2 * XSUB subtitle decoder
3 * Copyright (c) 2007 Reimar Döffinger
5 * This file is part of FFmpeg.
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.
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.
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
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;
59 int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
61 // check that at least header fits
62 if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {
63 av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);
67 // read start and end time
68 if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
69 av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
72 if (avpkt->pts != AV_NOPTS_VALUE)
73 packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
74 sub->start_display_time = parse_timecode(buf + 1, packet_time);
75 sub->end_display_time = parse_timecode(buf + 14, packet_time);
79 w = bytestream_get_le16(&buf);
80 h = bytestream_get_le16(&buf);
81 if (av_image_check_size(w, h, 0, avctx) < 0)
83 x = bytestream_get_le16(&buf);
84 y = bytestream_get_le16(&buf);
85 // skip bottom right position, it gives no new information
86 bytestream_get_le16(&buf);
87 bytestream_get_le16(&buf);
88 // The following value is supposed to indicate the start offset
89 // (relative to the palette) of the data for the second field,
90 // however there are files in which it has a bogus value and thus
92 bytestream_get_le16(&buf);
94 // allocate sub and set values
95 sub->rects = av_mallocz(sizeof(*sub->rects));
97 return AVERROR(ENOMEM);
99 sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
100 if (!sub->rects[0]) {
101 av_freep(&sub->rects);
102 return AVERROR(ENOMEM);
104 sub->rects[0]->x = x; sub->rects[0]->y = y;
105 sub->rects[0]->w = w; sub->rects[0]->h = h;
106 sub->rects[0]->type = SUBTITLE_BITMAP;
107 sub->rects[0]->pict.linesize[0] = w;
108 sub->rects[0]->pict.data[0] = av_malloc(w * h);
109 sub->rects[0]->nb_colors = 4;
110 sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
111 if (!sub->rects[0]->pict.data[0] || !sub->rects[0]->pict.data[1]) {
112 av_freep(&sub->rects[0]);
113 av_freep(&sub->rects);
114 return AVERROR(ENOMEM);
120 for (i = 0; i < sub->rects[0]->nb_colors; i++)
121 ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
124 // make all except background (first entry) non-transparent
125 for (i = 1; i < sub->rects[0]->nb_colors; i++)
126 ((uint32_t *)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
128 for (i = 0; i < sub->rects[0]->nb_colors; i++)
129 ((uint32_t *)sub->rects[0]->pict.data[1])[i] |= *buf++ << 24;
132 // process RLE-compressed data
133 init_get_bits(&gb, buf, (buf_end - buf) * 8);
134 bitmap = sub->rects[0]->pict.data[0];
135 for (y = 0; y < h; y++) {
136 // interlaced: do odd lines
137 if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
138 for (x = 0; x < w; ) {
139 int log2 = ff_log2_tab[show_bits(&gb, 8)];
140 int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
141 int color = get_bits(&gb, 2);
142 run = FFMIN(run, w - x);
143 // run length 0 means till end of row
144 if (!run) run = w - x;
145 memset(bitmap, color, run);
149 // interlaced, skip every second line
157 AVCodec ff_xsub_decoder = {
159 .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
160 .type = AVMEDIA_TYPE_SUBTITLE,
161 .id = AV_CODEC_ID_XSUB,
163 .decode = decode_frame,