libavformat/sdp.c

   1 /*
   2  * copyright (c) 2007 Luca Abeni
   3  *
   4  * This file is part of Libav.
   5  *
   6  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include <string.h>
  22 #include "libavutil/avstring.h"
  23 #include "libavutil/base64.h"
  24 #include "libavutil/dict.h"
  25 #include "libavutil/parseutils.h"
  26 #include "libavutil/opt.h"
  27 #include "libavcodec/xiph.h"
  28 #include "libavcodec/mpeg4audio.h"
  29 #include "avformat.h"
  30 #include "internal.h"
  31 #include "avc.h"
  32 #include "rtp.h"
  33 #if CONFIG_NETWORK
  34 #include "network.h"
  35 #endif
  36
  37 #if CONFIG_RTP_MUXER
  38 #define MAX_EXTRADATA_SIZE ((INT_MAX - 10) / 2)
  39
  40 struct sdp_session_level {
  41     int sdp_version;      /**< protocol version (currently 0) */
  42     int id;               /**< session ID */
  43     int version;          /**< session version */
  44     int start_time;       /**< session start time (NTP time, in seconds),
  45                                or 0 in case of permanent session */
  46     int end_time;         /**< session end time (NTP time, in seconds),
  47                                or 0 if the session is not bounded */
  48     int ttl;              /**< TTL, in case of multicast stream */
  49     const char *user;     /**< username of the session's creator */
  50     const char *src_addr; /**< IP address of the machine from which the session was created */
  51     const char *src_type; /**< address type of src_addr */
  52     const char *dst_addr; /**< destination IP address (can be multicast) */
  53     const char *dst_type; /**< destination IP address type */
  54     const char *name;     /**< session name (can be an empty string) */
  55 };
  56
  57 static void sdp_write_address(char *buff, int size, const char *dest_addr,
  58                               const char *dest_type, int ttl)
  59 {
  60     if (dest_addr) {
  61         if (!dest_type)
  62             dest_type = "IP4";
  63         if (ttl > 0 && !strcmp(dest_type, "IP4")) {
  64             /* The TTL should only be specified for IPv4 multicast addresses,
  65              * not for IPv6. */
  66             av_strlcatf(buff, size, "c=IN %s %s/%d\r\n", dest_type, dest_addr, ttl);
  67         } else {
  68             av_strlcatf(buff, size, "c=IN %s %s\r\n", dest_type, dest_addr);
  69         }
  70     }
  71 }
  72
  73 static void sdp_write_header(char *buff, int size, struct sdp_session_level *s)
  74 {
  75     av_strlcatf(buff, size, "v=%d\r\n"
  76                             "o=- %d %d IN %s %s\r\n"
  77                             "s=%s\r\n",
  78                             s->sdp_version,
  79                             s->id, s->version, s->src_type, s->src_addr,
  80                             s->name);
  81     sdp_write_address(buff, size, s->dst_addr, s->dst_type, s->ttl);
  82     av_strlcatf(buff, size, "t=%d %d\r\n"
  83                             "a=tool:libavformat " AV_STRINGIFY(LIBAVFORMAT_VERSION) "\r\n",
  84                             s->start_time, s->end_time);
  85 }
  86
  87 #if CONFIG_NETWORK
  88 static int resolve_destination(char *dest_addr, int size, char *type,
  89                                int type_size)
  90 {
  91     struct addrinfo hints, *ai;
  92     int is_multicast;
  93
  94     av_strlcpy(type, "IP4", type_size);
  95     if (!dest_addr[0])
  96         return 0;
  97
  98     /* Resolve the destination, since it must be written
  99      * as a numeric IP address in the SDP. */
 100
 101     memset(&hints, 0, sizeof(hints));
 102     if (getaddrinfo(dest_addr, NULL, &hints, &ai))
 103         return 0;
 104     getnameinfo(ai->ai_addr, ai->ai_addrlen, dest_addr, size,
 105                 NULL, 0, NI_NUMERICHOST);
 106 #ifdef AF_INET6
 107     if (ai->ai_family == AF_INET6)
 108         av_strlcpy(type, "IP6", type_size);
 109 #endif
 110     is_multicast = ff_is_multicast_address(ai->ai_addr);
 111     freeaddrinfo(ai);
 112     return is_multicast;
 113 }
 114 #else
 115 static int resolve_destination(char *dest_addr, int size, char *type,
 116                                int type_size)
 117 {
 118     return 0;
 119 }
 120 #endif
 121
 122 static int sdp_get_address(char *dest_addr, int size, int *ttl, const char *url)
 123 {
 124     int port;
 125     const char *p;
 126     char proto[32];
 127
 128     av_url_split(proto, sizeof(proto), NULL, 0, dest_addr, size, &port, NULL, 0, url);
 129
 130     *ttl = 0;
 131
 132     if (strcmp(proto, "rtp")) {
 133         /* The url isn't for the actual rtp sessions,
 134          * don't parse out anything else than the destination.
