dvdsubdec.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/*
 * DVD subtitle decoding for ffmpeg
 * Copyright (c) 2005 Fabrice Bellard.
 *
 * 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 "avcodec.h"
#include "bitstream.h"
#include "colorspace.h"
#include "dsputil.h"

//#define DEBUG

static void yuv_a_to_rgba(const uint8_t *ycbcr, const uint8_t *alpha, uint32_t *rgba, int num_values)
{
    uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
    uint8_t r, g, b;
    int i, y, cb, cr;
    int r_add, g_add, b_add;

    for (i = num_values; i > 0; i--) {
        y = *ycbcr++;
        cb = *ycbcr++;
        cr = *ycbcr++;
        YUV_TO_RGB1_CCIR(cb, cr);
        YUV_TO_RGB2_CCIR(r, g, b, y);
        *rgba++ = (*alpha++ << 24) | (r << 16) | (g << 8) | b;
    }
}

static int dvdsub_init_decoder(AVCodecContext *avctx)
{
    return 0;
}

static int decode_run_2bit(GetBitContext *gb, int *color)
{
    unsigned int v, t;

    v = 0;
    for (t = 1; v < t && t <= 0x40; t <<= 2)
        v = (v << 4) | get_bits(gb, 4);
    *color = v & 3;
    if (v < 4) { /* Code for fill rest of line */
        return INT_MAX;
    }
    return v >> 2;
}

static int decode_run_8bit(GetBitContext *gb, int *color)
{
    int len;
    int has_run = get_bits1(gb);
    if (get_bits1(gb))
        *color = get_bits(gb, 8);
    else
        *color = get_bits(gb, 2);
    if (has_run) {
        if (get_bits1(gb)) {
            len = get_bits(gb, 7);
            if (len == 0)
                len = INT_MAX;
            else
                len += 9;
        } else
            len = get_bits(gb, 3) + 2;
    } else
        len = 1;
    return len;
}

static int decode_rle(uint8_t *bitmap, int linesize, int w, int h,
                      const uint8_t *buf, int start, int buf_size, int is_8bit)
{
    GetBitContext gb;
    int bit_len;
    int x, y, len, color;
    uint8_t *d;

    bit_len = (buf_size - start) * 8;
    init_get_bits(&gb, buf + start, bit_len);

    x = 0;
    y = 0;
    d = bitmap;
    for(;;) {
        if (get_bits_count(&gb) > bit_len)
            return -1;
        if (is_8bit)
            len = decode_run_8bit(&gb, &color);
        else
            len = decode_run_2bit(&gb, &color);
        len = FFMIN(len, w - x);
        memset(d + x, color, len);
        x += len;
        if (x >= w) {
            y++;
            if (y >= h)
                break;
            d += linesize;
            x = 0;
            /* byte align */
            align_get_bits(&gb);
        }
    }
    return 0;
}

static void guess_palette(uint32_t *rgba_palette,
                          uint8_t *colormap,
                          uint8_t *alpha,
                          uint32_t subtitle_color)
{
    uint8_t color_used[16];
    int nb_opaque_colors, i, level, j, r, g, b;

    for(i = 0; i < 4; i++)
        rgba_palette[i] = 0;

    memset(color_used, 0, 16);
    nb_opaque_colors = 0;
    for(i = 0; i < 4; i++) {
        if (alpha[i] != 0 && !color_used[colormap[i]]) {
            color_used[colormap[i]] = 1;
            nb_opaque_colors++;
        }
    }

    if (nb_opaque_colors == 0)
        return;

    j = nb_opaque_colors;
    memset(color_used, 0, 16);
    for(i = 0; i < 4; i++) {
        if (alpha[i] != 0) {
            if (!color_used[colormap[i]])  {
                level = (0xff * j) / nb_opaque_colors;
                r = (((subtitle_color >> 16) & 0xff) * level) >> 8;
                g = (((subtitle_color >> 8) & 0xff) * level) >> 8;
                b = (((subtitle_color >> 0) & 0xff) * level) >> 8;
                rgba_palette[i] = b | (g << 8) | (r << 16) | ((alpha[i] * 17) << 24);
                color_used[colormap[i]] = (i + 1);
                j--;
            } else {
                rgba_palette[i] = (rgba_palette[color_used[colormap[i]] - 1] & 0x00ffffff) |
                                    ((alpha[i] * 17) << 24);
            }
        }
    }
}

