1/*
2 * XSUB subtitle decoder
3 * Copyright (c) 2007 Reimar D��ffinger
4 *
5 * This file is part of Libav.
6 *
7 * Libav 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 * Libav 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 Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include "libavutil/mathematics.h"
23#include "libavutil/imgutils.h"
24#include "avcodec.h"
25#include "get_bits.h"
26#include "bytestream.h"
27
28static av_cold int decode_init(AVCodecContext *avctx) {
29    avctx->pix_fmt = PIX_FMT_PAL8;
30    return 0;
31}
32
33static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
34static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
35
36static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
37    int i;
38    int64_t ms = 0;
39    if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
40        return AV_NOPTS_VALUE;
41    for (i = 0; i < sizeof(tc_offsets); i++) {
42        uint8_t c = buf[tc_offsets[i]] - '0';
43        if (c > 9) return AV_NOPTS_VALUE;
44        ms = (ms + c) * tc_muls[i];
45    }
46    return ms - packet_time;
47}
48
49static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
50                        AVPacket *avpkt) {
51    const uint8_t *buf = avpkt->data;
52    int buf_size = avpkt->size;
53    AVSubtitle *sub = data;
54    const uint8_t *buf_end = buf + buf_size;
55    uint8_t *bitmap;
56    int w, h, x, y, rlelen, i;
57    int64_t packet_time = 0;
58    GetBitContext gb;
59
60    memset(sub, 0, sizeof(*sub));
61
62    // check that at least header fits
63    if (buf_size < 27 + 7 * 2 + 4 * 3) {
64        av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
65        return -1;
66    }
67
68    // read start and end time
69    if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
70        av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
71        return -1;
72    }
73    if (avpkt->pts != AV_NOPTS_VALUE)
74        packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
75    sub->start_display_time = parse_timecode(buf +  1, packet_time);
76    sub->end_display_time   = parse_timecode(buf + 14, packet_time);
77    buf += 27;
78
79    // read header
80    w = bytestream_get_le16(&buf);
81    h = bytestream_get_le16(&buf);
82    if (av_image_check_size(w, h, 0, avctx) < 0)
83        return -1;
84    x = bytestream_get_le16(&buf);
85    y = bytestream_get_le16(&buf);
86    // skip bottom right position, it gives no new information
87    bytestream_get_le16(&buf);
88    bytestream_get_le16(&buf);
89    rlelen = bytestream_get_le16(&buf);
90
91    // allocate sub and set values
92    sub->rects =  av_mallocz(sizeof(*sub->rects));
93    sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
94    sub->num_rects = 1;
95    sub->rects[0]->x = x; sub->rects[0]->y = y;
96    sub->rects[0]->w = w; sub->rects[0]->h = h;
97    sub->rects[0]->type = SUBTITLE_BITMAP;
98    sub->rects[0]->pict.linesize[0] = w;
99    sub->rects[0]->pict.data[0] = av_malloc(w * h);
100    sub->rects[0]->nb_colors = 4;
101    sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
102
103    // read palette
104    for (i = 0; i < sub->rects[0]->nb_colors; i++)
105        ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
106    // make all except background (first entry) non-transparent
107    for (i = 1; i < sub->rects[0]->nb_colors; i++)
108        ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
109
110    // process RLE-compressed data
111    rlelen = FFMIN(rlelen, buf_end - buf);
112    init_get_bits(&gb, buf, rlelen * 8);
113    bitmap = sub->rects[0]->pict.data[0];
114    for (y = 0; y < h; y++) {
115        // interlaced: do odd lines
116        if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
117        for (x = 0; x < w; ) {
118            int log2 = ff_log2_tab[show_bits(&gb, 8)];
119            int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
120            int color = get_bits(&gb, 2);
121            run = FFMIN(run, w - x);
122            // run length 0 means till end of row
123            if (!run) run = w - x;
124            memset(bitmap, color, run);
125            bitmap += run;
126            x += run;
127        }
128        // interlaced, skip every second line
129        bitmap += w;
130        align_get_bits(&gb);
131    }
132    *data_size = 1;
133    return buf_size;
134}
135
136AVCodec ff_xsub_decoder = {
137    .name      = "xsub",
138    .type      = AVMEDIA_TYPE_SUBTITLE,
139    .id        = CODEC_ID_XSUB,
140    .init      = decode_init,
141    .decode    = decode_frame,
142    .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
143};
144