 135          */
 136         return 0;
 137     }
 138
 139     p = strchr(url, '?');
 140     if (p) {
 141         char buff[64];
 142
 143         if (av_find_info_tag(buff, sizeof(buff), "ttl", p)) {
 144             *ttl = strtol(buff, NULL, 10);
 145         } else {
 146             *ttl = 5;
 147         }
 148     }
 149
 150     return port;
 151 }
 152
 153 #define MAX_PSET_SIZE 1024
 154 static char *extradata2psets(AVCodecContext *c)
 155 {
 156     char *psets, *p;
 157     const uint8_t *r;
 158     const char *pset_string = "; sprop-parameter-sets=";
 159
 160     if (c->extradata_size > MAX_EXTRADATA_SIZE) {
 161         av_log(c, AV_LOG_ERROR, "Too much extradata!\n");
 162
 163         return NULL;
 164     }
 165     if (c->extradata[0] == 1) {
 166         uint8_t *dummy_p;
 167         int dummy_int;
 168         AVBitStreamFilterContext *bsfc= av_bitstream_filter_init("h264_mp4toannexb");
 169
 170         if (!bsfc) {
 171             av_log(c, AV_LOG_ERROR, "Cannot open the h264_mp4toannexb BSF!\n");
 172
 173             return NULL;
 174         }
 175         av_bitstream_filter_filter(bsfc, c, NULL, &dummy_p, &dummy_int, NULL, 0, 0);
 176         av_bitstream_filter_close(bsfc);
 177     }
 178
 179     psets = av_mallocz(MAX_PSET_SIZE);
 180     if (psets == NULL) {
 181         av_log(c, AV_LOG_ERROR, "Cannot allocate memory for the parameter sets.\n");
 182         return NULL;
 183     }
 184     memcpy(psets, pset_string, strlen(pset_string));
 185     p = psets + strlen(pset_string);
 186     r = ff_avc_find_startcode(c->extradata, c->extradata + c->extradata_size);
 187     while (r < c->extradata + c->extradata_size) {
 188         const uint8_t *r1;
 189         uint8_t nal_type;
 190
 191         while (!*(r++));
 192         nal_type = *r & 0x1f;
 193         r1 = ff_avc_find_startcode(r, c->extradata + c->extradata_size);
 194         if (nal_type != 7 && nal_type != 8) { /* Only output SPS and PPS */
 195             r = r1;
 196             continue;
 197         }
 198         if (p != (psets + strlen(pset_string))) {
 199             *p = ',';
 200             p++;
 201         }
 202         if (av_base64_encode(p, MAX_PSET_SIZE - (p - psets), r, r1 - r) == NULL) {
 203             av_log(c, AV_LOG_ERROR, "Cannot Base64-encode %td %td!\n", MAX_PSET_SIZE - (p - psets), r1 - r);
 204             av_free(psets);
 205
 206             return NULL;
 207         }
 208         p += strlen(p);
 209         r = r1;
 210     }
 211
 212     return psets;
 213 }
 214
 215 static char *extradata2config(AVCodecContext *c)
 216 {
 217     char *config;
 218
 219     if (c->extradata_size > MAX_EXTRADATA_SIZE) {
 220         av_log(c, AV_LOG_ERROR, "Too much extradata!\n");
 221
 222         return NULL;
 223     }
 224     config = av_malloc(10 + c->extradata_size * 2);
 225     if (config == NULL) {
 226         av_log(c, AV_LOG_ERROR, "Cannot allocate memory for the config info.\n");
