ffmpeg/libavformat/subtitles.h

   1 /*
   2  * Copyright (c) 2012 Clément Bœsch
   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 #ifndef AVFORMAT_SUBTITLES_H
  22 #define AVFORMAT_SUBTITLES_H
  23
  24 #include <stdint.h>
  25 #include <stddef.h>
  26 #include "avformat.h"
  27 #include "libavutil/bprint.h"
  28
  29 enum sub_sort {
  30     SUB_SORT_TS_POS = 0,    ///< sort by timestamps, then position
  31     SUB_SORT_POS_TS,        ///< sort by position, then timestamps
  32 };
  33
  34 enum ff_utf_type {
  35     FF_UTF_8,       // or other 8 bit encodings
  36     FF_UTF16LE,
  37     FF_UTF16BE,
  38 };
  39
  40 typedef struct {
  41     int type;
  42     AVIOContext *pb;
  43     unsigned char buf[8];
  44     int buf_pos, buf_len;
  45     AVIOContext buf_pb;
  46 } FFTextReader;
  47
  48 /**
  49  * Initialize the FFTextReader from the given AVIOContext. This function will
  50  * read some bytes from pb, and test for UTF-8 or UTF-16 BOMs. Further accesses
  51  * to FFTextReader will read more data from pb.
  52  * If s is not NULL, the user will be warned if a UTF-16 conversion takes place.
  53  *
  54  * The purpose of FFTextReader is to transparently convert read data to UTF-8
  55  * if the stream had a UTF-16 BOM.
  56  *
  57  * @param s Pointer to provide av_log context
  58  * @param r object which will be initialized
  59  * @param pb stream to read from (referenced as long as FFTextReader is in use)
  60  */
  61 void ff_text_init_avio(void *s, FFTextReader *r, AVIOContext *pb);
  62
  63 /**
  64  * Similar to ff_text_init_avio(), but sets it up to read from a bounded buffer.
  65  *
  66  * @param r object which will be initialized
  67  * @param buf buffer to read from (referenced as long as FFTextReader is in use)
  68  * @param size size of buf
  69  */
  70 void ff_text_init_buf(FFTextReader *r, void *buf, size_t size);
  71
  72 /**
  73  * Return the byte position of the next byte returned by ff_text_r8(). For
  74  * UTF-16 source streams, this will return the original position, but it will
  75  * be incorrect if a codepoint was only partially read with ff_text_r8().
  76  */
  77 int64_t ff_text_pos(FFTextReader *r);
  78
  79 /**
  80  * Return the next byte. The return value is always 0 - 255. Returns 0 on EOF.
  81  * If the source stream is UTF-16, this reads from the stream converted to
  82  * UTF-8. On invalid UTF-16, 0 is returned.
  83  */
  84 int ff_text_r8(FFTextReader *r);
  85
  86 /**
  87  * Return non-zero if EOF was reached.
  88  */
  89 int ff_text_eof(FFTextReader *r);
  90
  91 /**
  92  * Like ff_text_r8(), but don't remove the byte from the buffer.
  93  */
  94 int ff_text_peek_r8(FFTextReader *r);
  95
  96 /**
  97  * Read the given number of bytes (in UTF-8). On error or EOF, \0 bytes are
  98  * written.
  99  */
 100 void ff_text_read(FFTextReader *r, char *buf, size_t size);
 101
 102 typedef struct {
 103     AVPacket *subs;         ///< array of subtitles packets
 104     int nb_subs;            ///< number of subtitles packets
 105     int allocated_size;     ///< allocated size for subs
 106     int current_sub_idx;    ///< current position for the read packet callback
 107     enum sub_sort sort;     ///< sort method to use when finalizing subtitles
 108 } FFDemuxSubtitlesQueue;
 109
 110 /**
 111  * Insert a new subtitle event.
