FFmpeg
webvttenc.c
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1 /*
2  * Copyright (c) 2013 Matthew Heaney
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * WebVTT subtitle muxer
24  * @see http://dev.w3.org/html5/webvtt/
25  */
26 
27 #include "avformat.h"
28 #include "internal.h"
29 
30 static void webvtt_write_time(AVIOContext *pb, int64_t millisec)
31 {
32  int64_t sec, min, hour;
33  sec = millisec / 1000;
34  millisec -= 1000 * sec;
35  min = sec / 60;
36  sec -= 60 * min;
37  hour = min / 60;
38  min -= 60 * hour;
39 
40  if (hour > 0)
41  avio_printf(pb, "%02"PRId64":", hour);
42 
43  avio_printf(pb, "%02"PRId64":%02"PRId64".%03"PRId64"", min, sec, millisec);
44 }
45 
47 {
48  AVStream *s = ctx->streams[0];
49  AVCodecParameters *par = ctx->streams[0]->codecpar;
50  AVIOContext *pb = ctx->pb;
51 
52  if (ctx->nb_streams != 1 || par->codec_id != AV_CODEC_ID_WEBVTT) {
53  av_log(ctx, AV_LOG_ERROR, "Exactly one WebVTT stream is needed.\n");
54  return AVERROR(EINVAL);
55  }
56 
57  avpriv_set_pts_info(s, 64, 1, 1000);
58 
59  avio_printf(pb, "WEBVTT\n");
60  avio_flush(pb);
61 
62  return 0;
63 }
64 
66 {
67  AVIOContext *pb = ctx->pb;
68  int id_size, settings_size;
69  uint8_t *id, *settings;
70 
71  avio_printf(pb, "\n");
72 
74  &id_size);
75 
76  if (id && id_size > 0)
77  avio_printf(pb, "%.*s\n", id_size, id);
78 
79  webvtt_write_time(pb, pkt->pts);
80  avio_printf(pb, " --> ");
81  webvtt_write_time(pb, pkt->pts + pkt->duration);
82 
84  &settings_size);
85 
86  if (settings && settings_size > 0)
87  avio_printf(pb, " %.*s", settings_size, settings);
88 
89  avio_printf(pb, "\n");
90 
91  avio_write(pb, pkt->data, pkt->size);
92  avio_printf(pb, "\n");
93 
94  return 0;
95 }
96 
98  .name = "webvtt",
99  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
100  .extensions = "vtt",
101  .mime_type = "text/vtt",
103  .subtitle_codec = AV_CODEC_ID_WEBVTT,
104  .write_header = webvtt_write_header,
105  .write_packet = webvtt_write_packet,
106 };
Bytestream IO Context.
Definition: avio.h:161
static int webvtt_write_header(AVFormatContext *ctx)
Definition: webvttenc.c:46
The optional first identifier line of a WebVTT cue.
Definition: avcodec.h:1340
void avpriv_set_pts_info(AVStream *s, 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:4892
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3957
int size
Definition: avcodec.h:1478
static AVPacket pkt
#define AVFMT_TS_NONSTRICT
Format does not require strictly increasing timestamps, but they must still be monotonic.
Definition: avformat.h:477
This struct describes the properties of an encoded stream.
Definition: avcodec.h:3949
Format I/O context.
Definition: avformat.h:1358
uint8_t
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: avcodec.h:1495
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1426
uint8_t * data
Definition: avcodec.h:1477
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:218
#define av_log(a,...)
static void webvtt_write_time(AVIOContext *pb, int64_t millisec)
Definition: webvttenc.c:30
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
AVOutputFormat ff_webvtt_muxer
Definition: webvttenc.c:97
uint8_t * av_packet_get_side_data(const AVPacket *pkt, enum AVPacketSideDataType type, int *size)
Get side information from packet.
Definition: avpacket.c:350
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
unsigned int nb_streams
Number of elements in AVFormatContext.streams.
Definition: avformat.h:1414
const char * name
Definition: avformat.h:505
AVFormatContext * ctx
Definition: movenc.c:48
#define s(width, name)
Definition: cbs_vp9.c:257
static int webvtt_write_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: webvttenc.c:65
Stream structure.
Definition: avformat.h:881
AVIOContext * pb
I/O context.
Definition: avformat.h:1400
void avio_flush(AVIOContext *s)
Force flushing of buffered data.
Definition: aviobuf.c:238
Main libavformat public API header.
The optional settings (rendering instructions) that immediately follow the timestamp specifier of a W...
Definition: avcodec.h:1346
#define AVFMT_VARIABLE_FPS
Format allows variable fps.
Definition: avformat.h:470
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1028
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
float min
enum AVCodecID id
This structure stores compressed data.
Definition: avcodec.h:1454
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:1470
int avio_printf(AVIOContext *s, const char *fmt,...) av_printf_format(2
Writes a formatted string to the context.