#define READ_OFFSET(a) (big_offsets ? AV_RB32(a) : AV_RB16(a))

static int decode_dvd_subtitles(AVSubtitle *sub_header,
                                const uint8_t *buf, int buf_size)
{
    int cmd_pos, pos, cmd, x1, y1, x2, y2, offset1, offset2, next_cmd_pos;
    int big_offsets, offset_size, is_8bit = 0;
    const uint8_t *yuv_palette = 0;
    uint8_t colormap[4], alpha[256];
    int date;
    int i;
    int is_menu = 0;

    if (buf_size < 10)
        return -1;
    sub_header->rects = NULL;
    sub_header->num_rects = 0;
    sub_header->start_display_time = 0;
    sub_header->end_display_time = 0;

    if (AV_RB16(buf) == 0) {   /* HD subpicture with 4-byte offsets */
        big_offsets = 1;
        offset_size = 4;
        cmd_pos = 6;
    } else {
        big_offsets = 0;
        offset_size = 2;
        cmd_pos = 2;
    }

    cmd_pos = READ_OFFSET(buf + cmd_pos);

    while ((cmd_pos + 2 + offset_size) < buf_size) {
        date = AV_RB16(buf + cmd_pos);
        next_cmd_pos = READ_OFFSET(buf + cmd_pos + 2);
#ifdef DEBUG
        av_log(NULL, AV_LOG_INFO, "cmd_pos=0x%04x next=0x%04x date=%d\n",
               cmd_pos, next_cmd_pos, date);
#endif
        pos = cmd_pos + 2 + offset_size;
        offset1 = -1;
        offset2 = -1;
        x1 = y1 = x2 = y2 = 0;
        while (pos < buf_size) {
            cmd = buf[pos++];
#ifdef DEBUG
            av_log(NULL, AV_LOG_INFO, "cmd=%02x\n", cmd);
#endif
            switch(cmd) {
            case 0x00:
                /* menu subpicture */
                is_menu = 1;
                break;
            case 0x01:
                /* set start date */
                sub_header->start_display_time = (date << 10) / 90;
                break;
            case 0x02:
                /* set end date */
                sub_header->end_display_time = (date << 10) / 90;
                break;
            case 0x03:
                /* set colormap */
                if ((buf_size - pos) < 2)
                    goto fail;
                colormap[3] = buf[pos] >> 4;
                colormap[2] = buf[pos] & 0x0f;
                colormap[1] = buf[pos + 1] >> 4;
                colormap[0] = buf[pos + 1] & 0x0f;
                pos += 2;
                break;
            case 0x04:
                /* set alpha */
                if ((buf_size - pos) < 2)
                    goto fail;
                alpha[3] = buf[pos] >> 4;
                alpha[2] = buf[pos] & 0x0f;
                alpha[1] = buf[pos + 1] >> 4;
                alpha[0] = buf[pos + 1] & 0x0f;
                pos += 2;
#ifdef DEBUG
            av_log(NULL, AV_LOG_INFO, "alpha=%x%x%x%x\n", alpha[0],alpha[1],alpha[2],alpha[3]);
#endif
                break;
            case 0x05:
            case 0x85:
                if ((buf_size - pos) < 6)
                    goto fail;
                x1 = (buf[pos] << 4) | (buf[pos + 1] >> 4);
                x2 = ((buf[pos + 1] & 0x0f) << 8) | buf[pos + 2];
                y1 = (buf[pos + 3] << 4) | (buf[pos + 4] >> 4);
                y2 = ((buf[pos + 4] & 0x0f) << 8) | buf[pos + 5];
                if (cmd & 0x80)
                    is_8bit = 1;
#ifdef DEBUG