2 * XSUB subtitle decoder
3 * Copyright (c) 2007 Reimar Döffinger
5 * This file is part of Libav.
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.
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.
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
22 #include "libavutil/mathematics.h"
23 #include "libavutil/imgutils.h"
26 #include "bytestream.h"
28 static av_cold int decode_init(AVCodecContext *avctx) {
29 avctx->pix_fmt = AV_PIX_FMT_PAL8;
33 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
34 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
36 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
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];
46 return ms - packet_time;
49 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
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;
57 int64_t packet_time = 0;
60 memset(sub, 0, sizeof(*sub));
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");
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");
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);
80 w = bytestream_get_le16(&buf);
81 h = bytestream_get_le16(&buf);
82 if (av_image_check_size(w, h, 0, avctx) < 0)
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 // The following value is supposed to indicate the start offset
90 // (relative to the palette) of the data for the second field,
91 // however there are files in which it has a bogus value and thus
93 bytestream_get_le16(&buf);
95 // allocate sub and set values
96 sub->rects = av_mallocz(sizeof(*sub->rects));
97 sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
99 sub->rects[0]->x = x; sub->rects[0]->y = y;
100 sub->rects[0]->w = w; sub->rects[0]->h = h;
101 sub->rects[0]->type = SUBTITLE_BITMAP;
102 sub->rects[0]->pict.linesize[0] = w;
103 sub->rects[0]->pict.data[0] = av_malloc(w * h);
104 sub->rects[0]->nb_colors = 4;
105 sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
108 for (i = 0; i < sub->rects[0]->nb_colors; i++)
109 ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
110 // make all except background (first entry) non-transparent
111 for (i = 1; i < sub->rects[0]->nb_colors; i++)
112 ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
114 // process RLE-compressed data
115 init_get_bits(&gb, buf, (buf_end - buf) * 8);
116 bitmap = sub->rects[0]->pict.data[0];
117 for (y = 0; y < h; y++) {
118 // interlaced: do odd lines
119 if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
120 for (x = 0; x < w; ) {
121 int log2 = ff_log2_tab[show_bits(&gb, 8)];
122 int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
123 int color = get_bits(&gb, 2);
124 run = FFMIN(run, w - x);
125 // run length 0 means till end of row
126 if (!run) run = w - x;
127 memset(bitmap, color, run);
131 // interlaced, skip every second line
139 AVCodec ff_xsub_decoder = {
141 .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
142 .type = AVMEDIA_TYPE_SUBTITLE,
143 .id = AV_CODEC_ID_XSUB,
145 .decode = decode_frame,