1/*
2 * XSUB subtitle decoder
3 * Copyright (c) 2007 Reimar D��ffinger
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21#include "avcodec.h"
22#include "bitstream.h"
23#include "bytestream.h"
24
25static av_cold int decode_init(AVCodecContext *avctx) {
26    avctx->pix_fmt = PIX_FMT_PAL8;
27    return 0;
28}
29
30static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
31static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
32
33static uint64_t parse_timecode(const uint8_t *buf) {
34    int i;
35    int64_t ms = 0;
36    if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
37        return AV_NOPTS_VALUE;
38    for (i = 0; i < sizeof(tc_offsets); i++) {
39        uint8_t c = buf[tc_offsets[i]] - '0';
40        if (c > 9) return AV_NOPTS_VALUE;
41        ms = (ms + c) * tc_muls[i];
42    }
43    return ms;
44}
45
46static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
47                        const uint8_t *buf, int buf_size) {
48    AVSubtitle *sub = data;
49    const uint8_t *buf_end = buf + buf_size;
50    uint8_t *bitmap;
51    int w, h, x, y, rlelen, i;
52    GetBitContext gb;
53
54    sub->format = 0;
55
56    // check that at least header fits
57    if (buf_size < 27 + 7 * 2 + 4 * 3) {
58        av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
59        return -1;
60    }
61
62    // read start and end time
63    if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
64        av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
65        return -1;
66    }
67    sub->start_display_time = parse_timecode(buf +  1);
68    sub->end_display_time   = parse_timecode(buf + 14);
69    buf += 27;
70
71    // read header
72    w = bytestream_get_le16(&buf);
73    h = bytestream_get_le16(&buf);
74    if (avcodec_check_dimensions(avctx, w, h) < 0)
75        return -1;
76    x = bytestream_get_le16(&buf);
77    y = bytestream_get_le16(&buf);
78    // skip bottom right position, it gives no new information
79    bytestream_get_le16(&buf);
80    bytestream_get_le16(&buf);
81    rlelen = bytestream_get_le16(&buf);
82
83    // allocate sub and set values
84    if (!sub->rects) {
85        sub->rects =  av_mallocz(sizeof(*sub->rects));
86        sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
87        sub->num_rects = 1;
88    }
89    av_freep(&sub->rects[0]->pict.data[0]);
90    sub->rects[0]->x = x; sub->rects[0]->y = y;
91    sub->rects[0]->w = w; sub->rects[0]->h = h;
92    sub->rects[0]->pict.linesize[0] = w;
93    sub->rects[0]->pict.data[0] = av_malloc(w * h);
94    sub->rects[0]->nb_colors = 4;
95    sub->rects[0]->pict.data[1] = av_malloc(sub->rects[0]->nb_colors * 4);
96
97    // read palette
98    for (i = 0; i < sub->rects[0]->nb_colors; i++)
99        ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
100    // make all except background (first entry) non-transparent
101    for (i = 1; i < sub->rects[0]->nb_colors; i++)
102        ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
103
104    // process RLE-compressed data
105    rlelen = FFMIN(rlelen, buf_end - buf);
106    init_get_bits(&gb, buf, rlelen * 8);
107    bitmap = sub->rects[0]->pict.data[0];
108    for (y = 0; y < h; y++) {
109        // interlaced: do odd lines
110        if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
111        for (x = 0; x < w; ) {
112            int log2 = ff_log2_tab[show_bits(&gb, 8)];
113            int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
114            int color = get_bits(&gb, 2);
115            run = FFMIN(run, w - x);
116            // run length 0 means till end of row
117            if (!run) run = w - x;
118            memset(bitmap, color, run);
119            bitmap += run;
120            x += run;
121        }
122        // interlaced, skip every second line
123        bitmap += w;
124        align_get_bits(&gb);
125    }
126    *data_size = 1;
127    return buf_size;
128}
129
130AVCodec xsub_decoder = {
131    "xsub",
132    CODEC_TYPE_SUBTITLE,
133    CODEC_ID_XSUB,
134    0,
135    decode_init,
136    NULL,
137    NULL,
138    decode_frame,
139    .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
140};
141