FFmpeg/libavcodec/vulkan/ffv1_common.comp

/*
 * FFv1 codec
 *
 * Copyright (c) 2024 Lynne <dev@lynne.ee>
 *
 * 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
 */

struct SliceContext {
    RangeCoder c;

#if !defined(DECODE)
    PutBitContext pb; /* 8*8 bytes */
#else
    GetBitContext gb;
#endif

    ivec2 slice_dim;
    ivec2 slice_pos;
    ivec2 slice_rct_coef;
    u8vec4 quant_table_idx;
    uint context_count;

    uint hdr_len; // only used for golomb

    uint slice_coding_mode;
    bool slice_reset_contexts;
};

/* -1, { -1, 0 } */
int predict(int L, ivec2 top)
{
    return mid_pred(L, L + top[1] - top[0], top[1]);
}

/* { -2, -1 }, { -1, 0, 1 }, 0 */
int get_context(VTYPE2 cur_l, VTYPE3 top_l, TYPE top2, uint8_t quant_table_idx)
{
    const int LT = top_l[0]; /* -1 */
    const int T  = top_l[1]; /*  0 */
    const int RT = top_l[2]; /*  1 */
    const int L  = cur_l[1]; /* -1 */

    int base = quant_table[quant_table_idx][0][(L - LT) & MAX_QUANT_TABLE_MASK] +
               quant_table[quant_table_idx][1][(LT - T) & MAX_QUANT_TABLE_MASK] +
               quant_table[quant_table_idx][2][(T - RT) & MAX_QUANT_TABLE_MASK];

    if ((quant_table[quant_table_idx][3][127] == 0) &&
        (quant_table[quant_table_idx][4][127] == 0))
        return base;

    const int TT = top2;     /* -2 */
    const int LL = cur_l[0]; /* -2 */
    return base +
           quant_table[quant_table_idx][3][(LL - L) & MAX_QUANT_TABLE_MASK] +
           quant_table[quant_table_idx][4][(TT - T) & MAX_QUANT_TABLE_MASK];
}

const uint32_t log2_run[41] = {
     0,  0,  0,  0,  1,  1,  1,  1,
     2,  2,  2,  2,  3,  3,  3,  3,
     4,  4,  5,  5,  6,  6,  7,  7,
     8,  9, 10, 11, 12, 13, 14, 15,
    16, 17, 18, 19, 20, 21, 22, 23,
    24,
};

uint slice_coord(uint width, uint sx, uint num_h_slices, uint chroma_shift)
{
    uint mpw = 1 << chroma_shift;
    uint awidth = align(width, mpw);

    if ((version < 4) || ((version == 4) && (micro_version < 3)))
        return width * sx / num_h_slices;

    sx = (2 * awidth * sx + num_h_slices * mpw) / (2 * num_h_slices * mpw) * mpw;
    if (sx == awidth)
        sx = width;

    return sx;
}