FFmpeg
ttmlenc.c
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1 /*
2  * TTML subtitle muxer
3  * Copyright (c) 2020 24i
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 /**
23  * @file
24  * TTML subtitle muxer
25  * @see https://www.w3.org/TR/ttml1/
26  * @see https://www.w3.org/TR/ttml2/
27  * @see https://www.w3.org/TR/ttml-imsc/rec
28  */
29 
30 #include "libavutil/avstring.h"
31 #include "avformat.h"
32 #include "internal.h"
33 #include "mux.h"
34 #include "ttmlenc.h"
35 #include "libavcodec/ttmlenc.h"
36 #include "libavutil/internal.h"
37 
38 enum TTMLPacketType {
39  PACKET_TYPE_PARAGRAPH,
40  PACKET_TYPE_DOCUMENT,
41 };
42 
43 struct TTMLHeaderParameters {
44  const char *tt_element_params;
45  const char *pre_body_elements;
46 };
47 
48 typedef struct TTMLMuxContext {
49  enum TTMLPacketType input_type;
50  unsigned int document_written;
51 } TTMLMuxContext;
52 
53 static const char ttml_header_text[] =
54 "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
55 "<tt\n"
56 "%s"
57 " xml:lang=\"%s\">\n"
58 "%s"
59 " <body>\n"
60 " <div>\n";
61 
62 static const char ttml_footer_text[] =
63 " </div>\n"
64 " </body>\n"
65 "</tt>\n";
66 
67 static void ttml_write_time(AVIOContext *pb, const char tag[],
68  int64_t millisec)
69 {
70  int64_t sec, min, hour;
71  sec = millisec / 1000;
72  millisec -= 1000 * sec;
73  min = sec / 60;
74  sec -= 60 * min;
75  hour = min / 60;
76  min -= 60 * hour;
77 
78  avio_printf(pb, "%s=\"%02"PRId64":%02"PRId64":%02"PRId64".%03"PRId64"\"",
79  tag, hour, min, sec, millisec);
80 }
81 
82 static int ttml_set_header_values_from_extradata(
83  AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
84 {
85  size_t additional_data_size =
86  par->extradata_size - TTMLENC_EXTRADATA_SIGNATURE_SIZE;
87  char *value =
88  (char *)par->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE;
89  size_t value_size = av_strnlen(value, additional_data_size);
90  struct TTMLHeaderParameters local_params = { 0 };
91 
92  if (!additional_data_size) {
93  // simple case, we don't have to go through local_params and just
94  // set default fall-back values (for old extradata format).
95  header_params->tt_element_params = TTML_DEFAULT_NAMESPACING;
96  header_params->pre_body_elements = "";
97 
98  return 0;
99  }
100 
101  if (value_size == additional_data_size ||
102  value[value_size] != '\0')
103  return AVERROR_INVALIDDATA;
104 
105  local_params.tt_element_params = value;
106 
107  additional_data_size -= value_size + 1;
108  value += value_size + 1;
109  if (!additional_data_size)
110  return AVERROR_INVALIDDATA;
111 
112  value_size = av_strnlen(value, additional_data_size);
113  if (value_size == additional_data_size ||
114  value[value_size] != '\0')
115  return AVERROR_INVALIDDATA;
116 
117  local_params.pre_body_elements = value;
118 
119  *header_params = local_params;
120 
121  return 0;
122 }
123 
124 static int ttml_write_header(AVFormatContext *ctx)
125 {
126  TTMLMuxContext *ttml_ctx = ctx->priv_data;
127  ttml_ctx->document_written = 0;
128 
129  if (ctx->nb_streams != 1 ||
130  ctx->streams[0]->codecpar->codec_id != AV_CODEC_ID_TTML) {
131  av_log(ctx, AV_LOG_ERROR, "Exactly one TTML stream is required!\n");
132  return AVERROR(EINVAL);
133  }
134 
135  {
136  AVStream *st = ctx->streams[0];
137  AVIOContext *pb = ctx->pb;
138 
139  AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL,
140  0);
141  const char *printed_lang = (lang && lang->value) ? lang->value : "";
142 
143  ttml_ctx->input_type = ff_is_ttml_stream_paragraph_based(st->codecpar) ?
