add an RTP sender module

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@712 fefdeb5f-60dc-0310-8127-8f9354f1896f

src/modules/rtp/Makefile

@@ -0,0 +1,13 @@
+# This is a dirty trick just to ease compilation with emacs
+#
+# This file is not intended to be distributed or anything
+#
+# So: don't touch it, even better ignore it!
+
+all:
+	$(MAKE) -C ../..
+
+clean:
+	$(MAKE) -C ../.. clean
+
+.PHONY: all clean

src/modules/rtp/module-rtp-monitor.c

@@ -0,0 +1,340 @@
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <assert.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <polypcore/module.h>
+#include <polypcore/llist.h>
+#include <polypcore/source.h>
+#include <polypcore/source-output.h>
+#include <polypcore/memblockq.h>
+#include <polypcore/log.h>
+#include <polypcore/util.h>
+#include <polypcore/xmalloc.h>
+#include <polypcore/modargs.h>
+#include <polypcore/namereg.h>
+
+#include "module-rtp-monitor-symdef.h"
+
+#include "rtp.h"
+#include "sdp.h"
+#include "sap.h"
+
+PA_MODULE_AUTHOR("Lennart Poettering")
+PA_MODULE_DESCRIPTION("Read data from source and send it to the network via RTP")
+PA_MODULE_VERSION(PACKAGE_VERSION)
+PA_MODULE_USAGE(
+        "source=<name for the source> "
+        "format=<sample format> "
+        "channels=<number of channels> "
+        "rate=<sample rate> "
+        "destinaton=<destination IP address> "
+        "port=<port number> "
+        "mtu=<maximum transfer unit> "
+)
+
+#define DEFAULT_PORT 5666
+#define SAP_PORT 9875
+#define DEFAULT_DESTINATION "224.0.0.252"
+#define MEMBLOCKQ_MAXLENGTH (1024*170)
+#define DEFAULT_MTU 1024
+#define SAP_INTERVAL 5000000
+
+static const char* const valid_modargs[] = {
+    "source",
+    "format",
+    "channels",
+    "rate",
+    "destination",
+    "port",
+    NULL
+};
+
+struct userdata {
+    pa_module *module;
+    pa_core *core;
+
+    pa_source_output *source_output;
+    pa_memblockq *memblockq;
+
+    pa_rtp_context rtp_context;
+    pa_sap_context sap_context;
+    size_t mtu;
+
+    pa_time_event *sap_event;
+};
+
+static void source_output_push(pa_source_output *o, const pa_memchunk *chunk) {
+    struct userdata *u;
+    assert(o);
+    u = o->userdata;
+
+    if (pa_memblockq_push(u->memblockq, chunk) < 0) {
+        pa_log(__FILE__": Failed to push chunk into memblockq.");
+        return;
+    }
+    
+    pa_rtp_send(&u->rtp_context, u->mtu, u->memblockq);
+}
+
+static void source_output_kill(pa_source_output* o) {
+    struct userdata *u;
+    assert(o);
+    u = o->userdata;
+
+    pa_module_unload_request(u->module);
+
+    pa_source_output_disconnect(u->source_output);
+    pa_source_output_unref(u->source_output);
+    u->source_output = NULL;
+}
+
+static pa_usec_t source_output_get_latency (pa_source_output *o) {
+    struct userdata *u;
+    assert(o);
+    u = o->userdata;
+
+    return pa_bytes_to_usec(pa_memblockq_get_length(u->memblockq), &o->sample_spec);
+}
+
+static void sap_event(pa_mainloop_api *m, pa_time_event *t, const struct timeval *tv, void *userdata) {
+    struct userdata *u = userdata;
+    struct timeval next;
