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2ba45a60 DM |
1 | /* |
2 | * 3GPP TS 26.245 Timed Text decoder | |
3 | * Copyright (c) 2012 Philip Langdale <philipl@overt.org> | |
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 "avcodec.h" | |
23 | #include "ass.h" | |
24 | #include "libavutil/avstring.h" | |
25 | #include "libavutil/common.h" | |
26 | #include "libavutil/bprint.h" | |
27 | #include "libavutil/intreadwrite.h" | |
28 | ||
29 | static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end) | |
30 | { | |
31 | while (text < text_end) { | |
32 | switch (*text) { | |
33 | case '\r': | |
34 | break; | |
35 | case '\n': | |
36 | av_bprintf(buf, "\\N"); | |
37 | break; | |
38 | default: | |
39 | av_bprint_chars(buf, *text, 1); | |
40 | break; | |
41 | } | |
42 | text++; | |
43 | } | |
44 | ||
45 | av_bprintf(buf, "\r\n"); | |
46 | return 0; | |
47 | } | |
48 | ||
49 | static int mov_text_init(AVCodecContext *avctx) { | |
50 | /* | |
51 | * TODO: Handle the default text style. | |
52 | * NB: Most players ignore styles completely, with the result that | |
53 | * it's very common to find files where the default style is broken | |
54 | * and respecting it results in a worse experience than ignoring it. | |
55 | */ | |
56 | return ff_ass_subtitle_header_default(avctx); | |
57 | } | |
58 | ||
59 | static int mov_text_decode_frame(AVCodecContext *avctx, | |
60 | void *data, int *got_sub_ptr, AVPacket *avpkt) | |
61 | { | |
62 | AVSubtitle *sub = data; | |
63 | int ts_start, ts_end; | |
64 | AVBPrint buf; | |
65 | const char *ptr = avpkt->data; | |
66 | const char *end; | |
67 | ||
68 | if (!ptr || avpkt->size < 2) | |
69 | return AVERROR_INVALIDDATA; | |
70 | ||
71 | /* | |
72 | * A packet of size two with value zero is an empty subtitle | |
73 | * used to mark the end of the previous non-empty subtitle. | |
74 | * We can just drop them here as we have duration information | |
75 | * already. If the value is non-zero, then it's technically a | |
76 | * bad packet. | |
77 | */ | |
78 | if (avpkt->size == 2) | |
79 | return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA; | |
80 | ||
81 | /* | |
82 | * The first two bytes of the packet are the length of the text string | |
83 | * In complex cases, there are style descriptors appended to the string | |
84 | * so we can't just assume the packet size is the string size. | |
85 | */ | |
86 | end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size); | |
87 | ptr += 2; | |
88 | ||
89 | ts_start = av_rescale_q(avpkt->pts, | |
90 | avctx->time_base, | |
91 | (AVRational){1,100}); | |
92 | ts_end = av_rescale_q(avpkt->pts + avpkt->duration, | |
93 | avctx->time_base, | |
94 | (AVRational){1,100}); | |
95 | ||
96 | // Note that the spec recommends lines be no longer than 2048 characters. | |
97 | av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED); | |
98 | text_to_ass(&buf, ptr, end); | |
99 | ||
100 | if (!av_bprint_is_complete(&buf)) | |
101 | return AVERROR(ENOMEM); | |
102 | ||
103 | ff_ass_add_rect(sub, buf.str, ts_start, ts_end-ts_start, 0); | |
104 | *got_sub_ptr = sub->num_rects > 0; | |
105 | av_bprint_finalize(&buf, NULL); | |
106 | return avpkt->size; | |
107 | } | |
108 | ||
109 | AVCodec ff_movtext_decoder = { | |
110 | .name = "mov_text", | |
111 | .long_name = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"), | |
112 | .type = AVMEDIA_TYPE_SUBTITLE, | |
113 | .id = AV_CODEC_ID_MOV_TEXT, | |
114 | .init = mov_text_init, | |
115 | .decode = mov_text_decode_frame, | |
116 | }; |