Add WebRTC support using libdatachannel

The WebRTC is exposed via `/video.html` endpoint
and enabled by default as long as h264 stream
is available.

.gitignore

@@ -1,7 +1,8 @@
 tmp/
 *.o
 *.d
-html/*.c
+*.html.c
+*.js.c
 /camera-streamer
 /test_*
 .vscode/settings.json

.gitmodules

@@ -0,0 +1,4 @@
+[submodule "third_party/libdatachannel"]
+	path = third_party/libdatachannel
+	url = https://github.com/paullouisageneau/libdatachannel.git
+	ignore = dirty

.vscode/c_cpp_properties.json

@@ -4,6 +4,8 @@
             "name": "Linux",
             "includePath": [
                 "${workspaceFolder}/**",
+                "${workspaceFolder}/third_party/libdatachannel/include",
+                "${workspaceFolder}/third_party/libdatachannel/deps/json/include",
                 "/usr/include/libcamera",
                 "/usr/include/liveMedia",
                 "/usr/include/groupsock",
@@ -13,7 +15,8 @@
             "defines": [
                 "USE_LIBCAMERA=1",
                 "USE_FFMPEG=1",
-                "USE_RTSP=1"
+                "USE_RTSP=1",
+                "USE_LIBDATACHANNEL=1"
             ],
             "compilerPath": "/usr/bin/gcc",
             "cStandard": "gnu17",

Dockerfile

@@ -24,5 +24,5 @@ ADD / /src
 WORKDIR /src
 RUN git clean -ffdx
 RUN git submodule update --init --recursive --recommend-shallow
-RUN git submodule foreach git clean -ffdx
+RUN git submodule foreach --recursive git clean -ffdx
 RUN make -j$(nproc)

Makefile

@@ -10,9 +10,12 @@ ifneq (x,x$(shell which ccache))
 CCACHE ?= ccache
 endif
 
+LIBDATACHANNEL_PATH ?= third_party/libdatachannel
+
 USE_FFMPEG ?= $(shell pkg-config libavutil libavformat libavcodec && echo 1)
 USE_LIBCAMERA ?= $(shell pkg-config libcamera && echo 1)
 USE_RTSP ?= $(shell pkg-config live555 && echo 1)
+USE_LIBDATACHANNEL ?= $(shell [ -e $(LIBDATACHANNEL_PATH)/CMakeLists.txt ] && echo 1)
 
 ifeq (1,$(DEBUG))
 CFLAGS += -g
@@ -33,6 +36,19 @@ CFLAGS += -DUSE_RTSP $(shell pkg-config --cflags live555)
 LDLIBS += $(shell pkg-config --libs live555)
 endif
 
+ifeq (1,$(USE_LIBDATACHANNEL))
+CFLAGS += -DUSE_LIBDATACHANNEL
+CFLAGS += -I$(LIBDATACHANNEL_PATH)/include
+CFLAGS += -I$(LIBDATACHANNEL_PATH)/deps/json/include
+LDLIBS += -L$(LIBDATACHANNEL_PATH)/build -ldatachannel-static
+LDLIBS += -L$(LIBDATACHANNEL_PATH)/build/deps/usrsctp/usrsctplib -lusrsctp
+LDLIBS += -L$(LIBDATACHANNEL_PATH)/build/deps/libsrtp -lsrtp2
+LDLIBS += -L$(LIBDATACHANNEL_PATH)/build/deps/libjuice -ljuice-static
+LDLIBS += -lcrypto -lssl
+
+camera-streamer: $(LIBDATACHANNEL_PATH)/build/libdatachannel-static.a
+endif
+
 HTML_SRC = $(addsuffix .c,$(HTML))
 OBJS = $(patsubst %.cc,%.o,$(patsubst %.c,%.o,$(SRC) $(HTML_SRC)))
 
@@ -40,7 +56,7 @@ OBJS = $(patsubst %.cc,%.o,$(patsubst %.c,%.o,$(SRC) $(HTML_SRC)))
 
 all: $(TARGET)
 
