1 /*
2 * XSUB subtitle decoder
3 * Copyright (c) 2007 Reimar Döffinger
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
22 #include "libavutil/mathematics.h"
23 #include "libavutil/imgutils.h"
24 #include "avcodec.h"
25 #include "get_bits.h"
26 #include "bytestream.h"
27 #include "codec_internal.h"
28
decode_init(AVCodecContext *avctx)29 static av_cold int decode_init(AVCodecContext *avctx) {
30 avctx->pix_fmt = AV_PIX_FMT_PAL8;
31 return 0;
32 }
33
34 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
35 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
36
parse_timecode(const uint8_t *buf, int64_t packet_time)37 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
38 int i;
39 int64_t ms = 0;
40 if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
41 return AV_NOPTS_VALUE;
42 for (i = 0; i < sizeof(tc_offsets); i++) {
43 uint8_t c = buf[tc_offsets[i]] - '0';
44 if (c > 9) return AV_NOPTS_VALUE;
45 ms = (ms + c) * tc_muls[i];
46 }
47 return ms - packet_time;
48 }
49
decode_frame(AVCodecContext *avctx, AVSubtitle *sub, int *got_sub_ptr, const AVPacket *avpkt)50 static int decode_frame(AVCodecContext *avctx, AVSubtitle *sub,
51 int *got_sub_ptr, const AVPacket *avpkt)
52 {
53 const uint8_t *buf = avpkt->data;
54 int buf_size = avpkt->size;
55 AVSubtitleRect *rect;
56 const uint8_t *buf_end = buf + buf_size;
57 uint8_t *bitmap;
58 int w, h, x, y, i, ret;
59 int64_t packet_time = 0;
60 GetBitContext gb;
61 int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
62
63 // check that at least header fits
64 if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {
65 av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);
66 return -1;
67 }
68
69 // read start and end time
70 if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
71 av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
72 return -1;
73 }
74 if (avpkt->pts != AV_NOPTS_VALUE)
75 packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
76 sub->start_display_time = parse_timecode(buf + 1, packet_time);
77 sub->end_display_time = parse_timecode(buf + 14, packet_time);
78 buf += 27;
79
80 // read header
81 w = bytestream_get_le16(&buf);
82 h = bytestream_get_le16(&buf);
83 if (av_image_check_size(w, h, 0, avctx) < 0)
84 return -1;
85 x = bytestream_get_le16(&buf);
86 y = bytestream_get_le16(&buf);
87 // skip bottom right position, it gives no new information
88 bytestream_get_le16(&buf);
89 bytestream_get_le16(&buf);
90 // The following value is supposed to indicate the start offset
91 // (relative to the palette) of the data for the second field,
92 // however there are files in which it has a bogus value and thus
93 // we just ignore it
94 bytestream_get_le16(&buf);
95
96 if (buf_end - buf < h + 3*4)
97 return AVERROR_INVALIDDATA;
98
99 // allocate sub and set values
100 sub->rects = av_mallocz(sizeof(*sub->rects));
101 if (!sub->rects)
102 return AVERROR(ENOMEM);
103
104 sub->rects[0] = rect = av_mallocz(sizeof(*sub->rects[0]));
105 if (!sub->rects[0])
106 return AVERROR(ENOMEM);
107 sub->num_rects = 1;
108 rect->x = x; rect->y = y;
109 rect->w = w; rect->h = h;
110 rect->type = SUBTITLE_BITMAP;
111 rect->linesize[0] = w;
112 rect->data[0] = av_malloc(w * h);
113 rect->nb_colors = 4;
114 rect->data[1] = av_mallocz(AVPALETTE_SIZE);
115 if (!rect->data[0] || !rect->data[1])
116 return AVERROR(ENOMEM);
117
118 // read palette
119 for (i = 0; i < rect->nb_colors; i++)
120 ((uint32_t*)rect->data[1])[i] = bytestream_get_be24(&buf);
121
122 if (!has_alpha) {
123 // make all except background (first entry) non-transparent
124 for (i = 1; i < rect->nb_colors; i++)
125 ((uint32_t *)rect->data[1])[i] |= 0xff000000;
126 } else {
127 for (i = 0; i < rect->nb_colors; i++)
128 ((uint32_t *)rect->data[1])[i] |= (unsigned)*buf++ << 24;
129 }
130
131 // process RLE-compressed data
132 if ((ret = init_get_bits8(&gb, buf, buf_end - buf)) < 0)
133 return ret;
134 bitmap = rect->data[0];
135 for (y = 0; y < h; y++) {
136 // interlaced: do odd lines
137 if (y == (h + 1) / 2) bitmap = rect->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);
146 bitmap += run;
147 x += run;
148 }
149 // interlaced, skip every second line
150 bitmap += w;
151 align_get_bits(&gb);
152 }
153 *got_sub_ptr = 1;
154 return buf_size;
155 }
156
157 const FFCodec ff_xsub_decoder = {
158 .p.name = "xsub",
159 .p.long_name = NULL_IF_CONFIG_SMALL("XSUB"),
160 .p.type = AVMEDIA_TYPE_SUBTITLE,
161 .p.id = AV_CODEC_ID_XSUB,
162 .init = decode_init,
163 FF_CODEC_DECODE_SUB_CB(decode_frame),
164 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
165 };
166