FFmpeg/libavcodec/mpeg4video.h

/*
 * MPEG-4 encoder/decoder internal header.
 * Copyright (c) 2000,2001 Fabrice Bellard
 * Copyright (c) 2002-2010 Michael Niedermayer <michaelni@gmx.at>
 *
 * 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
 */

#ifndef AVCODEC_MPEG4VIDEO_H
#define AVCODEC_MPEG4VIDEO_H

#include <stdint.h>

#include "mpegvideo.h"

void ff_mpeg4_clean_buffers(MpegEncContext *s);
int ff_mpeg4_get_video_packet_prefix_length(MpegEncContext *s);
void ff_mpeg4_init_direct_mv(MpegEncContext *s);

/**
 * @return the mb_type
 */
int ff_mpeg4_set_direct_mv(MpegEncContext *s, int mx, int my);

#if 0 //3IV1 is quite rare and it slows things down a tiny bit
#define IS_3IV1 s->codec_tag == AV_RL32("3IV1")
#else
#define IS_3IV1 0
#endif

/**
 * Predict the dc.
 * encoding quantized level -> quantized diff
 * decoding quantized diff -> quantized level
 * @param n block index (0-3 are luma, 4-5 are chroma)
 * @param dir_ptr pointer to an integer where the prediction direction will be stored
 */
static inline int ff_mpeg4_pred_dc(MpegEncContext *s, int n, int level,
                                   int *dir_ptr, int encoding)
{
    int a, b, c, wrap, pred, scale, ret;
    int16_t *dc_val;

    /* find prediction */
    if (n < 4)
        scale = s->y_dc_scale;
    else
        scale = s->c_dc_scale;
    if (IS_3IV1)
        scale = 8;

    wrap   = s->block_wrap[n];
    dc_val = s->dc_val[0] + s->block_index[n];

    /* B C
     * A X
     */
    a = dc_val[-1];
    b = dc_val[-1 - wrap];
    c = dc_val[-wrap];

    /* outside slice handling (we can't do that by memset as we need the
     * dc for error resilience) */
    if (s->first_slice_line && n != 3) {
        if (n != 2)
            b = c = 1024;
        if (n != 1 && s->mb_x == s->resync_mb_x)
            b = a = 1024;
    }
    if (s->mb_x == s->resync_mb_x && s->mb_y == s->resync_mb_y + 1) {
        if (n == 0 || n == 4 || n == 5)
            b = 1024;
    }

    if (abs(a - b) < abs(b - c)) {
        pred     = c;
        *dir_ptr = 1; /* top */
    } else {
        pred     = a;
        *dir_ptr = 0; /* left */
    }
    /* we assume pred is positive */
    pred = FASTDIV((pred + (scale >> 1)), scale);

    if (encoding) {
        ret = level - pred;
    } else {
        level += pred;
        ret    = level;
    }
    level *= scale;
    if (level & (~2047)) {
        if (!s->encoding && (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_AGGRESSIVE))) {
            if (level < 0) {
                av_log(s->avctx, AV_LOG_ERROR,
                       "dc<0 at %dx%d\n", s->mb_x, s->mb_y);
                return AVERROR_INVALIDDATA;
            }
            if (level > 2048 + scale) {
                av_log(s->avctx, AV_LOG_ERROR,
                       "dc overflow at %dx%d\n", s->mb_x, s->mb_y);
                return AVERROR_INVALIDDATA;
            }
        }
        if (level < 0)
            level = 0;
        else if (!(s->workaround_bugs & FF_BUG_DC_CLIP))
            level = 2047;
    }
    dc_val[0] = level;

    return ret;
}

#endif /* AVCODEC_MPEG4VIDEO_H */