jpegls.h

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/*
 * JPEG-LS common code
 * Copyright (c) 2003 Michael Niedermayer
 * Copyright (c) 2006 Konstantin Shishkov
 *
 * 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
 */

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

#ifndef AVCODEC_JPEGLS_H
#define AVCODEC_JPEGLS_H

#include "libavutil/common.h"
#include "avcodec.h"
#include "internal.h"

typedef struct JpeglsContext {
    AVCodecContext *avctx;
} JpeglsContext;

typedef struct JLSState {
    int T1, T2, T3;
    int A[367], B[367], C[365], N[367];
    int limit, reset, bpp, qbpp, maxval, range;
    int near, twonear;
    int run_index[4];
} JLSState;

/**
 * Calculate initial JPEG-LS parameters
 */
void ff_jpegls_init_state(JLSState *state);

/**
 * Calculate quantized gradient value, used for context determination
 */
static inline int ff_jpegls_quantize(JLSState *s, int v)
{
    if (v == 0)
        return 0;
    if (v < 0) {
        if (v <= -s->T3)
            return -4;
        if (v <= -s->T2)
            return -3;
        if (v <= -s->T1)
            return -2;
        if (v < -s->near)
            return -1;
        return 0;
    } else {
        if (v <= s->near)
            return 0;
        if (v < s->T1)
            return 1;
        if (v < s->T2)
            return 2;
        if (v < s->T3)
            return 3;
        return 4;
    }
}

/**
 * Calculate JPEG-LS codec values
 */
void ff_jpegls_reset_coding_parameters(JLSState *s, int reset_all);

static inline void ff_jpegls_downscale_state(JLSState *state, int Q)
{
    if (state->N[Q] == state->reset) {
        state->A[Q] >>= 1;
        state->B[Q] >>= 1;
        state->N[Q] >>= 1;
    }
    state->N[Q]++;
}

static inline int ff_jpegls_update_state_regular(JLSState *state,
                                                 int Q, int err)
{
    if(FFABS(err) > 0xFFFF)
        return -0x10000;
    state->A[Q] += FFABS(err);
    err         *= state->twonear;
    state->B[Q] += err;

    ff_jpegls_downscale_state(state, Q);

    if (state->B[Q] <= -state->N[Q]) {
        state->B[Q] = FFMAX(state->B[Q] + state->N[Q], 1 - state->N[Q]);
        if (state->C[Q] > -128)
            state->C[Q]--;
    } else if (state->B[Q] > 0) {
        state->B[Q] = FFMIN(state->B[Q] - state->N[Q], 0);
        if (state->C[Q] < 127)
            state->C[Q]++;
    }

    return err;
}

#define R(a, i)    (bits == 8 ?  ((uint8_t *)(a))[i]      :  ((uint16_t *)(a))[i])
#define W(a, i, v) (bits == 8 ? (((uint8_t *)(a))[i] = v) : (((uint16_t *)(a))[i] = v))

#endif /* AVCODEC_JPEGLS_H */