FFmpeg
dash.c
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1 /*
2  * MPEG-DASH ISO BMFF segmenter
3  * Copyright (c) 2014 Martin Storsjo
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 #include "config.h"
23 #if HAVE_UNISTD_H
24 #include <unistd.h>
25 #endif
26 
27 #include "libavutil/avassert.h"
28 #include "libavutil/avstring.h"
29 #include "libavutil/intreadwrite.h"
30 #include "libavutil/mathematics.h"
31 #include "libavutil/opt.h"
32 #include "libavutil/rational.h"
34 
35 #include "avc.h"
36 #include "avformat.h"
37 #include "avio_internal.h"
38 #include "internal.h"
39 #include "isom.h"
40 #include "os_support.h"
41 #include "url.h"
42 #include "dash.h"
43 
44 static DASHTmplId dash_read_tmpl_id(const char *identifier, char *format_tag,
45  size_t format_tag_size, const char **ptr) {
46  const char *next_ptr;
48 
49  if (av_strstart(identifier, "$$", &next_ptr)) {
50  id_type = DASH_TMPL_ID_ESCAPE;
51  *ptr = next_ptr;
52  } else if (av_strstart(identifier, "$RepresentationID$", &next_ptr)) {
53  id_type = DASH_TMPL_ID_REP_ID;
54  // default to basic format, as $RepresentationID$ identifiers
55  // are not allowed to have custom format-tags.
56  av_strlcpy(format_tag, "%d", format_tag_size);
57  *ptr = next_ptr;
58  } else { // the following identifiers may have an explicit format_tag
59  if (av_strstart(identifier, "$Number", &next_ptr))
60  id_type = DASH_TMPL_ID_NUMBER;
61  else if (av_strstart(identifier, "$Bandwidth", &next_ptr))
62  id_type = DASH_TMPL_ID_BANDWIDTH;
63  else if (av_strstart(identifier, "$Time", &next_ptr))
64  id_type = DASH_TMPL_ID_TIME;
65  else
66  id_type = DASH_TMPL_ID_UNDEFINED;
67 
68  // next parse the dash format-tag and generate a c-string format tag
69  // (next_ptr now points at the first '%' at the beginning of the format-tag)
70  if (id_type != DASH_TMPL_ID_UNDEFINED) {
71  const char *number_format = (id_type == DASH_TMPL_ID_TIME) ? PRId64 : "d";
72  if (next_ptr[0] == '$') { // no dash format-tag
73  snprintf(format_tag, format_tag_size, "%%%s", number_format);
74  *ptr = &next_ptr[1];
75  } else {
76  const char *width_ptr;
77  // only tolerate single-digit width-field (i.e. up to 9-digit width)
78  if (av_strstart(next_ptr, "%0", &width_ptr) &&
79  av_isdigit(width_ptr[0]) &&
80  av_strstart(&width_ptr[1], "d$", &next_ptr)) {
81  // yes, we're using a format tag to build format_tag.
82  snprintf(format_tag, format_tag_size, "%s%c%s", "%0", width_ptr[0], number_format);
83  *ptr = next_ptr;
84  } else {
85  av_log(NULL, AV_LOG_WARNING, "Failed to parse format-tag beginning with %s. Expected either a "
86  "closing '$' character or a format-string like '%%0[width]d', "
87  "where width must be a single digit\n", next_ptr);
88  id_type = DASH_TMPL_ID_UNDEFINED;
89  }
90  }
91  }
92  }
93  return id_type;
94 }
95 
96 void ff_dash_fill_tmpl_params(char *dst, size_t buffer_size,
97  const char *template, int rep_id,
98  int number, int bit_rate,
99  int64_t time) {
100  int dst_pos = 0;
101  const char *t_cur = template;
102  while (dst_pos < buffer_size - 1 && *t_cur) {
103  char format_tag[7]; // May be "%d", "%0Xd", or "%0Xlld" (for $Time$), where X is in [0-9]
104  int n = 0;
105  DASHTmplId id_type;
106  const char *t_next = strchr(t_cur, '$'); // copy over everything up to the first '$' character
107  if (t_next) {
108  int num_copy_bytes = FFMIN(t_next - t_cur, buffer_size - dst_pos - 1);
109  av_strlcpy(&dst[dst_pos], t_cur, num_copy_bytes + 1);
110  // advance
111  dst_pos += num_copy_bytes;
112  t_cur = t_next;
113  } else { // no more DASH identifiers to substitute - just copy the rest over and break
114  av_strlcpy(&dst[dst_pos], t_cur, buffer_size - dst_pos);
115  break;
116  }
117 
118  if (dst_pos >= buffer_size - 1 || !*t_cur)
119  break;
120 
121  // t_cur is now pointing to a '$' character
122  id_type = dash_read_tmpl_id(t_cur, format_tag, sizeof(format_tag), &t_next);
123  switch (id_type) {
124  case DASH_TMPL_ID_ESCAPE:
125  av_strlcpy(&dst[dst_pos], "$", 2);
126  n = 1;
127  break;
128  case DASH_TMPL_ID_REP_ID:
129  n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, rep_id);
130  break;
131  case DASH_TMPL_ID_NUMBER:
132  n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, number);
133  break;
135  n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, bit_rate);
136  break;
137  case DASH_TMPL_ID_TIME:
138  n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, time);
139  break;
141  // copy over one byte and advance
142  av_strlcpy(&dst[dst_pos], t_cur, 2);
143  n = 1;
144  t_next = &t_cur[1];
145  break;
146  }
147  // t_next points just past the processed identifier
148  // n is the number of bytes that were attempted to be written to dst
149  // (may have failed to write all because buffer_size).
150 
151  // advance
152  dst_pos += FFMIN(n, buffer_size - dst_pos - 1);
153  t_cur = t_next;
154  }
155 }
156 
157 
#define NULL
Definition: coverity.c:32
static av_const int av_isdigit(int c)
Locale-independent conversion of ASCII isdigit.
Definition: avstring.h:206
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
AVOptions.
miscellaneous OS support macros and functions.
#define av_log(a,...)
static DASHTmplId dash_read_tmpl_id(const char *identifier, char *format_tag, size_t format_tag_size, const char **ptr)
Definition: dash.c:44
simple assert() macros that are a bit more flexible than ISO C assert().
size_t av_strlcpy(char *dst, const char *src, size_t size)
Copy the string src to dst, but no more than size - 1 bytes, and null-terminate dst.
Definition: avstring.c:83
#define FFMIN(a, b)
Definition: common.h:96
int n
Definition: avisynth_c.h:760
void ff_dash_fill_tmpl_params(char *dst, size_t buffer_size, const char *template, int rep_id, int number, int bit_rate, int64_t time)
Definition: dash.c:96
#define snprintf
Definition: snprintf.h:34
DASHTmplId
Definition: dash.h:27
int av_strstart(const char *str, const char *pfx, const char **ptr)
Return non-zero if pfx is a prefix of str.
Definition: avstring.c:34
Main libavformat public API header.
Utilties for rational number calculation.
unbuffered private I/O API