-%: cmd/% $(OBJS)
+%: cmd/% $(filter-out third_party/%, $(OBJS))
 	$(CCACHE) $(CXX) $(CFLAGS) -o $@ $(filter-out cmd/%, $^) $(filter $</%, $^) $(LDLIBS)
 
 install: $(TARGET)
@@ -64,3 +80,7 @@ headers:
 html/%.c: html/%
 	xxd -i $< > $@.tmp
 	mv $@.tmp $@
+
+$(LIBDATACHANNEL_PATH)/build/libdatachannel-static.a: $(LIBDATACHANNEL_PATH)
+	[ -e $</build/Makefile ] || cmake -S $< -B $</build
+	$(MAKE) -C $</build datachannel-static

README.md

@@ -43,7 +43,10 @@ reboot
 ## Compile
 
 ```bash
-apt-get -y install libavformat-dev libavutil-dev libavcodec-dev libcamera-dev liblivemedia-dev v4l-utils pkg-config xxd build-essential
+git clone https://github.com/ayufan-research/camera-streamer.git --recursive
+apt-get -y install libavformat-dev libavutil-dev libavcodec-dev libcamera-dev liblivemedia-dev v4l-utils pkg-config xxd build-essential cmake libssl-dev
+
+cd camera-streamer/
 make
 sudo make install
 ```
@@ -263,6 +266,14 @@ device/buffer_lock.c: http_jpeg: Captured buffer JPEG:capture:mplane:buf1 (refs=
 device/buffer_lock.c: http_jpeg: Captured buffer JPEG:capture:mplane:buf2 (refs=2), frame=159/0, processing_ms=18.5, frame_ms=8.3
 ```
 
+## WebRTC support
+
+The WebRTC is accessible via `http://<ip>:8080/video` by default and is available when there's H264 output generated.
+
+WebRTC support is implemented using awesome [libdatachannel](https://github.com/paullouisageneau/libdatachannel/) library.
+
+The support will be compiled by default when doing `make`.
+
 ## License
 
 GNU General Public License v3.0

cmd/camera-streamer/http.c

@@ -2,6 +2,7 @@
 #include "util/opts/opts.h"
 #include "util/opts/log.h"
 #include "util/opts/fourcc.h"
+#include "output/webrtc/webrtc.h"
 #include "device/camera/camera.h"
 #include "output/output.h"
 #include "output/rtsp/rtsp.h"
@@ -10,8 +11,6 @@ extern unsigned char html_index_html[];
 extern unsigned int html_index_html_len;
 extern unsigned char html_video_html[];
 extern unsigned int html_video_html_len;
-extern unsigned char html_jmuxer_min_js[];
-extern unsigned int html_jmuxer_min_js_len;
 extern camera_t *camera;
 
 void *camera_http_set_option(http_worker_t *worker, FILE *stream, const char *key, const char *value, void *headersp)
@@ -81,8 +80,8 @@ http_method_t http_methods[] = {
   { "GET /video.h264?", http_h264_video },
   { "GET /video.mkv?", http_mkv_video },
   { "GET /video.mp4?", http_mp4_video },
+  { "POST /video?", http_webrtc_offer },
   { "GET /option?", camera_http_option },
-  { "GET /jmuxer.min.js?", http_content, "text/javascript", html_jmuxer_min_js, 0, &html_jmuxer_min_js_len },
   { "GET /?", http_content, "text/html", html_index_html, 0, &html_index_html_len },
   { }
 };

cmd/camera-streamer/main.c

@@ -1,9 +1,9 @@
 #include "util/http/http.h"
 #include "util/opts/opts.h"
 #include "util/opts/log.h"
-#include "util/opts/fourcc.h"
 #include "device/camera/camera.h"
 #include "output/rtsp/rtsp.h"
+#include "output/webrtc/webrtc.h"
 
 #include <signal.h>
 #include <unistd.h>
@@ -46,6 +46,8 @@ int main(int argc, char *argv[])
     goto error;
   }
 
+  webrtc_server();
+
   while (true) {
     camera = camera_open(&camera_options);
     if (camera) {

html/index.html

@@ -40,7 +40,7 @@
 		<br>
 		<li>
 			<a href="video"><b>/video</b></a><br>
-			Get a live video (H264) stream.<br>
+			Get a live WebRTC (H264) stream.<br>
 			<br>
 			<ul>
 				<li><a href="video.mp4"><b>/video.mp4</b></a><br> get a live video stream in MP4 format (if FFMPEG enabled).</li>

html/video.html

@@ -1,26 +1,25 @@
 <!doctype html>
-
 <html lang="en">
 <head>
-<meta charset="utf-8">
-<title></title>
-<link rel="icon" href="data:;base64,iVBORw0KGgo=">
-<style>
-body {
+  <meta charset="utf-8">
