FFmpeg/libavcodec/vulkan/ffv1_enc_vlc.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 RLEState {
    int count;
    int diff;
    int index;
    bool mode;
};

void calc_new_state(inout RLEState state, int context)
{
    if (context == 0)
        state.mode = false;

    if (!state.mode)
        return;

    if (state.diff > 0) {
        while (state.count >= (1 << log2_run[state.index])) {
            state.count -= 1 << log2_run[state.index];
            state.index++;
        }
        if (state.index > 0)
            state.index--;
        state.count = 0;
        state.mode = false;
        if (state.diff > 0)
            state.diff--;
    } else {
        state.count++;
    }
}

void encode_line(inout SliceContext sc, uint64_t state,
                 int y, int p, int comp, int bits, inout int run_index)
{
    ivec2 sp = sc.slice_pos;

    int w = sc.slice_dim.x;
    if (p > 0 && p < 3) {
        w >>= chroma_shift.x;
        sp >>= chroma_shift;
    }

    int run_count = 0;
    bool run_mode = false;

    for (int x = 0; x < w; x++) {
        ivec2 d = get_diff(sp + ivec2(x, y), ivec2(x, y), p, comp, w, bits);

        if (d[0] == 0)
            run_mode = true;

        if (run_mode) {
            if (d[1] != 0) {
                /* A very unlikely loop */
                while (run_count >= 1 << log2_run[run_index]) {
                    run_count -= 1 << log2_run[run_index];
                    run_index++;
                    put_bits(sc.pb, 1, 1);
                }

                put_bits(sc.pb, 1 + log2_run[run_index], run_count);
                if (run_index != 0)
                    run_index--;
                run_count = 0;
                run_mode  = false;
                if (d[1] > 0)
                    d[1]--;
            } else {
                run_count++;
            }
        }

        if (!run_mode) {
            VlcState sb = VlcState(state + VLC_STATE_SIZE*d[0]);
            Symbol sym = get_vlc_symbol(sb, d[1], bits);
            put_bits(sc.pb, sym.bits, sym.val);
        }
    }

    if (run_mode) {
        while (run_count >= (1 << log2_run[run_index])) {
            run_count -= 1 << log2_run[run_index];
            run_index++;
            put_bits(sc.pb, 1, 1);
        }

        if (run_count > 0)
            put_bits(sc.pb, 1, 1);
    }
}