 227         return NULL;
 228     }
 229     memcpy(config, "; config=", 9);
 230     ff_data_to_hex(config + 9, c->extradata, c->extradata_size, 0);
 231     config[9 + c->extradata_size * 2] = 0;
 232
 233     return config;
 234 }
 235
 236 static char *xiph_extradata2config(AVCodecContext *c)
 237 {
 238     char *config, *encoded_config;
 239     uint8_t *header_start[3];
 240     int headers_len, header_len[3], config_len;
 241     int first_header_size;
 242
 243     switch (c->codec_id) {
 244     case CODEC_ID_THEORA:
 245         first_header_size = 42;
 246         break;
 247     case CODEC_ID_VORBIS:
 248         first_header_size = 30;
 249         break;
 250     default:
 251         av_log(c, AV_LOG_ERROR, "Unsupported Xiph codec ID\n");
 252         return NULL;
 253     }
 254
 255     if (avpriv_split_xiph_headers(c->extradata, c->extradata_size,
 256                               first_header_size, header_start,
 257                               header_len) < 0) {
 258         av_log(c, AV_LOG_ERROR, "Extradata corrupt.\n");
 259         return NULL;
 260     }
 261
 262     headers_len = header_len[0] + header_len[2];
 263     config_len = 4 +          // count
 264                  3 +          // ident
 265                  2 +          // packet size
 266                  1 +          // header count
 267                  2 +          // header size
 268                  headers_len; // and the rest
 269
 270     config = av_malloc(config_len);
 271     if (!config)
 272         goto xiph_fail;
 273
 274     encoded_config = av_malloc(AV_BASE64_SIZE(config_len));
 275     if (!encoded_config) {
 276         av_free(config);
 277         goto xiph_fail;
 278     }
 279
 280     config[0] = config[1] = config[2] = 0;
 281     config[3] = 1;
 282     config[4] = (RTP_XIPH_IDENT >> 16) & 0xff;
 283     config[5] = (RTP_XIPH_IDENT >>  8) & 0xff;
 284     config[6] = (RTP_XIPH_IDENT      ) & 0xff;
 285     config[7] = (headers_len >> 8) & 0xff;
 286     config[8] = headers_len & 0xff;
 287     config[9] = 2;
 288     config[10] = header_len[0];
 289     config[11] = 0; // size of comment header; nonexistent
 290     memcpy(config + 12, header_start[0], header_len[0]);
 291     memcpy(config + 12 + header_len[0], header_start[2], header_len[2]);
 292
 293     av_base64_encode(encoded_config, AV_BASE64_SIZE(config_len),
 294                      config, config_len);
 295     av_free(config);
 296
 297     return encoded_config;
 298
 299 xiph_fail:
 300     av_log(c, AV_LOG_ERROR,
 301            "Not enough memory for configuration string\n");
 302     return NULL;
 303 }
 304
 305 static int latm_context2profilelevel(AVCodecContext *c)
 306 {
 307     /* MP4A-LATM
 308      * The RTP payload format specification is described in RFC 3016
 309      * The encoding specifications are provided in ISO/IEC 14496-3 */
 310
 311     int profile_level = 0x2B;
 312
 313     /* TODO: AAC Profile only supports AAC LC Object Type.