144  PACKET_TYPE_PARAGRAPH :
145  PACKET_TYPE_DOCUMENT;
146 
147  avpriv_set_pts_info(st, 64, 1, 1000);
148 
149  if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH) {
150  struct TTMLHeaderParameters header_params;
151  int ret = ttml_set_header_values_from_extradata(
152  st->codecpar, &header_params);
153  if (ret < 0) {
154  av_log(ctx, AV_LOG_ERROR,
155  "Failed to parse TTML header values from extradata: "
156  "%s!\n", av_err2str(ret));
157  return ret;
158  }
159 
160  avio_printf(pb, ttml_header_text,
161  header_params.tt_element_params,
162  printed_lang,
163  header_params.pre_body_elements);
164  }
165  }
166 
167  return 0;
168 }
169 
170 static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
171 {
172  TTMLMuxContext *ttml_ctx = ctx->priv_data;
173  AVIOContext *pb = ctx->pb;
174 
175  switch (ttml_ctx->input_type) {
176  case PACKET_TYPE_PARAGRAPH:
177  // write out a paragraph element with the given contents.
178  avio_printf(pb, " <p\n");
179  ttml_write_time(pb, " begin", pkt->pts);
180  avio_w8(pb, '\n');
181  ttml_write_time(pb, " end", pkt->pts + pkt->duration);
182  avio_printf(pb, ">");
183  avio_write(pb, pkt->data, pkt->size);
184  avio_printf(pb, "</p>\n");
185  break;
186  case PACKET_TYPE_DOCUMENT:
187  // dump the given document out as-is.
188  if (ttml_ctx->document_written) {
189  av_log(ctx, AV_LOG_ERROR,
190  "Attempting to write multiple TTML documents into a "
191  "single document! The XML specification forbids this "
192  "as there has to be a single root tag.\n");
193  return AVERROR(EINVAL);
194  }
195  avio_write(pb, pkt->data, pkt->size);
196  ttml_ctx->document_written = 1;
197  break;
198  default:
199  av_log(ctx, AV_LOG_ERROR,
200  "Internal error: invalid TTML input packet type: %d!\n",
201  ttml_ctx->input_type);
202  return AVERROR_BUG;
203  }
204 
205  return 0;
206 }
207 
208 static int ttml_write_trailer(AVFormatContext *ctx)
209 {
210  TTMLMuxContext *ttml_ctx = ctx->priv_data;
211  AVIOContext *pb = ctx->pb;
212 
213  if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH)
214  avio_printf(pb, ttml_footer_text);
215 
216  return 0;
217 }
218 
219 const FFOutputFormat ff_ttml_muxer = {
220  .p.name = "ttml",
221  .p.long_name = NULL_IF_CONFIG_SMALL("TTML subtitle"),
222  .p.extensions = "ttml",
223  .p.mime_type = "text/ttml",
224  .priv_data_size = sizeof(TTMLMuxContext),
225  .p.flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
226  AVFMT_TS_NONSTRICT,
227  .p.subtitle_codec = AV_CODEC_ID_TTML,
228  .write_header = ttml_write_header,
229  .write_packet = ttml_write_packet,
230  .write_trailer = ttml_write_trailer,
231 };
AVCodecParameters::extradata
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: codec_par.h:76
TTMLHeaderParameters
Definition: ttmlenc.c:43
AVOutputFormat::name
const char * name
Definition: avformat.h:508
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
ttml_write_trailer
static int ttml_write_trailer(AVFormatContext *ctx)
Definition: ttmlenc.c:208
AVCodecParameters
This struct describes the properties of an encoded stream.
Definition: codec_par.h:54
AVFMT_VARIABLE_FPS
#define AVFMT_VARIABLE_FPS
Format allows variable fps.
Definition: avformat.h:482
ttml_write_packet
static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: ttmlenc.c:170
AVFormatContext::streams
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1172
AVPacket::data
uint8_t * data
Definition: packet.h:374
AVPacket::duration
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:392
TTMLHeaderParameters::tt_element_params
const char * tt_element_params
Definition: ttmlenc.c:44
FFOutputFormat::p
AVOutputFormat p
The public AVOutputFormat.
Definition: mux.h:34
TTMLENC_EXTRADATA_SIGNATURE_SIZE
#define TTMLENC_EXTRADATA_SIGNATURE_SIZE
Definition: ttmlenc.h:26
avpriv_set_pts_info
void avpriv_set_pts_info(AVStream *st, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: avformat.c:771
PACKET_TYPE_PARAGRAPH
@ PACKET_TYPE_PARAGRAPH
Definition: ttmlenc.c:39
pkt
AVPacket * pkt
Definition: movenc.c:59
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
ttml_footer_text
static const char ttml_footer_text[]
Definition: ttmlenc.c:62
ttml_header_text
static const char ttml_header_text[]
Definition: ttmlenc.c:53
av_dict_get
AVDictionaryEntry * av_dict_get(const AVDictionary *m, const char *key, const AVDictionaryEntry *prev, int flags)
Get a dictionary entry with matching key.