+    
+    assert(m);
+    assert(t);
+    assert(tv);
+    assert(u);
+
+    pa_sap_send(&u->sap_context, 0);
+
+    pa_log("SAP update");
+    pa_gettimeofday(&next);
+    pa_timeval_add(&next, SAP_INTERVAL);
+    m->time_restart(t, &next);
+}
+
+int pa__init(pa_core *c, pa_module*m) {
+    struct userdata *u;
+    pa_modargs *ma = NULL;
+    const char *dest;
+    uint32_t port = DEFAULT_PORT, mtu;
+    int af, fd = -1, sap_fd = -1;
+    pa_source *s;
+    pa_sample_spec ss;
+    pa_channel_map cm;
+    struct sockaddr_in sa4, sap_sa4;
+    struct sockaddr_in6 sa6, sap_sa6;
+    struct sockaddr_storage sa_dst;
+    pa_source_output *o = NULL;
+    uint8_t payload;
+    char *p;
+    int r;
+    socklen_t k;
+    struct timeval tv;
+    
+    assert(c);
+    assert(m);
+
+    if (!(ma = pa_modargs_new(m->argument, valid_modargs))) {
+        pa_log(__FILE__": failed to parse module arguments");
+        goto fail;
+    }
+
+    if (!(s = pa_namereg_get(m->core, pa_modargs_get_value(ma, "source", NULL), PA_NAMEREG_SOURCE, 1))) {
+        pa_log(__FILE__": source does not exist.");
+        goto fail;
+    }
+
+    ss = s->sample_spec;
+    pa_rtp_sample_spec_fixup(&ss);
+    cm = s->channel_map;
+    if (pa_modargs_get_sample_spec(ma, &ss) < 0) {
+        pa_log(__FILE__": failed to parse sample specification");
+        goto fail;
+    }
+
+    if (!pa_rtp_sample_spec_valid(&ss)) {
+        pa_log(__FILE__": specified sample type not compatible with RTP");
+        goto fail;
+    }
+
+    if (ss.channels != cm.channels)
+        pa_channel_map_init_auto(&cm, ss.channels);
+
+    payload = pa_rtp_payload_type(&ss);
+
+    mtu = (DEFAULT_MTU/pa_frame_size(&ss))*pa_frame_size(&ss);
+    
+    if (pa_modargs_get_value_u32(ma, "mtu", &mtu) < 0 || mtu < 1 || mtu % pa_frame_size(&ss) != 0) {
+        pa_log(__FILE__": invalid mtu.");
+        goto fail;
+    }
+    
+    if (pa_modargs_get_value_u32(ma, "port", &port) < 0 || port < 1 || port > 0xFFFF) {
+        pa_log(__FILE__": port= expects a numerical argument between 1 and 65535.");
+        goto fail;
+    }
+
+    if ((dest = pa_modargs_get_value(ma, "destination", DEFAULT_DESTINATION))) {
+        if (inet_pton(AF_INET6, dest, &sa6.sin6_addr) > 0) {
+            sa6.sin6_family = af = AF_INET6;
+            sa6.sin6_port = htons(port);
+            sap_sa6 = sa6;
+            sap_sa6.sin6_port = htons(SAP_PORT);
+        } else if (inet_pton(AF_INET, dest, &sa4.sin_addr) > 0) {
+            sa4.sin_family = af = AF_INET;
+            sa4.sin_port = htons(port);
+            sap_sa4 = sa4;
+            sap_sa4.sin_port = htons(SAP_PORT);
+        } else {
+            pa_log(__FILE__": invalid destination '%s'", dest);
+            goto fail;
+        }
+    }
+    
+    if ((fd = socket(af, SOCK_DGRAM, 0)) < 0) {
+        pa_log(__FILE__": socket() failed: %s", strerror(errno));
+        goto fail;
+    }
+
+    if (connect(fd, af == AF_INET ? (struct sockaddr*) &sa4 : (struct sockaddr*) &sa6, af == AF_INET ? sizeof(sa4) : sizeof(sa6)) < 0) {