+  <title></title>
+  <link rel="icon" href="data:;base64,iVBORw0KGgo=">
+  <style>
+    body {
       margin:0;
       padding:0;
       background-color:#303030;
-}
+    }
 
-#streamStage {
+    #streamStage {
       position:fixed;
       top:0;
       left:0;
       width:100%;
       height:100%;
-}
+    }
 
-#streamStage:before {
+    #streamStage:before {
       content: '';
       box-sizing: border-box;
       position: absolute;
@@ -30,53 +29,113 @@ body {
       height: 2rem;
       margin-top: -1rem;
       margin-left: -1rem;
-}
+    }
 
-#stream {
+    #stream {
       max-height: 100%;
       max-width: 100%;
       margin: auto;
       position: absolute;
       top: 0; left: 0; bottom: 0; right: 0;
-}
-</style>
-<script src="/jmuxer.min.js"></script>
+    }
+  </style>
 </head>
 <body>
   <div id="streamtage">
     <video controls autoplay muted id="stream"></video>
   </div>
-<body>
+
+  <script>
+    function startWebRTC() {
+        var config = {
+            sdpSemantics: 'unified-plan'
+        };
+
+        if (!document.getElementById('use-stun') || document.getElementById('use-stun').checked) {
+          config.iceServers = [{urls: ['stun:stun.l.google.com:19302']}];
+        }
+
+        pc = new RTCPeerConnection(config);
+        pc.addTransceiver('video', {direction: 'recvonly'});
+        //pc.addTransceiver('audio', {direction: 'recvonly'});
+        pc.addEventListener('track', function(evt) {
+          console.log("track event " + evt.track.kind);
+            if (evt.track.kind == 'video') {
+                if (document.getElementById('stream'))
+                  document.getElementById('stream').srcObject = evt.streams[0];
+            } else {
+                if (document.getElementById('audio'))
+                  document.getElementById('audio').srcObject = evt.streams[0];
+            }
+        });
+
+        const urlSearchParams = new URLSearchParams(window.location.search);
+        const params = Object.fromEntries(urlSearchParams.entries());
+
+        fetch('/video', {
+          body: JSON.stringify({
+              type: 'request',
+              res: params.res
+          }),
+          headers: {
+              'Content-Type': 'application/json'
+          },
+          method: 'POST'
+        }).then(function(response) {
+          return response.json();
+        }).then(function(answer) {
+          pc.remote_pc_id = answer.id;
+          return pc.setRemoteDescription(answer);
+        }).then(function() {
+          return pc.createAnswer();
+        }).then(function(answer) {
+          return pc.setLocalDescription(answer);
+        }).then(function() {
+            // wait for ICE gathering to complete
+            return new Promise(function(resolve) {
+                if (pc.iceGatheringState === 'complete') {
+                    resolve();
+                } else {
+                    function checkState() {
+                        if (pc.iceGatheringState === 'complete') {
+                            pc.removeEventListener('icegatheringstatechange', checkState);
+                            resolve();
+                        }
+                    }
+                    pc.addEventListener('icegatheringstatechange', checkState);
+                }
+            });
+        }).then(function(answer) {
+          var offer = pc.localDescription;
+
+          return fetch('/video', {
+            body: JSON.stringify({
+                type: offer.type,
+                id: pc.remote_pc_id,
+                sdp: offer.sdp,
+            }),
+            headers: {
+                'Content-Type': 'application/json'
+            },
+            method: 'POST'
+          })