Definition: dict.c:60
ttml_write_time
static void ttml_write_time(AVIOContext *pb, const char tag[], int64_t millisec)
Definition: ttmlenc.c:67
TTMLMuxContext
Definition: ttmlenc.c:48
TTMLPacketType
TTMLPacketType
Definition: ttmlenc.c:38
ctx
AVFormatContext * ctx
Definition: movenc.c:48
AVFormatContext
Format I/O context.
Definition: avformat.h:1104
ttml_write_header
static int ttml_write_header(AVFormatContext *ctx)
Definition: ttmlenc.c:124
internal.h
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:861
TTMLHeaderParameters::pre_body_elements
const char * pre_body_elements
Definition: ttmlenc.c:45
NULL
#define NULL
Definition: coverity.c:32
av_strnlen
size_t static size_t av_strnlen(const char *s, size_t len)
Get the count of continuous non zero chars starting from the beginning.
Definition: avstring.h:142
AVFormatContext::pb
AVIOContext * pb
I/O context.
Definition: avformat.h:1146
TTMLMuxContext::input_type
enum TTMLPacketType input_type
Definition: ttmlenc.c:49
AVStream::metadata
AVDictionary * metadata
Definition: avformat.h:918
FFOutputFormat
Definition: mux.h:30
avio_w8
void avio_w8(AVIOContext *s, int b)
Definition: aviobuf.c:200
AVCodecParameters::extradata_size
int extradata_size
Size of the extradata content in bytes.
Definition: codec_par.h:80
AVFormatContext::nb_streams
unsigned int nb_streams
Number of elements in AVFormatContext.streams.
Definition: avformat.h:1160
AVIOContext
Bytestream IO Context.
Definition: avio.h:166
AVPacket::size
int size
Definition: packet.h:375
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:115
TTMLMuxContext::document_written
unsigned int document_written
Definition: ttmlenc.c:50
av_err2str
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: error.h:121
PACKET_TYPE_DOCUMENT
@ PACKET_TYPE_DOCUMENT
Definition: ttmlenc.c:40
avio_write
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:222
ttml_set_header_values_from_extradata
static int ttml_set_header_values_from_extradata(AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
Definition: ttmlenc.c:82
ff_ttml_muxer
const FFOutputFormat ff_ttml_muxer
Definition: ttmlenc.c:219
AVFMT_GLOBALHEADER
#define AVFMT_GLOBALHEADER
Format wants global header.
Definition: avformat.h:478
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:367
internal.h
AV_CODEC_ID_TTML
@ AV_CODEC_ID_TTML
Definition: codec_id.h:568
value
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default value
Definition: writing_filters.txt:86
AVFMT_TS_NONSTRICT
#define AVFMT_TS_NONSTRICT
Format does not require strictly increasing timestamps, but they must still be monotonic.
Definition: avformat.h:489
tag
uint32_t tag
Definition: movenc.c:1641
ret
ret
Definition: filter_design.txt:187
AVStream
Stream structure.
Definition: avformat.h:838
avformat.h
avio_printf
int avio_printf(AVIOContext *s, const char *fmt,...) av_printf_format(2
Writes a formatted string to the context.
ttmlenc.h
TTML_DEFAULT_NAMESPACING
#define TTML_DEFAULT_NAMESPACING
Definition: ttmlenc.h:28
AVDictionaryEntry
Definition: dict.h:89
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:62
AVPacket
This structure stores compressed data.
Definition: packet.h:351
AVERROR_BUG
#define AVERROR_BUG
Internal bug, also see AVERROR_BUG2.
Definition: error.h:52
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
AVDictionaryEntry::value
char * value
Definition: dict.h:91
avstring.h
ff_is_ttml_stream_paragraph_based
static unsigned int ff_is_ttml_stream_paragraph_based(const AVCodecParameters *codecpar)
Definition: ttmlenc.h:28
AVFormatContext::priv_data
void * priv_data
Format private data.
Definition: avformat.h:1132
min
float min
Definition: vorbis_enc_data.h:429
mux.h
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