Introduce an SDP generator

Originally committed as revision 9806 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/Makefile

@@ -6,7 +6,7 @@ include ../config.mak
 
 CFLAGS+=-I$(SRC_PATH)/libavcodec
 
-OBJS= utils.o cutils.o os_support.o allformats.o
+OBJS= utils.o cutils.o os_support.o allformats.o sdp.o
 
 HEADERS = avformat.h avio.h rtp.h rtsp.h rtspcodes.h
 

libavformat/avformat.h

@@ -833,6 +833,21 @@ int av_get_frame_filename(char *buf, int buf_size,
  */
 int av_filename_number_test(const char *filename);
 
+/**
+ * Generate an SDP for an RTP session.
+ *
+ * @param ac array of AVFormatContexts describing the RTP streams. If the
+ *           array is composed by only one context, such context can contain
+ *           multiple AVStreams (one AVStream per RTP stream). Otherwise,
+ *           all the contexts in the array (an AVCodecContext per RTP stream)
+ *           must contain only one AVStream
+ * @param n_streams number of AVCodecContexts contained in ac
+ * @return a pointer to the SDP (an array of chars which is allocated by
+ *         avf_sdp_create(), and must be freed by the caller), or NULL in
+ *         case of failure.
+ */
+char *avf_sdp_create(AVFormatContext *ac[], int n_streams);
+
 #ifdef HAVE_AV_CONFIG_H
 
 #include "os_support.h"

