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 "ttmlenc.h"
34 #include "libavcodec/ttmlenc.h"
35 #include "libavutil/internal.h"
36 
37 enum TTMLPacketType {
38  PACKET_TYPE_PARAGRAPH,
39  PACKET_TYPE_DOCUMENT,
40 };
41 
42 struct TTMLHeaderParameters {
43  const char *tt_element_params;
44  const char *pre_body_elements;
45 };
46 
47 typedef struct TTMLMuxContext {
48  enum TTMLPacketType input_type;
49  unsigned int document_written;
50 } TTMLMuxContext;
51 
52 static const char ttml_header_text[] =
53 "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
54 "<tt\n"
55 "%s"
56 " xml:lang=\"%s\">\n"
57 "%s"
58 " <body>\n"
59 " <div>\n";
60 
61 static const char ttml_footer_text[] =
62 " </div>\n"
63 " </body>\n"
64 "</tt>\n";
65 
66 static void ttml_write_time(AVIOContext *pb, const char tag[],
67  int64_t millisec)
68 {
69  int64_t sec, min, hour;
70  sec = millisec / 1000;
71  millisec -= 1000 * sec;
72  min = sec / 60;
73  sec -= 60 * min;
74  hour = min / 60;
75  min -= 60 * hour;
76 
77  avio_printf(pb, "%s=\"%02"PRId64":%02"PRId64":%02"PRId64".%03"PRId64"\"",
78  tag, hour, min, sec, millisec);
79 }
80 
81 static int ttml_set_header_values_from_extradata(
82  AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
83 {
84  size_t additional_data_size =
85  par->extradata_size - TTMLENC_EXTRADATA_SIGNATURE_SIZE;
86  char *value =
87  (char *)par->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE;
88  size_t value_size = av_strnlen(value, additional_data_size);
89  struct TTMLHeaderParameters local_params = { 0 };
90 
91  if (!additional_data_size) {
92  // simple case, we don't have to go through local_params and just
93  // set default fall-back values (for old extradata format).
94  header_params->tt_element_params = ttml_default_namespacing;
95  header_params->pre_body_elements = "";
96 
97  return 0;
98  }
99 
100  if (value_size == additional_data_size ||
101  value[value_size] != '\0')
102  return AVERROR_INVALIDDATA;
103 
104  local_params.tt_element_params = value;
105 
106  additional_data_size -= value_size + 1;
107  value += value_size + 1;
108  if (!additional_data_size)
109  return AVERROR_INVALIDDATA;
110 
111  value_size = av_strnlen(value, additional_data_size);
112  if (value_size == additional_data_size ||
113  value[value_size] != '\0')
114  return AVERROR_INVALIDDATA;
115 
116  local_params.pre_body_elements = value;
117 
118  *header_params = local_params;
119 
120  return 0;
121 }
122 
123 static int ttml_write_header(AVFormatContext *ctx)
124 {
125  TTMLMuxContext *ttml_ctx = ctx->priv_data;
126  ttml_ctx->document_written = 0;
127 
128  if (ctx->nb_streams != 1 ||
129  ctx->streams[0]->codecpar->codec_id != AV_CODEC_ID_TTML) {
130  av_log(ctx, AV_LOG_ERROR, "Exactly one TTML stream is required!\n");
131  return AVERROR(EINVAL);
132  }
133 
134  {
135  AVStream *st = ctx->streams[0];
136  AVIOContext *pb = ctx->pb;
137 
138  AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL,
139  0);
140  const char *printed_lang = (lang && lang->value) ? lang->value : "";
141 
142  ttml_ctx->input_type = ff_is_ttml_stream_paragraph_based(st->codecpar) ?
143  PACKET_TYPE_PARAGRAPH :
144  PACKET_TYPE_DOCUMENT;
145 
146  avpriv_set_pts_info(st, 64, 1, 1000);
147 
148  if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH) {
149  struct TTMLHeaderParameters header_params;
150  int ret = ttml_set_header_values_from_extradata(
151  st->codecpar, &header_params);
152  if (ret < 0) {
153  av_log(ctx, AV_LOG_ERROR,
154  "Failed to parse TTML header values from extradata: "
155  "%s!\n", av_err2str(ret));
156  return ret;
157  }
158 
159  avio_printf(pb, ttml_header_text,
160  header_params.tt_element_params,
161  printed_lang,
162  header_params.pre_body_elements);
163  }
164  }
165 
166  return 0;
167 }
168 
169 static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
170 {
171  TTMLMuxContext *ttml_ctx = ctx->priv_data;
172  AVIOContext *pb = ctx->pb;
173 
174  switch (ttml_ctx->input_type) {
175  case PACKET_TYPE_PARAGRAPH:
176  // write out a paragraph element with the given contents.
177  avio_printf(pb, " <p\n");
178  ttml_write_time(pb, " begin", pkt->pts);
179  avio_w8(pb, '\n');
180  ttml_write_time(pb, " end", pkt->pts + pkt->duration);
181  avio_printf(pb, ">");
182  avio_write(pb, pkt->data, pkt->size);
183  avio_printf(pb, "</p>\n");
184  break;
185  case PACKET_TYPE_DOCUMENT:
186  // dump the given document out as-is.
