2 * 3GPP TS 26.245 Timed Text decoder
3 * Copyright (c) 2012 Philip Langdale <philipl@overt.org>
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
24 #include "libavutil/avstring.h"
25 #include "libavutil/common.h"
26 #include "libavutil/bprint.h"
27 #include "libavutil/intreadwrite.h"
29 static int text_to_ass(AVBPrint
*buf
, const char *text
, const char *text_end
)
31 while (text
< text_end
) {
36 av_bprintf(buf
, "\\N");
39 av_bprint_chars(buf
, *text
, 1);
48 static int mov_text_init(AVCodecContext
*avctx
) {
50 * TODO: Handle the default text style.
51 * NB: Most players ignore styles completely, with the result that
52 * it's very common to find files where the default style is broken
53 * and respecting it results in a worse experience than ignoring it.
55 return ff_ass_subtitle_header_default(avctx
);
58 static int mov_text_decode_frame(AVCodecContext
*avctx
,
59 void *data
, int *got_sub_ptr
, AVPacket
*avpkt
)
61 AVSubtitle
*sub
= data
;
62 int ret
, ts_start
, ts_end
;
64 const char *ptr
= avpkt
->data
;
67 if (!ptr
|| avpkt
->size
< 2)
68 return AVERROR_INVALIDDATA
;
71 * A packet of size two with value zero is an empty subtitle
72 * used to mark the end of the previous non-empty subtitle.
73 * We can just drop them here as we have duration information
74 * already. If the value is non-zero, then it's technically a
78 return AV_RB16(ptr
) == 0 ? 0 : AVERROR_INVALIDDATA
;
81 * The first two bytes of the packet are the length of the text string
82 * In complex cases, there are style descriptors appended to the string
83 * so we can't just assume the packet size is the string size.
85 end
= ptr
+ FFMIN(2 + AV_RB16(ptr
), avpkt
->size
);
88 ts_start
= av_rescale_q(avpkt
->pts
,
91 ts_end
= av_rescale_q(avpkt
->pts
+ avpkt
->duration
,
95 // Note that the spec recommends lines be no longer than 2048 characters.
96 av_bprint_init(&buf
, 0, AV_BPRINT_SIZE_UNLIMITED
);
97 text_to_ass(&buf
, ptr
, end
);
98 ret
= ff_ass_add_rect_bprint(sub
, &buf
, ts_start
, ts_end
-ts_start
);
99 av_bprint_finalize(&buf
, NULL
);
102 *got_sub_ptr
= sub
->num_rects
> 0;
106 AVCodec ff_movtext_decoder
= {
108 .long_name
= NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
109 .type
= AVMEDIA_TYPE_SUBTITLE
,
110 .id
= AV_CODEC_ID_MOV_TEXT
,
111 .init
= mov_text_init
,
112 .decode
= mov_text_decode_frame
,