 314      * Different Object Types should implement different Profile Levels */
 315
 316     if (c->sample_rate <= 24000) {
 317         if (c->channels <= 2)
 318             profile_level = 0x28; // AAC Profile, Level 1
 319     } else if (c->sample_rate <= 48000) {
 320         if (c->channels <= 2) {
 321             profile_level = 0x29; // AAC Profile, Level 2
 322         } else if (c->channels <= 5) {
 323             profile_level = 0x2A; // AAC Profile, Level 4
 324         }
 325     } else if (c->sample_rate <= 96000) {
 326         if (c->channels <= 5) {
 327             profile_level = 0x2B; // AAC Profile, Level 5
 328         }
 329     }
 330
 331     return profile_level;
 332 }
 333
 334 static char *latm_context2config(AVCodecContext *c)
 335 {
 336     /* MP4A-LATM
 337      * The RTP payload format specification is described in RFC 3016
 338      * The encoding specifications are provided in ISO/IEC 14496-3 */
 339
 340     uint8_t config_byte[6];
 341     int rate_index;
 342     char *config;
 343
 344     for (rate_index = 0; rate_index < 16; rate_index++)
 345         if (avpriv_mpeg4audio_sample_rates[rate_index] == c->sample_rate)
 346             break;
 347     if (rate_index == 16) {
 348         av_log(c, AV_LOG_ERROR, "Unsupported sample rate\n");
 349         return NULL;
 350     }
 351
 352     config_byte[0] = 0x40;
 353     config_byte[1] = 0;
 354     config_byte[2] = 0x20 | rate_index;
 355     config_byte[3] = c->channels << 4;
 356     config_byte[4] = 0x3f;
 357     config_byte[5] = 0xc0;
 358
 359     config = av_malloc(6*2+1);
 360     if (!config) {
 361         av_log(c, AV_LOG_ERROR, "Cannot allocate memory for the config info.\n");
 362         return NULL;
 363     }
 364     ff_data_to_hex(config, config_byte, 6, 1);
 365     config[12] = 0;
 366
 367     return config;
 368 }
 369
 370 static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c, int payload_type, AVFormatContext *fmt)
 371 {
 372     char *config = NULL;
 373
 374     switch (c->codec_id) {
 375         case CODEC_ID_H264:
 376             if (c->extradata_size) {
 377                 config = extradata2psets(c);
 378             }
 379             av_strlcatf(buff, size, "a=rtpmap:%d H264/90000\r\n"
 380                                     "a=fmtp:%d packetization-mode=1%s\r\n",
 381                                      payload_type,
 382                                      payload_type, config ? config : "");
 383             break;
 384         case CODEC_ID_H263:
 385         case CODEC_ID_H263P:
 386             /* a=framesize is required by 3GPP TS 26.234 (PSS). It
 387              * actually specifies the maximum video size, but we only know
 388              * the current size. This is required for playback on Android
 389              * stagefright and on Samsung bada. */
 390             av_strlcatf(buff, size, "a=rtpmap:%d H263-2000/90000\r\n"
 391                                     "a=framesize:%d %d-%d\r\n",
 392                                     payload_type,
 393                                     payload_type, c->width, c->height);
 394             break;
 395         case CODEC_ID_MPEG4:
 396             if (c->extradata_size) {
 397                 config = extradata2config(c);
 398             }
 399             av_strlcatf(buff, size, "a=rtpmap:%d MP4V-ES/90000\r\n"
 400                                     "a=fmtp:%d profile-level-id=1%s\r\n",
 401                                      payload_type,
 402                                      payload_type, config ? config : "");
 403             break;
 404         case CODEC_ID_AAC:
 405             if (fmt && fmt->oformat->priv_class &&
 406                 av_opt_flag_is_set(fmt->priv_data, "rtpflags", "latm")) {
 407                 config = latm_context2config(c);
 408                 if (!config)
 409                     return NULL;
 410                 av_strlcatf(buff, size, "a=rtpmap:%d MP4A-LATM/%d/%d\r\n"
 411                                         "a=fmtp:%d profile-level-id=%d;cpresent=0;config=%s\r\n",
 412                                          payload_type, c->sample_rate, c->channels,
 413                                          payload_type, latm_context2profilelevel(c), config);
 414             } else {
 415                 if (c->extradata_size) {
 416                     config = extradata2config(c);
 417                 } else {
 418                     /* FIXME: maybe we can forge config information based on the
 419                      *        codec parameters...