187  if (ttml_ctx->document_written) {
188  av_log(ctx, AV_LOG_ERROR,
189  "Attempting to write multiple TTML documents into a "
190  "single document! The XML specification forbids this "
191  "as there has to be a single root tag.\n");
192  return AVERROR(EINVAL);
193  }
194  avio_write(pb, pkt->data, pkt->size);
195  ttml_ctx->document_written = 1;
196  break;
197  default:
198  av_log(ctx, AV_LOG_ERROR,
199  "Internal error: invalid TTML input packet type: %d!\n",
200  ttml_ctx->input_type);
201  return AVERROR_BUG;
202  }
203 
204  return 0;
205 }
206 
207 static int ttml_write_trailer(AVFormatContext *ctx)
208 {
209  TTMLMuxContext *ttml_ctx = ctx->priv_data;
210  AVIOContext *pb = ctx->pb;
211 
212  if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH)
213  avio_printf(pb, ttml_footer_text);
214 
215  return 0;
216 }
217 
218 const AVOutputFormat ff_ttml_muxer = {
219  .name = "ttml",
220  .long_name = NULL_IF_CONFIG_SMALL("TTML subtitle"),
221  .extensions = "ttml",
222  .mime_type = "text/ttml",
223  .priv_data_size = sizeof(TTMLMuxContext),
224  .flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
225  AVFMT_TS_NONSTRICT,
226  .subtitle_codec = AV_CODEC_ID_TTML,
227  .write_header = ttml_write_header,
228  .write_packet = ttml_write_packet,
229  .write_trailer = ttml_write_trailer,
230 };
AVCodecParameters::extradata
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: codec_par.h:74
TTMLHeaderParameters
Definition: ttmlenc.c:42
AVOutputFormat::name
const char * name
Definition: avformat.h:504
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:207
AVCodecParameters
This struct describes the properties of an encoded stream.
Definition: codec_par.h:52
AVFMT_VARIABLE_FPS
#define AVFMT_VARIABLE_FPS
Format allows variable fps.
Definition: avformat.h:478
ttml_write_packet
static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: ttmlenc.c:169
AVFormatContext::streams
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1268
AVPacket::data
uint8_t * data
Definition: packet.h:373
AVPacket::duration
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:391
TTMLHeaderParameters::tt_element_params
const char * tt_element_params
Definition: ttmlenc.c:43
TTMLENC_EXTRADATA_SIGNATURE_SIZE
#define TTMLENC_EXTRADATA_SIGNATURE_SIZE
Definition: ttmlenc.h:26
PACKET_TYPE_PARAGRAPH
@ PACKET_TYPE_PARAGRAPH
Definition: ttmlenc.c:38
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:61
ttml_header_text
static const char ttml_header_text[]
Definition: ttmlenc.c:52
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:40
ttml_write_time
static void ttml_write_time(AVIOContext *pb, const char tag[], int64_t millisec)
Definition: ttmlenc.c:66
TTMLMuxContext
Definition: ttmlenc.c:47
TTMLPacketType
TTMLPacketType
Definition: ttmlenc.c:37
ctx
AVFormatContext * ctx
Definition: movenc.c:48
AVFormatContext
Format I/O context.
Definition: avformat.h:1200
ttml_write_header
static int ttml_write_header(AVFormatContext *ctx)
Definition: ttmlenc.c:123
internal.h
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1095
TTMLHeaderParameters::pre_body_elements
const char * pre_body_elements
Definition: ttmlenc.c:44
NULL
#define NULL
Definition: coverity.c:32
write_trailer
static int write_trailer(AVFormatContext *s1)
Definition: v4l2enc.c:98
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:141
AVFormatContext::pb
AVIOContext * pb
I/O context.
Definition: avformat.h:1242
TTMLMuxContext::input_type
enum TTMLPacketType input_type
Definition: ttmlenc.c:48
AVStream::metadata
AVDictionary * metadata
Definition: avformat.h:1006
avio_w8
void avio_w8(AVIOContext *s, int b)
Definition: aviobuf.c:210
AVCodecParameters::extradata_size
int extradata_size
Size of the extradata content in bytes.
Definition: codec_par.h:78
AVFormatContext::nb_streams
unsigned int nb_streams
Number of elements in AVFormatContext.streams.
Definition: avformat.h:1256
AVIOContext
Bytestream IO Context.
Definition: avio.h:161
AVPacket::size
int size
Definition: packet.h:374
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:117
TTMLMuxContext::document_written
unsigned int document_written
Definition: ttmlenc.c:49
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:39
avio_write
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:232
ttml_set_header_values_from_extradata
static int ttml_set_header_values_from_extradata(AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
Definition: ttmlenc.c:81
write_packet
static void write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int unqueue)
Definition: ffmpeg.c:727
AVFMT_GLOBALHEADER
#define AVFMT_GLOBALHEADER
Format wants global header.
Definition: avformat.h:474
AVOutputFormat
Definition: avformat.h:503
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:366
internal.h
AV_CODEC_ID_TTML
@ AV_CODEC_ID_TTML
Definition: codec_id.h:546
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:485
tag
uint32_t tag
Definition: movenc.c:1596
ret
ret
Definition: filter_design.txt:187
AVStream
Stream structure.
Definition: avformat.h:935
ff_ttml_muxer
const AVOutputFormat ff_ttml_muxer
Definition: ttmlenc.c:218
avformat.h
avio_printf
int avio_printf(AVIOContext *s, const char *fmt,...) av_printf_format(2
Writes a formatted string to the context.
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: utils.c:1196
ttml_default_namespacing
static const char ttml_default_namespacing[]
Definition: ttmlenc.h:28
ttmlenc.h
AVDictionaryEntry
Definition: dict.h:79
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:60
AVPacket
This structure stores compressed data.
Definition: packet.h:350
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
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:28
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
AVDictionaryEntry::value
char * value
Definition: dict.h:81
avstring.h
write_header
static void write_header(FFV1Context *f)
Definition: ffv1enc.c:347
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:1228
min
float min
Definition: vorbis_enc_data.h:429
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