+        }).then(function(response) {
+            return response.json();
+        }).catch(function(e) {
+            alert(e);
+        });
+    }
+
+    function stopWebRTC() {
+        setTimeout(function() {
+            pc.close();
+        }, 500);
+      }
+  </script>
+
   <script>
     window.onload = function() {
-		var jmuxer = new JMuxer({
-			node: 'stream',
-			mode: 'video',
-			flushingTime: 0,
-			fps: 30,
-			debug: false
-		 });
-
-    fetch('/video.h264' + window.location.search).then(function(response) {
-      console.log(response);
-
-      const reader = response.body.getReader();
-
-      function go() {
-        reader.read().then(function(result) {
-          if (!result.done) {
-            if (!document.hidden){
-              jmuxer.feed({
-                video: new Uint8Array(result.value)
-              });
-            }
-            go ();
-          }
-        })
-      }
-
-      go ();
-    })
+      startWebRTC();
     }
   </script>
 </body>

output/http_h264.c

@@ -35,11 +35,17 @@ bool h264_is_key_frame(buffer_t *buf)
 {
   unsigned char *data = buf->start;
 
+  static const int N = 8;
+  char buffer [3*N+1];
+  buffer[sizeof(buffer)-1] = 0;
+  for(int j = 0; j < N; j++)
+    sprintf(&buffer[sizeof(buffer)/N*j], "%02X ", data[j]);
+
   if (buf->flags.is_keyframe) {
-    LOG_DEBUG(buf, "Got key frame (from V4L2)!");
+    LOG_DEBUG(buf, "Got key frame (from V4L2)!: %s", buffer);
     return true;
   } else if (buf->used >= 5 && (data[4] & 0x1F) == 0x07) {
-    LOG_DEBUG(buf, "Got key frame (from buffer)!");
+    LOG_DEBUG(buf, "Got key frame (from buffer)!: %s", buffer);
     return true;
   }
 

output/webrtc/webrtc.cc

@@ -0,0 +1,426 @@
+extern "C" {
+#include "webrtc.h"
+#include "device/buffer.h"
+#include "device/buffer_list.h"
+#include "device/buffer_lock.h"
+#include "device/device.h"
+#include "output/output.h"
+};
+
+#ifdef USE_LIBDATACHANNEL
+
+#include <string>
+#include <memory>
+#include <optional>
+#include <condition_variable>
+#include <atomic>
+#include <chrono>
+#include <set>
+#include <nlohmann/json.hpp>
+#include <rtc/peerconnection.hpp>
+#include <rtc/rtcpsrreporter.hpp>
+#include <rtc/h264rtppacketizer.hpp>
+#include <rtc/h264packetizationhandler.hpp>
+#include <rtc/rtcpnackresponder.hpp>
+
+using namespace std::chrono_literals;
+
+class Client;
+
+static std::set<std::shared_ptr<Client> > webrtc_clients;
+static std::mutex webrtc_clients_lock;
+static const auto webrtc_client_lock_timeout = 3 * 1000ms;
+static const auto webrtc_client_max_json_body = 10 * 1024;
+static const auto webrtc_client_video_payload_type = 102; // H264
+static const rtc::Configuration webrtc_configuration = {
+  .iceServers = { rtc::IceServer("stun:stun.l.google.com:19302") },
+  .disableAutoNegotiation = true  
+};
+
+struct ClientTrackData
+{
+  std::shared_ptr<rtc::Track> track;
+	std::shared_ptr<rtc::RtcpSrReporter> sender;
+
+  void startStreaming()
+  {
+    double currentTime_s = get_monotonic_time_us(NULL, NULL)/(1000.0*1000.0);
+    sender->rtpConfig->setStartTime(currentTime_s, rtc::RtpPacketizationConfig::EpochStart::T1970);
+    sender->startRecording();
+  }
+
+  void sendTime()
+  {
+    double currentTime_s = get_monotonic_time_us(NULL, NULL)/(1000.0*1000.0);
+
+    auto rtpConfig = sender->rtpConfig;
+    uint32_t elapsedTimestamp = rtpConfig->secondsToTimestamp(currentTime_s);
+
+    sender->rtpConfig->timestamp = sender->rtpConfig->startTimestamp + elapsedTimestamp;
+    auto reportElapsedTimestamp = sender->rtpConfig->timestamp - sender->previousReportedTimestamp;
+    if (sender->rtpConfig->timestampToSeconds(reportElapsedTimestamp) > 1) {
+      sender->setNeedsToReport();
+    }
+  }
