libavcodec/mpeg4video.c

/*
 * MPEG-4 decoder / encoder common code
 * 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
 */

#include "mpegutils.h"
#include "mpegvideo.h"
#include "mpeg4video.h"
#include "mpeg4data.h"

int ff_mpeg4_get_video_packet_prefix_length(enum AVPictureType pict_type,
                                            int f_code, int b_code)
{
    switch (pict_type) {
    case AV_PICTURE_TYPE_I:
        return 16;
    case AV_PICTURE_TYPE_P:
    case AV_PICTURE_TYPE_S:
        return f_code + 15;
    case AV_PICTURE_TYPE_B:
        return FFMAX3(f_code, b_code, 2) + 15;
    default:
        return -1;
    }
}

void ff_mpeg4_clean_buffers(MpegEncContext *s)
{
    const int mb_height = s->mb_height;
    int c_wrap, l_wrap, l_xy;

    l_wrap = s->b8_stride;
    l_xy   = (2 * s->mb_y - 1) * l_wrap + s->mb_x * 2 - 1;
    c_wrap = s->mb_stride;
    int u_xy = 2 * mb_height * l_wrap + s->mb_y * c_wrap + s->mb_x - 1;
    int v_xy = u_xy + c_wrap * (mb_height + 1);
    int16_t (*ac_val)[16] = s->ac_val;

    /* clean AC */
    memset(ac_val + l_xy, 0, (l_wrap * 2 + 1) * sizeof(*ac_val));
    memset(ac_val + u_xy, 0, (c_wrap     + 1) * sizeof(*ac_val));
    memset(ac_val + v_xy, 0, (c_wrap     + 1) * sizeof(*ac_val));

    /* clean MV */
    // we can't clear the MVs as they might be needed by a B-frame
    s->last_mv[0][0][0] =
    s->last_mv[0][0][1] =
    s->last_mv[1][0][0] =
    s->last_mv[1][0][1] = 0;
}

#define tab_size ((signed)FF_ARRAY_ELEMS(s->direct_scale_mv[0]))
#define tab_bias (tab_size / 2)

// used by MPEG-4 and rv10 decoder
void ff_mpeg4_init_direct_mv(MpegEncContext *s)
{
    int i;
    for (i = 0; i < tab_size; i++) {
        s->direct_scale_mv[0][i] = (i - tab_bias) * s->pb_time / s->pp_time;
        s->direct_scale_mv[1][i] = (i - tab_bias) * (s->pb_time - s->pp_time) /
                                   s->pp_time;
    }
}

static inline void ff_mpeg4_set_one_direct_mv(MpegEncContext *s, int mx,
                                              int my, int i)
{
    int xy           = s->block_index[i];
    uint16_t time_pp = s->pp_time;
    uint16_t time_pb = s->pb_time;
    int p_mx, p_my;

    p_mx = s->next_pic.motion_val[0][xy][0];
    if ((unsigned)(p_mx + tab_bias) < tab_size) {
        s->mv[0][i][0] = s->direct_scale_mv[0][p_mx + tab_bias] + mx;
        s->mv[1][i][0] = mx ? s->mv[0][i][0] - p_mx
                            : s->direct_scale_mv[1][p_mx + tab_bias];
    } else {
        s->mv[0][i][0] = p_mx * time_pb / time_pp + mx;
        s->mv[1][i][0] = mx ? s->mv[0][i][0] - p_mx
                            : p_mx * (time_pb - time_pp) / time_pp;
    }
    p_my = s->next_pic.motion_val[0][xy][1];
    if ((unsigned)(p_my + tab_bias) < tab_size) {
        s->mv[0][i][1] = s->direct_scale_mv[0][p_my + tab_bias] + my;
        s->mv[1][i][1] = my ? s->mv[0][i][1] - p_my
                            : s->direct_scale_mv[1][p_my + tab_bias];
    } else {
        s->mv[0][i][1] = p_my * time_pb / time_pp + my;
        s->mv[1][i][1] = my ? s->mv[0][i][1] - p_my
                            : p_my * (time_pb - time_pp) / time_pp;
    }
}

#undef tab_size
#undef tab_bias

/**
 * @return the mb_type
 */
int ff_mpeg4_set_direct_mv(MpegEncContext *s, int mx, int my)
{
    const int mb_index          = s->mb_x + s->mb_y * s->mb_stride;
    const int colocated_mb_type = s->next_pic.mb_type[mb_index];
    uint16_t time_pp;
    uint16_t time_pb;
    int i;

    // FIXME avoid divides
    // try special case with shifts for 1 and 3 B-frames?

    if (IS_8X8(colocated_mb_type)) {
        s->mv_type = MV_TYPE_8X8;
        for (i = 0; i < 4; i++)
            ff_mpeg4_set_one_direct_mv(s, mx, my, i);
        return MB_TYPE_DIRECT2 | MB_TYPE_8x8 | MB_TYPE_BIDIR_MV;
    } else if (IS_INTERLACED(colocated_mb_type)) {
        s->mv_type = MV_TYPE_FIELD;
        for (i = 0; i < 2; i++) {
            int field_select = s->next_pic.ref_index[0][4 * mb_index + 2 * i];
            s->field_select[0][i] = field_select;
            s->field_select[1][i] = i;
            if (s->top_field_first) {
                time_pp = s->pp_field_time - field_select + i;
                time_pb = s->pb_field_time - field_select + i;
            } else {
                time_pp = s->pp_field_time + field_select - i;
                time_pb = s->pb_field_time + field_select - i;
            }
            s->mv[0][i][0] = s->p_field_mv_table[i][0][mb_index][0] *
                             time_pb / time_pp + mx;
            s->mv[0][i][1] = s->p_field_mv_table[i][0][mb_index][1] *
                             time_pb / time_pp + my;
            s->mv[1][i][0] = mx ? s->mv[0][i][0] -
                                  s->p_field_mv_table[i][0][mb_index][0]
                                : s->p_field_mv_table[i][0][mb_index][0] *
                                  (time_pb - time_pp) / time_pp;
            s->mv[1][i][1] = my ? s->mv[0][i][1] -
                                  s->p_field_mv_table[i][0][mb_index][1]
                                : s->p_field_mv_table[i][0][mb_index][1] *
                                  (time_pb - time_pp) / time_pp;
        }
        return MB_TYPE_DIRECT2 | MB_TYPE_16x8 |
               MB_TYPE_BIDIR_MV | MB_TYPE_INTERLACED;
    } else {
        ff_mpeg4_set_one_direct_mv(s, mx, my, 0);
        s->mv[0][1][0] =
        s->mv[0][2][0] =
        s->mv[0][3][0] = s->mv[0][0][0];
        s->mv[0][1][1] =
        s->mv[0][2][1] =
        s->mv[0][3][1] = s->mv[0][0][1];
        s->mv[1][1][0] =
        s->mv[1][2][0] =
        s->mv[1][3][0] = s->mv[1][0][0];
        s->mv[1][1][1] =
        s->mv[1][2][1] =
        s->mv[1][3][1] = s->mv[1][0][1];
        if ((s->avctx->workaround_bugs & FF_BUG_DIRECT_BLOCKSIZE) ||
            !s->quarter_sample)
            s->mv_type = MV_TYPE_16X16;
        else
            s->mv_type = MV_TYPE_8X8;
        // Note see prev line
        return MB_TYPE_DIRECT2 | MB_TYPE_16x16 | MB_TYPE_BIDIR_MV;
    }
}