+        pa_log(__FILE__": connect() failed: %s", strerror(errno));
+        goto fail;
+    }
+
+    if ((sap_fd = socket(af, SOCK_DGRAM, 0)) < 0) {
+        pa_log(__FILE__": socket() failed: %s", strerror(errno));
+        goto fail;
+    }
+
+    if (connect(sap_fd, af == AF_INET ? (struct sockaddr*) &sap_sa4 : (struct sockaddr*) &sap_sa6, af == AF_INET ? sizeof(sap_sa4) : sizeof(sap_sa6)) < 0) {
+        pa_log(__FILE__": connect() failed: %s", strerror(errno));
+        goto fail;
+    }
+
+    if (!(o = pa_source_output_new(s, __FILE__, "RTP Monitor Stream", &ss, &cm, PA_RESAMPLER_INVALID))) {
+        pa_log(__FILE__": failed to create source output.");
+        goto fail;
+    }
+
+    o->push = source_output_push;
+    o->kill = source_output_kill;
+    o->get_latency = source_output_get_latency;
+    o->owner = m;
+    
+    u = pa_xnew(struct userdata, 1);
+    m->userdata = u;
+    o->userdata = u;
+
+    u->module = m;
+    u->core = c;
+    u->source_output = o;
+    
+    u->memblockq = pa_memblockq_new(
+            0,
+            MEMBLOCKQ_MAXLENGTH,
+            MEMBLOCKQ_MAXLENGTH,
+            pa_frame_size(&ss),
+            1,
+            0,
+            NULL,
+            c->memblock_stat);
+
+    u->mtu = mtu;
+    
+    k = sizeof(sa_dst);
+    r = getsockname(fd, (struct sockaddr*) &sa_dst, &k);
+    assert(r >= 0);
+        
+    p = pa_sdp_build(af,
+                     af == AF_INET ? (void*) &((struct sockaddr_in*) &sa_dst)->sin_addr : (void*) &((struct sockaddr_in6*) &sa_dst)->sin6_addr,
+                     af == AF_INET ? (void*) &sa4.sin_addr : (void*) &sa6.sin6_addr,
+                     "Polypaudio RTP Stream", port, payload, &ss);
+    
+    pa_rtp_context_init_send(&u->rtp_context, fd, 0, payload);
+    pa_sap_context_init_send(&u->sap_context, sap_fd, p);
+
+    pa_log_info("RTP stream initialized with mtu %u on %s:%u, SSRC=0x%08x, payload=%u, initial sequence #%u", mtu, dest, port, u->rtp_context.ssrc, payload, u->rtp_context.sequence);
+    pa_log_info("SDP-Data:\n%s\nEOF", p);
+    
+    pa_sap_send(&u->sap_context, 0);
+
+    pa_gettimeofday(&tv);
+    pa_timeval_add(&tv, SAP_INTERVAL);
+    u->sap_event = c->mainloop->time_new(c->mainloop, &tv, sap_event, u);
+
+    pa_modargs_free(ma);
+
+    return 0;
+
+fail:
+    if (ma)
+        pa_modargs_free(ma);
+
+    if (fd >= 0)
+        close(fd);
+    
+    if (sap_fd >= 0)
+        close(sap_fd);
+
+    if (o) {
+        pa_source_output_disconnect(o);
+        pa_source_output_unref(o);
+    }
+        
+    return -1;
+}
+
+void pa__done(pa_core *c, pa_module*m) {
+    struct userdata *u;
+    assert(c);
+    assert(m);
+
+    if (!(u = m->userdata))
+        return;
+
+    c->mainloop->time_free(u->sap_event);
+    
+    if (u->source_output) {
+        pa_source_output_disconnect(u->source_output);
+        pa_source_output_unref(u->source_output);
+    }
+
+    pa_rtp_context_destroy(&u->rtp_context);
+
+    pa_sap_send(&u->sap_context, 1);
+    pa_sap_context_destroy(&u->sap_context);
+
+    pa_memblockq_free(u->memblockq);
+    
+    pa_xfree(u);
+}

