libavformat/dash.c

   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/avstring.h"
  28 #include "libavutil/intreadwrite.h"
  29 #include "libavutil/mathematics.h"
  30 #include "libavutil/opt.h"
  31 #include "libavutil/rational.h"
  32 #include "libavutil/time_internal.h"
  33
  34 #include "avc.h"
  35 #include "avformat.h"
  36 #include "avio_internal.h"
  37 #include "internal.h"
  38 #include "isom.h"
  39 #include "os_support.h"
  40 #include "url.h"
  41 #include "dash.h"
  42
  43 static DASHTmplId dash_read_tmpl_id(const char *identifier, char *format_tag,
  44                                     size_t format_tag_size, const char **ptr) {
  45     const char *next_ptr;
  46     DASHTmplId id_type = DASH_TMPL_ID_UNDEFINED;
  47
  48     if (av_strstart(identifier, "$$", &next_ptr)) {
  49         id_type = DASH_TMPL_ID_ESCAPE;
  50         *ptr = next_ptr;
  51     } else if (av_strstart(identifier, "$RepresentationID$", &next_ptr)) {
  52         id_type = DASH_TMPL_ID_REP_ID;
  53         // default to basic format, as $RepresentationID$ identifiers
  54         // are not allowed to have custom format-tags.
  55         av_strlcpy(format_tag, "%d", format_tag_size);
  56         *ptr = next_ptr;
  57     } else { // the following identifiers may have an explicit format_tag
  58         if (av_strstart(identifier, "$Number", &next_ptr))
  59             id_type = DASH_TMPL_ID_NUMBER;
  60         else if (av_strstart(identifier, "$Bandwidth", &next_ptr))
  61             id_type = DASH_TMPL_ID_BANDWIDTH;
  62         else if (av_strstart(identifier, "$Time", &next_ptr))
  63             id_type = DASH_TMPL_ID_TIME;
  64         else
  65             id_type = DASH_TMPL_ID_UNDEFINED;
  66
  67         // next parse the dash format-tag and generate a c-string format tag
  68         // (next_ptr now points at the first '%' at the beginning of the format-tag)
  69         if (id_type != DASH_TMPL_ID_UNDEFINED) {
  70             const char *number_format = (id_type == DASH_TMPL_ID_TIME) ? PRId64 : "d";
  71             if (next_ptr[0] == '$') { // no dash format-tag
  72                 snprintf(format_tag, format_tag_size, "%%%s", number_format);
  73                 *ptr = &next_ptr[1];
  74             } else {
  75                 const char *width_ptr;
  76                 // only tolerate single-digit width-field (i.e. up to 9-digit width)
  77                 if (av_strstart(next_ptr, "%0", &width_ptr) &&
  78                     av_isdigit(width_ptr[0]) &&
  79                     av_strstart(&width_ptr[1], "d$", &next_ptr)) {
  80                     // yes, we're using a format tag to build format_tag.
  81                     snprintf(format_tag, format_tag_size, "%s%c%s", "%0", width_ptr[0], number_format);
  82                     *ptr = next_ptr;
  83                 } else {
  84                     av_log(NULL, AV_LOG_WARNING, "Failed to parse format-tag beginning with %s. Expected either a "
  85                                                  "closing '$' character or a format-string like '%%0[width]d', "
  86                                                  "where width must be a single digit\n", next_ptr);
  87                     id_type = DASH_TMPL_ID_UNDEFINED;
  88                 }
  89             }
  90         }
  91     }
  92     return id_type;
  93 }
  94
  95 void ff_dash_fill_tmpl_params(char *dst, size_t buffer_size,
  96                                   const char *template, int rep_id,
  97                                   int number, int bit_rate,
  98                                   int64_t time) {
  99     int dst_pos = 0;
 100     const char *t_cur = template;
 101     while (dst_pos < buffer_size - 1 && *t_cur) {
 102         char format_tag[7]; // May be "%d", "%0Xd", or "%0Xlld" (for $Time$), where X is in [0-9]
 103         int n = 0;
 104         DASHTmplId id_type;
 105         const char *t_next = strchr(t_cur, '$'); // copy over everything up to the first '$' character
 106         if (t_next) {
 107             int num_copy_bytes = FFMIN(t_next - t_cur, buffer_size - dst_pos - 1);
 108             av_strlcpy(&dst[dst_pos], t_cur, num_copy_bytes + 1);
 109             // advance
 110             dst_pos += num_copy_bytes;
 111             t_cur = t_next;
 112         } else { // no more DASH identifiers to substitute - just copy the rest over and break
 113             av_strlcpy(&dst[dst_pos], t_cur, buffer_size - dst_pos);
 114             break;
 115         }
 116
 117         if (dst_pos >= buffer_size - 1 || !*t_cur)
 118             break;
 119
 120         // t_cur is now pointing to a '$' character
 121         id_type = dash_read_tmpl_id(t_cur, format_tag, sizeof(format_tag), &t_next);
 122         switch (id_type) {
 123         case DASH_TMPL_ID_ESCAPE:
 124             av_strlcpy(&dst[dst_pos], "$", 2);
 125             n = 1;
 126             break;
 127         case DASH_TMPL_ID_REP_ID:
 128             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, rep_id);
 129             break;
 130         case DASH_TMPL_ID_NUMBER:
 131             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, number);
 132             break;
 133         case DASH_TMPL_ID_BANDWIDTH:
 134             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, bit_rate);
 135             break;
 136         case DASH_TMPL_ID_TIME:
 137             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, time);
 138             break;
 139         case DASH_TMPL_ID_UNDEFINED:
 140             // copy over one byte and advance
 141             av_strlcpy(&dst[dst_pos], t_cur, 2);
 142             n = 1;
 143             t_next = &t_cur[1];
 144             break;
 145         }
 146         // t_next points just past the processed identifier
 147         // n is the number of bytes that were attempted to be written to dst
 148         // (may have failed to write all because buffer_size).
 149
 150         // advance
 151         dst_pos += FFMIN(n, buffer_size - dst_pos - 1);
 152         t_cur = t_next;
 153     }
 154 }