(basic_t3-4) + 4 + 7*s->near, s->T2, s->maxval);
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    }else{
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        factor= 256 / (s->maxval + 1);
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        if(s->T1==0     || reset_all)
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            s->T1= iso_clip(FFMAX(2, basic_t1/factor + 3*s->near), s->near+1, s->maxval);
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        if(s->T2==0     || reset_all)
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            s->T2= iso_clip(FFMAX(3, basic_t2/factor + 5*s->near), s->T1, s->maxval);
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        if(s->T3==0     || reset_all)
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            s->T3= iso_clip(FFMAX(4, basic_t3/factor + 7*s->near), s->T2, s->maxval);
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    }
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    if(s->reset==0  || reset_all) s->reset= 64;
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//    av_log(NULL, AV_LOG_DEBUG, "[JPEG-LS RESET] T=%i,%i,%i\n", s->T1, s->T2, s->T3);
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}