src/modules/rtp/rtp.c

@@ -0,0 +1,193 @@
+/* $Id$ */
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <assert.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+
+#include <polypcore/log.h>
+
+#include "rtp.h"
+
+pa_rtp_context* pa_rtp_context_init_send(pa_rtp_context *c, int fd, uint32_t ssrc, uint8_t payload) {
+    assert(c);
+    assert(fd >= 0);
+
+    c->fd = fd;
+    c->sequence = (uint16_t) (rand()*rand());
+    c->timestamp = 0;
+    c->ssrc = ssrc ? ssrc : (uint32_t) (rand()*rand());
+    c->payload = payload & 127;
+
+    return c;
+}
+
+#define MAX_IOVECS 16
+
+int pa_rtp_send(pa_rtp_context *c, size_t size, pa_memblockq *q) {
+    struct iovec iov[MAX_IOVECS];
+    pa_memblock* mb[MAX_IOVECS];
+    int iov_idx = 1;
+    size_t n = 0, skip = 0;
+    
+    assert(c);
+    assert(size > 0);
+    assert(q);
+
+    if (pa_memblockq_get_length(q) < size)
+        return 0;
+    
+    for (;;) {
+        int r;
+        pa_memchunk chunk;
+
+        if ((r = pa_memblockq_peek(q, &chunk)) >= 0) {
+
+            size_t k = n + chunk.length > size ? size - n : chunk.length;
+
+            if (chunk.memblock) {
+                iov[iov_idx].iov_base = (uint8_t*) chunk.memblock->data + chunk.index;
+                iov[iov_idx].iov_len = k;
+                mb[iov_idx] = chunk.memblock;
+                iov_idx ++;
+
+                n += k;
+            }
+
+            skip += k;
+            pa_memblockq_drop(q, &chunk, k);
+        }
+
+        if (r < 0 || !chunk.memblock || n >= size || iov_idx >= MAX_IOVECS) {
+            uint32_t header[3];
+            struct msghdr m;
+            int k, i;
+
+            if (n > 0) {
+                header[0] = htonl(((uint32_t) 2 << 30) | ((uint32_t) c->payload << 16) | ((uint32_t) c->sequence));
+                header[1] = htonl(c->timestamp);
+                header[2] = htonl(c->ssrc);
+
+                iov[0].iov_base = header;
+                iov[0].iov_len = sizeof(header);
+                
+                m.msg_name = NULL;
+                m.msg_namelen = 0;
+                m.msg_iov = iov;
+                m.msg_iovlen = iov_idx;
+                m.msg_control = NULL;
+                m.msg_controllen = 0;
+                m.msg_flags = 0;
+                
+                k = sendmsg(c->fd, &m, MSG_DONTWAIT);
+
+                for (i = 1; i < iov_idx; i++)
+                    pa_memblock_unref(mb[i]);
+
+                c->sequence++;
+            } else
+                k = 0;
+
+            c->timestamp += skip;
+            
+            if (k < 0) {
+                if (errno != EAGAIN) /* If the queue is full, just ignore it */
+                    pa_log(__FILE__": sendmsg() failed: %s", strerror(errno));
+                return -1;
+            }
+            
+            if (r < 0 || pa_memblockq_get_length(q) < size)
+                break;
+
+            n = 0;
+            skip = 0;
+            iov_idx = 1;
+        }
+    }
+
+    return 0;
+}
+
+pa_rtp_context* pa_rtp_context_init_recv(pa_rtp_context *c, int fd) {
+    assert(c);
+
+    c->fd = fd;
+    return c;
+}
+
+int pa_rtp_recv(pa_rtp_context *c, pa_memchunk *chunk) {
+    assert(c);
+    assert(chunk);
+
+    return 0;
+}
+
+uint8_t pa_rtp_payload_type(const pa_sample_spec *ss) {
+    assert(ss);
+
+    if (ss->format == PA_SAMPLE_ULAW && ss->rate == 8000 && ss->channels == 1)
+        return 0;
+    if (ss->format == PA_SAMPLE_ALAW && ss->rate == 8000 && ss->channels == 1)
+        return 0;
+    if (ss->format == PA_SAMPLE_S16BE && ss->rate == 44100 && ss->channels == 2)
+        return 10;
+    if (ss->format == PA_SAMPLE_S16BE && ss->rate == 44100 && ss->channels == 1)
+        return 11;
+    
+    return 127;
+}
+
+pa_sample_spec *pa_rtp_sample_spec_fixup(pa_sample_spec * ss) {
+    assert(ss);
+
+    if (!pa_rtp_sample_spec_valid(ss))
+        ss->format = PA_SAMPLE_S16BE;
+
+    assert(pa_rtp_sample_spec_valid(ss));
+    return ss;
+}
+
+int pa_rtp_sample_spec_valid(const pa_sample_spec *ss) {
+    assert(ss);
+
+    if (!pa_sample_spec_valid(ss))
+        return 0;
+
+    return
+        ss->format == PA_SAMPLE_U8 ||
+        ss->format == PA_SAMPLE_ALAW ||
+        ss->format == PA_SAMPLE_ULAW ||
+        ss->format == PA_SAMPLE_S16BE;
+}
+
+void pa_rtp_context_destroy(pa_rtp_context *c) {
+    assert(c);
+
+    close(c->fd);
+}