libavformat/sdp.c

@@ -0,0 +1,217 @@
+/*
+ * copyright (c) 2007 Luca Abeni
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avstring.h"
+#include "avformat.h"
+
+#define MAX_EXTRADATA_SIZE ((INT_MAX - 10) / 2)
+
+struct sdp_session_level {
+    int sdp_version;      /**< protocol version (currently 0) */
+    int id;               /**< session id */
+    int version;          /**< session version */
+    int start_time;       /**< session start time (NTP time, in seconds),
+                             or 0 in case of permanent session */
+    int end_time;         /**< session end time (NTP time, in seconds),
+                               or 0 if the session is not bounded */
+    int ttl;              /**< TTL, in case of multicast stream */
+    const char *user;     /**< username of the session's creator */
+    const char *src_addr; /**< IP address of the machine from which the session was created */
+    const char *dst_addr; /**< destination IP address (can be multicast) */
+    const char *name;     /**< session name (can be an empty string) */
+};
+
+static void dest_write(char *buff, int size, const char *dest_addr, int ttl)
+{
+    if (dest_addr) {
+        if (ttl > 0) {
+            av_strlcatf(buff, size, "c=IN IP4 %s/%d\r\n", dest_addr, ttl);
+        } else {
+            av_strlcatf(buff, size, "c=IN IP4 %s\r\n", dest_addr);
+        }
+    }
+}
+
+static void sdp_write_header(char *buff, int size, struct sdp_session_level *s)
+{
+    av_strlcatf(buff, size, "v=%d\r\n"
+                            "o=- %d %d IN IPV4 %s\r\n"
+                            "t=%d %d\r\n"
+                            "s=%s\r\n"
+                            "a=tool:libavformat\r\n",
+                            s->sdp_version,
+                            s->id, s->version, s->src_addr,
+                            s->start_time, s->end_time,
+                            s->name[0] ? s->name : "No Name");
+    dest_write(buff, size, s->dst_addr, s->ttl);
+}
+
+static int get_address(char *dest_addr, int size, int *ttl, const char *url)
+{
+    int port;
+    const char *p;
+
+    url_split(NULL, 0, NULL, 0, dest_addr, size, &port, NULL, 0, url);
+
+    *ttl = 0;
+    p = strchr(url, '?');
+    if (p) {
+        char buff[64];
+        int is_multicast = find_info_tag(buff, sizeof(buff), "multicast", p);
+
+        if (is_multicast) {
+            if (find_info_tag(buff, sizeof(buff), "ttl", p)) {
+                *ttl = strtol(buff, NULL, 10);
+            } else {
+                *ttl = 5;
+            }
+        }
+    }
+
+    return port;
+}
+
+static void digit_to_char(char *dst, uint8_t src)
+{
+    if (src < 10) {
+        *dst = '0' + src;
+    } else {
+        *dst = 'A' + src - 10;
+    }
+}
+
+static char *data_to_hex(char *buff, const uint8_t *src, int s)
+{
+    int i;
+
+    for(i = 0; i < s; i++) {
+        digit_to_char(buff + 2 * i, src[i] >> 4);
+        digit_to_char(buff + 2 * i + 1, src[i] & 0xF);
+    }
+
+    return buff;
+}
+
+static char *sdp_media_attributes(char *buff, int size, AVCodecContext *c, int payload_type)
+{
+    char *config = NULL;
+
+    switch (c->codec_id) {
+        case CODEC_ID_MPEG4:
+            if (c->flags & CODEC_FLAG_GLOBAL_HEADER) {
+                if (c->extradata_size > MAX_EXTRADATA_SIZE) {
+                    av_log(NULL, AV_LOG_ERROR, "Too many extra data!\n");
+
+                    return NULL;
+                }
+                config = av_malloc(10 + c->extradata_size * 2);
+                if (config == NULL) {
+                    av_log(NULL, AV_LOG_ERROR, "Cannot allocate memory for the config info\n");
+                    return NULL;
+                }
+                memcpy(config, "; config=", 9);
+                data_to_hex(config + 9, c->extradata, c->extradata_size);
+                config[9 + c->extradata_size * 2] = 0;
+            }
+            av_strlcatf(buff, size, "a=rtpmap:%d MP4V-ES/90000\r\n"
+                                    "a=fmtp:%d profile-level-id=1%s\r\n",
+                                     payload_type,
+                                     payload_type, config ? config : "");
+            break;
+        default:
+            /* Nothing special to do, here... */
+            break;
+    }
+
+    av_free(config);
+
+    return buff;
+}
+
+static void sdp_write_media(char *buff, int size, AVCodecContext *c, const char *dest_addr, int port, int ttl)
+{
+    const char *type;
+    int payload_type;
+
+    payload_type = rtp_get_payload_type(c);
+    if (payload_type < 0) {
+        payload_type = 96;  /* FIXME: how to assign a private pt? rtp.c is broken too */
+    }
+
+    switch (c->codec_type) {
+        case CODEC_TYPE_VIDEO   : type = "video"      ; break;
+        case CODEC_TYPE_AUDIO   : type = "audio"      ; break;
+        case CODEC_TYPE_SUBTITLE: type = "text"       ; break;
+        default                 : type = "application"; break;
+    }
+
+    av_strlcatf(buff, size, "m=%s %d RTP/AVP %d\r\n", type, port, payload_type);
+    dest_write(buff, size, dest_addr, ttl);
+
+    sdp_media_attributes(buff, size, c, payload_type);
+}
+
+#define SDP_BUFFER_SIZE 2048
+char *avf_sdp_create(AVFormatContext *ac[], int n_files)
+{
+    char *buff;
+    struct sdp_session_level s;
+    int i, j, port, ttl;
+    char dst[32];
+
+    buff = av_mallocz(SDP_BUFFER_SIZE);
+    if (buff == NULL) {
+        return NULL;
+    }
+
+    memset(&s, 0, sizeof(struct sdp_session_level));
+    s.user = "-";
+    s.src_addr = "127.0.0.1";    /* FIXME: Properly set this */
+    s.name = ac[0]->title;
+
+    port = 0;
+    ttl = 0;
+    if (n_files == 1) {
+        port = get_address(dst, sizeof(dst), &ttl, ac[0]->filename);
+        if (port > 0) {
+            s.dst_addr = dst;
+            s.ttl = ttl;
+        }
+    }
+    sdp_write_header(buff, SDP_BUFFER_SIZE, &s);
+
+    dst[0] = 0;
+    for (i = 0; i < n_files; i++) {
+        if (n_files != 1) {
+            port = get_address(dst, sizeof(dst), &ttl, ac[i]->filename);
+        }
+        for (j = 0; j < ac[i]->nb_streams; j++) {
+            sdp_write_media(buff, SDP_BUFFER_SIZE,
+                                  ac[i]->streams[j]->codec, dst[0] ? dst : NULL,
+                                  (port > 0) ? port + j * 2 : 0, ttl);
+            if (port <= 0) {
+                av_strlcatf(buff, SDP_BUFFER_SIZE,
+                                   "a=control:streamid=%d\r\n", i + j);
+            }
+        }
+    }
+
+    return buff;
+}