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 "get_bits.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 int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
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 - packet_time;
44}
45
46static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
47                        AVPacket *avpkt) {
48    const uint8_t *buf = avpkt->data;
49    int buf_size = avpkt->size;
50    AVSubtitle *sub = data;
51    const uint8_t *buf_end = buf + buf_size;
52    uint8_t *bitmap;
53    int w, h, x, y, rlelen, i;
54    int64_t packet_time = 0;
55    GetBitContext gb;
56
57    memset(sub, 0, sizeof(*sub));
58
59    // check that at least header fits
60    if (buf_size < 27 + 7 * 2 + 4 * 3) {
61        av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
62        return -1;
63    }
64
65    // read start and end time
66    if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
67        av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
68        return -1;
69    }
70    if (avpkt->pts != AV_NOPTS_VALUE)
71        packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
72    sub->start_display_time = parse_timecode(buf +  1, packet_time);
73    sub->end_display_time   = parse_timecode(buf + 14, packet_time);
74    buf += 27;
75
76    // read header
77    w = bytestream_get_le16(&buf);
78    h = bytestream_get_le16(&buf);
79    if (avcodec_check_dimensions(avctx, w, h) < 0)
80        return -1;
81    x = bytestream_get_le16(&buf);
82    y = bytestream_get_le16(&buf);
83    // skip bottom right position, it gives no new information
84    bytestream_get_le16(&buf);
85    bytestream_get_le16(&buf);
86    rlelen = bytestream_get_le16(&buf);
87
88    // allocate sub and set values
89    sub->rects =  av_mallocz(sizeof(*sub->rects));
90    sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
91    sub->num_rects = 1;
92    sub->rects[0]->x = x; sub->rects[0]->y = y;
93    sub->rects[0]->w = w; sub->rects[0]->h = h;
94    sub->rects[0]->type = SUBTITLE_BITMAP;
95    sub->rects[0]->pict.linesize[0] = w;
96    sub->rects[0]->pict.data[0] = av_malloc(w * h);
97    sub->rects[0]->nb_colors = 4;
98    sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
99
100    // read palette
101    for (i = 0; i < sub->rects[0]->nb_colors; i++)
102        ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
103    // make all except background (first entry) non-transparent
104    for (i = 1; i < sub->rects[0]->nb_colors; i++)
105        ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
106
107    // process RLE-compressed data
108    rlelen = FFMIN(rlelen, buf_end - buf);
109    init_get_bits(&gb, buf, rlelen * 8);
110    bitmap = sub->rects[0]->pict.data[0];
111    for (y = 0; y < h; y++) {
112        // interlaced: do odd lines
113        if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
114        for (x = 0; x < w; ) {
115            int log2 = ff_log2_tab[show_bits(&gb, 8)];
116            int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
117            int color = get_bits(&gb, 2);
118            run = FFMIN(run, w - x);
119            // run length 0 means till end of row
120            if (!run) run = w - x;
121            memset(bitmap, color, run);
122            bitmap += run;
123            x += run;
124        }
125        // interlaced, skip every second line
126        bitmap += w;
127        align_get_bits(&gb);
128    }
129    *data_size = 1;
130    return buf_size;
131}
132
133AVCodec xsub_decoder = {
134    "xsub",
135    AVMEDIA_TYPE_SUBTITLE,
136    CODEC_ID_XSUB,
137    0,
138    decode_init,
139    NULL,
140    NULL,
141    decode_frame,
142    .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
143};
144