src/modules/rtp/rtp.h

@@ -0,0 +1,51 @@
+#ifndef foortphfoo
+#define foortphfoo
+
+/* $Id$ */
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#include <inttypes.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <polypcore/memblockq.h>
+#include <polypcore/memchunk.h>
+
+typedef struct pa_rtp_context {
+    int fd;
+    uint16_t sequence;
+    uint32_t timestamp;
+    uint32_t ssrc;
+    uint8_t payload;
+} pa_rtp_context;
+
+pa_rtp_context* pa_rtp_context_init_send(pa_rtp_context *c, int fd, uint32_t ssrc, uint8_t payload);
+int pa_rtp_send(pa_rtp_context *c, size_t size, pa_memblockq *q);
+
+pa_rtp_context* pa_rtp_context_init_recv(pa_rtp_context *c, int fd);
+int pa_rtp_recv(pa_rtp_context *c, pa_memchunk *chunk);
+
+uint8_t pa_rtp_payload_type(const pa_sample_spec *ss);
+pa_sample_spec* pa_rtp_sample_spec_fixup(pa_sample_spec *ss);
+int pa_rtp_sample_spec_valid(const pa_sample_spec *ss);
+
+void pa_rtp_context_destroy(pa_rtp_context *c);
+
+#endif

src/modules/rtp/sap.c

@@ -0,0 +1,107 @@
+/* $Id$ */
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <assert.h>
+#include <time.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <polypcore/util.h>
+#include <polypcore/log.h>
+#include <polypcore/xmalloc.h>
+
+#include "sap.h"
+
+pa_sap_context* pa_sap_context_init_send(pa_sap_context *c, int fd, char *sdp_data) {
+    assert(c);
+    assert(fd >= 0);
+    assert(sdp_data);
+
+    c->fd = fd;
+    c->sdp_data = sdp_data;
+    c->msg_id_hash = (uint16_t) (rand()*rand());
+    
+    return c;    
+}
+
+void pa_sap_context_destroy(pa_sap_context *c) {
+    assert(c);
+
+    close(c->fd);
+    pa_xfree(c->sdp_data);
+}
+
+int pa_sap_send(pa_sap_context *c, int goodbye) {
+    uint32_t header;
+    const char mime[] = "application/sdp";
+    struct sockaddr_storage sa_buf;
+    struct sockaddr *sa = (struct sockaddr*) &sa_buf;
+    socklen_t salen = sizeof(sa_buf);
+    struct iovec iov[4];
+    struct msghdr m;
+    int k;
+
+    if (getsockname(c->fd, sa, &salen) < 0) {
+        pa_log("getsockname() failed: %s\n", strerror(errno));
+        return -1;
+    }
+
+    assert(sa->sa_family == AF_INET || sa->sa_family == AF_INET6);
+    
+    header = htonl(((uint32_t) 1 << 29) |
+                   (sa->sa_family == AF_INET6 ? (uint32_t) 1 << 28 : 0) |
+                   (goodbye ? (uint32_t) 1 << 26 : 0) |
+                   (c->msg_id_hash));
+
+    iov[0].iov_base = &header;
+    iov[0].iov_len = sizeof(header);
+
+    iov[1].iov_base = sa->sa_family == AF_INET ? (void*) &((struct sockaddr_in*) sa)->sin_addr : (void*) &((struct sockaddr_in6*) sa)->sin6_addr;
+    iov[1].iov_len = sa->sa_family == AF_INET ? 4 : 16;
+
+    iov[2].iov_base = (char*) mime;
+    iov[2].iov_len = sizeof(mime);
+
+    iov[3].iov_base = c->sdp_data;
+    iov[3].iov_len = strlen(c->sdp_data);
+                   
+    m.msg_name = NULL;
+    m.msg_namelen = 0;
+    m.msg_iov = iov;
+    m.msg_iovlen = 4;
+    m.msg_control = NULL;
+    m.msg_controllen = 0;
+    m.msg_flags = 0;
+    
+    if ((k = sendmsg(c->fd, &m, MSG_DONTWAIT)) < 0)
+        pa_log("sendmsg() failed: %s\n", strerror(errno));
+
+    return k;
+}