 112  *
 113  * @param event the subtitle line, may not be zero terminated
 114  * @param len   the length of the event (in strlen() sense, so without '\0')
 115  * @param merge set to 1 if the current event should be concatenated with the
 116  *              previous one instead of adding a new entry, 0 otherwise
 117  */
 118 AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
 119                                     const uint8_t *event, int len, int merge);
 120
 121 /**
 122  * Set missing durations and sort subtitles by PTS, and then byte position.
 123  */
 124 void ff_subtitles_queue_finalize(FFDemuxSubtitlesQueue *q);
 125
 126 /**
 127  * Generic read_packet() callback for subtitles demuxers using this queue
 128  * system.
 129  */
 130 int ff_subtitles_queue_read_packet(FFDemuxSubtitlesQueue *q, AVPacket *pkt);
 131
 132 /**
 133  * Update current_sub_idx to emulate a seek. Except the first parameter, it
 134  * matches AVInputFormat->read_seek2 prototypes.
 135  */
 136 int ff_subtitles_queue_seek(FFDemuxSubtitlesQueue *q, AVFormatContext *s, int stream_index,
 137                             int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
 138
 139 /**
 140  * Remove and destroy all the subtitles packets.
 141  */
 142 void ff_subtitles_queue_clean(FFDemuxSubtitlesQueue *q);
 143
 144 /**
 145  * SMIL helper to load next chunk ("<...>" or untagged content) in buf.
 146  *
 147  * @param c cached character, to avoid a backward seek
 148  */
 149 int ff_smil_extract_next_text_chunk(FFTextReader *tr, AVBPrint *buf, char *c);
 150
 151 /**
 152  * SMIL helper to point on the value of an attribute in the given tag.
 153  *
 154  * @param s    SMIL tag ("<...>")
 155  * @param attr the attribute to look for
 156  */
 157 const char *ff_smil_get_attr_ptr(const char *s, const char *attr);
 158
 159 /**
 160  * @brief Same as ff_subtitles_read_text_chunk(), but read from an AVIOContext.
 161  */
 162 void ff_subtitles_read_chunk(AVIOContext *pb, AVBPrint *buf);
 163
 164 /**
 165  * @brief Read a subtitles chunk from FFTextReader.
 166  *
 167  * A chunk is defined by a multiline "event", ending with a second line break.
 168  * The trailing line breaks are trimmed. CRLF are supported.
 169  * Example: "foo\r\nbar\r\n\r\nnext" will print "foo\r\nbar" into buf, and pb
 170  * will focus on the 'n' of the "next" string.
 171  *
 172  * @param tr  I/O context
 173  * @param buf an initialized buf where the chunk is written
 174  *
 175  * @note buf is cleared before writing into it.
 176  */
 177 void ff_subtitles_read_text_chunk(FFTextReader *tr, AVBPrint *buf);
 178
 179 /**
 180  * Get the number of characters to increment to jump to the next line, or to
 181  * the end of the string.
 182  * The function handles the following line breaks schemes:
 183  * LF, CRLF (MS), or standalone CR (old MacOS).
 184  */
 185 static av_always_inline int ff_subtitles_next_line(const char *ptr)
 186 {
 187     int n = strcspn(ptr, "\r\n");
 188     ptr += n;
 189     if (*ptr == '\r') {
 190         ptr++;
 191         n++;
 192     }
 193     if (*ptr == '\n')
 194         n++;
 195     return n;
 196 }
 197
 198 /**
 199  * Read a line of text. Discards line ending characters.
 200  * The function handles the following line breaks schemes:
 201  * LF, CRLF (MS), or standalone CR (old MacOS).
 202  *
 203  * Returns the number of bytes written to buf. Always writes a terminating 0,
 204  * similar as with snprintf.
 205  *
 206  * @note returns a negative error code if a \0 byte is found
 207  */
 208 ptrdiff_t ff_subtitles_read_line(FFTextReader *tr, char *buf, size_t size);
 209
 210 #endif /* AVFORMAT_SUBTITLES_H */