 420                      */
 421                     av_log(c, AV_LOG_ERROR, "AAC with no global headers is currently not supported.\n");
 422                     return NULL;
 423                 }
 424                 if (config == NULL) {
 425                     return NULL;
 426                 }
 427                 av_strlcatf(buff, size, "a=rtpmap:%d MPEG4-GENERIC/%d/%d\r\n"
 428                                         "a=fmtp:%d profile-level-id=1;"
 429                                         "mode=AAC-hbr;sizelength=13;indexlength=3;"
 430                                         "indexdeltalength=3%s\r\n",
 431                                          payload_type, c->sample_rate, c->channels,
 432                                          payload_type, config);
 433             }
 434             break;
 435         case CODEC_ID_PCM_S16BE:
 436             if (payload_type >= RTP_PT_PRIVATE)
 437                 av_strlcatf(buff, size, "a=rtpmap:%d L16/%d/%d\r\n",
 438                                          payload_type,
 439                                          c->sample_rate, c->channels);
 440             break;
 441         case CODEC_ID_PCM_MULAW:
 442             if (payload_type >= RTP_PT_PRIVATE)
 443                 av_strlcatf(buff, size, "a=rtpmap:%d PCMU/%d/%d\r\n",
 444                                          payload_type,
 445                                          c->sample_rate, c->channels);
 446             break;
 447         case CODEC_ID_PCM_ALAW:
 448             if (payload_type >= RTP_PT_PRIVATE)
 449                 av_strlcatf(buff, size, "a=rtpmap:%d PCMA/%d/%d\r\n",
 450                                          payload_type,
 451                                          c->sample_rate, c->channels);
 452             break;
 453         case CODEC_ID_AMR_NB:
 454             av_strlcatf(buff, size, "a=rtpmap:%d AMR/%d/%d\r\n"
 455                                     "a=fmtp:%d octet-align=1\r\n",
 456                                      payload_type, c->sample_rate, c->channels,
 457                                      payload_type);
 458             break;
 459         case CODEC_ID_AMR_WB:
 460             av_strlcatf(buff, size, "a=rtpmap:%d AMR-WB/%d/%d\r\n"
 461                                     "a=fmtp:%d octet-align=1\r\n",
 462                                      payload_type, c->sample_rate, c->channels,
 463                                      payload_type);
 464             break;
 465         case CODEC_ID_VORBIS:
 466             if (c->extradata_size)
 467                 config = xiph_extradata2config(c);
 468             else
 469                 av_log(c, AV_LOG_ERROR, "Vorbis configuration info missing\n");
 470             if (!config)
 471                 return NULL;
 472
 473             av_strlcatf(buff, size, "a=rtpmap:%d vorbis/%d/%d\r\n"
 474                                     "a=fmtp:%d configuration=%s\r\n",
 475                                     payload_type, c->sample_rate, c->channels,
 476                                     payload_type, config);
 477             break;
 478         case CODEC_ID_THEORA: {
 479             const char *pix_fmt;
 480             if (c->extradata_size)
 481                 config = xiph_extradata2config(c);
 482             else
 483                 av_log(c, AV_LOG_ERROR, "Theora configuation info missing\n");
 484             if (!config)
 485                 return NULL;
 486
 487             switch (c->pix_fmt) {
 488             case PIX_FMT_YUV420P:
 489                 pix_fmt = "YCbCr-4:2:0";
 490                 break;
 491             case PIX_FMT_YUV422P:
 492                 pix_fmt = "YCbCr-4:2:2";
 493                 break;
 494             case PIX_FMT_YUV444P:
 495                 pix_fmt = "YCbCr-4:4:4";
 496                 break;
 497             default:
 498                 av_log(c, AV_LOG_ERROR, "Unsupported pixel format.\n");
 499                 return NULL;
 500             }
 501
 502             av_strlcatf(buff, size, "a=rtpmap:%d theora/90000\r\n"
 503                                     "a=fmtp:%d delivery-method=inline; "
 504                                     "width=%d; height=%d; sampling=%s; "
 505                                     "configuration=%s\r\n",
 506                                     payload_type, payload_type,
 507                                     c->width, c->height, pix_fmt, config);
 508             break;
 509         }
 510         case CODEC_ID_VP8:
 511             av_strlcatf(buff, size, "a=rtpmap:%d VP8/90000\r\n",
 512                                      payload_type);