src/modules/rtp/sap.h

@@ -0,0 +1,43 @@
+#ifndef foosaphfoo
+#define foosaphfoo
+
+/* $Id$ */
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#include <inttypes.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <polypcore/memblockq.h>
+#include <polypcore/memchunk.h>
+
+typedef struct pa_sap_context {
+    int fd;
+    char *sdp_data;
+
+    uint16_t msg_id_hash;
+} pa_sap_context;
+
+pa_sap_context* pa_sap_context_init_send(pa_sap_context *c, int fd, char *sdp_data);
+void pa_sap_context_destroy(pa_sap_context *c);
+
+int pa_sap_send(pa_sap_context *c, int goodbye);
+
+#endif

src/modules/rtp/sdp.c

@@ -0,0 +1,87 @@
+/* $Id$ */
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <assert.h>
+#include <time.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+#include <polypcore/util.h>
+
+#include "sdp.h"
+
+static const char* map_format(pa_sample_format_t f) {
+    switch (f) {
+        case PA_SAMPLE_S16BE: return "L16";
+        case PA_SAMPLE_U8: return "L8";
+        case PA_SAMPLE_ALAW: return "PCMA";
+        case PA_SAMPLE_ULAW: return "PCMU";
+        default:
+            return NULL;
+    }
+}
+
+char *pa_sdp_build(int af, const void *src, const void *dst, const char *name, uint16_t port, uint8_t payload, const pa_sample_spec *ss) {
+    uint32_t ntp;
+    char buf_src[64], buf_dst[64];
+    const char *u, *f, *a;
+
+    assert(src);
+    assert(dst);
+    assert(af == AF_INET || af == AF_INET6);
+
+    f = map_format(ss->format);
+    assert(f);
+    
+    if (!(u = getenv("USER")))
+        if (!(u = getenv("USERNAME")))
+            u = "-";
+    
+    ntp = time(NULL) + 2208988800;
+
+    a = inet_ntop(af, src, buf_src, sizeof(buf_src));
+    assert(a);
+    a = inet_ntop(af, dst, buf_dst, sizeof(buf_dst));
+    assert(a);
+    
+    return pa_sprintf_malloc(
+            "v=0\n"
+            "o=%s %lu 0 IN %s %s\n"
+            "s=%s\n"
+            "c=IN %s %s\n"
+            "t=%lu 0\n"
+            "a=recvonly\n"
+            "m=audio %u RTP/AVP %i\n"
+            "a=rtpmap:%i %s/%u/%u\n"
+            "a=type:broadcast\n",
+            u, (unsigned long) ntp, af == AF_INET ? "IP4" : "IP6", buf_src,
+            name,
+            af == AF_INET ? "IP4" : "IP6", buf_dst,
+            (unsigned long) ntp,
+            port, payload,
+            payload, f, ss->rate, ss->channels);
+}

src/modules/rtp/sdp.h

@@ -0,0 +1,33 @@
+#ifndef foosdphfoo
+#define foosdphfoo
+
+/* $Id$ */
+
+/***
+  This file is part of polypaudio.
+ 
+  polypaudio 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 of the License,
+  or (at your option) any later version.
+ 
+  polypaudio 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
+  General Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public License
+  along with polypaudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#include <inttypes.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <polyp/sample.h>
+
+char *pa_sdp_build(int af, const void *src, const void *dst, const char *name, uint16_t port, uint8_t payload, const pa_sample_spec *ss);
+
+#endif