 513             break;
 514         case CODEC_ID_ADPCM_G722:
 515             if (payload_type >= RTP_PT_PRIVATE)
 516                 av_strlcatf(buff, size, "a=rtpmap:%d G722/%d/%d\r\n",
 517                                          payload_type,
 518                                          8000, c->channels);
 519             break;
 520         case CODEC_ID_ADPCM_G726: {
 521             if (payload_type >= RTP_PT_PRIVATE)
 522                 av_strlcatf(buff, size, "a=rtpmap:%d G726-%d/%d\r\n",
 523                                          payload_type,
 524                                          c->bits_per_coded_sample*8,
 525                                          c->sample_rate);
 526             break;
 527         }
 528         default:
 529             /* Nothing special to do here... */
 530             break;
 531     }
 532
 533     av_free(config);
 534
 535     return buff;
 536 }
 537
 538 void ff_sdp_write_media(char *buff, int size, AVCodecContext *c, const char *dest_addr, const char *dest_type, int port, int ttl, AVFormatContext *fmt)
 539 {
 540     const char *type;
 541     int payload_type;
 542
 543     payload_type = ff_rtp_get_payload_type(fmt, c);
 544
 545     switch (c->codec_type) {
 546         case AVMEDIA_TYPE_VIDEO   : type = "video"      ; break;
 547         case AVMEDIA_TYPE_AUDIO   : type = "audio"      ; break;
 548         case AVMEDIA_TYPE_SUBTITLE: type = "text"       ; break;
 549         default                 : type = "application"; break;
 550     }
 551
 552     av_strlcatf(buff, size, "m=%s %d RTP/AVP %d\r\n", type, port, payload_type);
 553     sdp_write_address(buff, size, dest_addr, dest_type, ttl);
 554     if (c->bit_rate) {
 555         av_strlcatf(buff, size, "b=AS:%d\r\n", c->bit_rate / 1000);
 556     }
 557
 558     sdp_write_media_attributes(buff, size, c, payload_type, fmt);
 559 }
 560
 561 int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size)
 562 {
 563     AVDictionaryEntry *title = av_dict_get(ac[0]->metadata, "title", NULL, 0);
 564     struct sdp_session_level s;
 565     int i, j, port, ttl, is_multicast;
 566     char dst[32], dst_type[5];
 567
 568     memset(buf, 0, size);
 569     memset(&s, 0, sizeof(struct sdp_session_level));
 570     s.user = "-";
 571     s.src_addr = "127.0.0.1";    /* FIXME: Properly set this */
 572     s.src_type = "IP4";
 573     s.name = title ? title->value : "No Name";
 574
 575     port = 0;
 576     ttl = 0;
 577     if (n_files == 1) {
 578         port = sdp_get_address(dst, sizeof(dst), &ttl, ac[0]->filename);
 579         is_multicast = resolve_destination(dst, sizeof(dst), dst_type,
 580                                            sizeof(dst_type));
 581         if (!is_multicast)
 582             ttl = 0;
 583         if (dst[0]) {
 584             s.dst_addr = dst;
 585             s.dst_type = dst_type;
 586             s.ttl = ttl;
 587             if (!strcmp(dst_type, "IP6")) {
 588                 s.src_addr = "::1";
 589                 s.src_type = "IP6";
 590             }
 591         }
 592     }
 593     sdp_write_header(buf, size, &s);
 594
 595     dst[0] = 0;
 596     for (i = 0; i < n_files; i++) {
 597         if (n_files != 1) {
 598             port = sdp_get_address(dst, sizeof(dst), &ttl, ac[i]->filename);
 599             is_multicast = resolve_destination(dst, sizeof(dst), dst_type,
 600                                                sizeof(dst_type));
 601             if (!is_multicast)
 602                 ttl = 0;
 603         }
 604         for (j = 0; j < ac[i]->nb_streams; j++) {
 605             ff_sdp_write_media(buf, size,
 606                                   ac[i]->streams[j]->codec, dst[0] ? dst : NULL,
 607                                   dst_type, (port > 0) ? port + j * 2 : 0, ttl,
 608                                   ac[i]);
 609             if (port <= 0) {
 610                 av_strlcatf(buf, size,
 611                                    "a=control:streamid=%d\r\n", i + j);
 612             }
 613         }
 614     }
 615
 616     return 0;
 617 }
 618 #else
 619 int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size)
 620 {
 621     return AVERROR(ENOSYS);
 622 }
 623
 624 void ff_sdp_write_media(char *buff, int size, AVCodecContext *c, const char *dest_addr, const char *dest_type, int port, int ttl, AVFormatContext *fmt)
 625 {
 626 }
 627 #endif
 628
 629 #if FF_API_SDP_CREATE
 630 int avf_sdp_create(AVFormatContext *ac[], int n_files, char *buff, int size)
 631 {
 632     return av_sdp_create(ac, n_files, buff, size);
 633 }
 634 #endif