+
+  bool wantsFrame() const
+  {
+    if (!track)
+      return false;
+
+    return track->isOpen();
+  }
+};
+
+class Client
+{
+public:
+  Client(std::shared_ptr<rtc::PeerConnection> pc_)
+    : pc(pc_), use_low_res(false)
+  {
+    id.resize(20);
+    for (auto & c : id) {
+      c = 'a' + (rand() % 26);
+    }
+    id = "rtc-" + id;
+    name = strdup(id.c_str());
+  }
+
+  ~Client()
+  {
+    free(name);
+  }
+
+  bool wantsFrame() const
+  {
+    if (!pc || !video)
+      return false;
+    if (pc->state() != rtc::PeerConnection::State::Connected)
+      return false;
+    return video->wantsFrame();
+  }
+
+  void pushFrame(buffer_t *buf, bool low_res)
+  {
+    auto self = this;
+
+    if (!video || !video->track) {
+      return;
+    }
+
+    if (use_low_res != low_res) {
+      return;
+    }
+
+    if (!had_key_frame) {
+      if (!h264_is_key_frame(buf)) {
+        device_video_force_key(buf->buf_list->dev);
+        LOG_VERBOSE(self, "Skipping as key frame was not yet sent.");
+        return;
+      }
+      had_key_frame = true;
+    }
+
+    rtc::binary data((std::byte*)buf->start, (std::byte*)buf->start + buf->used);
+    video->sendTime();
+    video->track->send(data);
+  }
+
+public:
+  char *name;
+  std::string id;
+  std::shared_ptr<rtc::PeerConnection> pc;
+  std::shared_ptr<ClientTrackData> video;
+  std::mutex lock;
+  std::condition_variable wait_for_complete;
+  bool had_key_frame;
+  bool use_low_res;
+};
+
+std::shared_ptr<Client> findClient(std::string id)
+{
+  std::unique_lock lk(webrtc_clients_lock);
+  for (auto client : webrtc_clients) {
+    if (client && client->id == id) {
+      return client;
+    }
+  }
+
+  return std::shared_ptr<Client>();
+}
+
+void removeClient(const std::shared_ptr<Client> &client, const char *reason)
+{
+  std::unique_lock lk(webrtc_clients_lock);
+  webrtc_clients.erase(client);
+  LOG_INFO(client.get(), "Client removed: %s.", reason);
+}
+
+std::shared_ptr<ClientTrackData> addVideo(const std::shared_ptr<rtc::PeerConnection> pc, const uint8_t payloadType, const uint32_t ssrc, const std::string cname, const std::string msid)
+{
+  auto video = rtc::Description::Video(cname, rtc::Description::Direction::SendOnly);
+  video.addH264Codec(payloadType);
+  video.setBitrate(1000);
+  video.addSSRC(ssrc, cname, msid, cname);
+  auto track = pc->addTrack(video);
+  auto rtpConfig = std::make_shared<rtc::RtpPacketizationConfig>(ssrc, cname, payloadType, rtc::H264RtpPacketizer::defaultClockRate);
+  auto packetizer = std::make_shared<rtc::H264RtpPacketizer>(rtc::H264RtpPacketizer::Separator::LongStartSequence, rtpConfig);
+  auto h264Handler = std::make_shared<rtc::H264PacketizationHandler>(packetizer);
+  auto srReporter = std::make_shared<rtc::RtcpSrReporter>(rtpConfig);
+  h264Handler->addToChain(srReporter);
+  auto nackResponder = std::make_shared<rtc::RtcpNackResponder>();
+  h264Handler->addToChain(nackResponder);
+  track->setMediaHandler(h264Handler);
+  return std::shared_ptr<ClientTrackData>(new ClientTrackData{track, srReporter});
+}
+
+std::shared_ptr<Client> createPeerConnection(const rtc::Configuration &config)
+{
+  auto pc = std::make_shared<rtc::PeerConnection>(config);
+  auto client = std::make_shared<Client>(pc);
+  auto wclient = std::weak_ptr(client);
+
+  pc->onTrack([wclient](std::shared_ptr<rtc::Track> track) {
+    if(auto client = wclient.lock()) {
+      LOG_DEBUG(client.get(), "onTrack: %s", track->mid().c_str());
+    }
+  });
+
+  pc->onLocalDescription([wclient](rtc::Description description) {
+    if(auto client = wclient.lock()) {
+      LOG_DEBUG(client.get(), "onLocalDescription: %s", description.typeString().c_str());
+    }
+  });
+
+  pc->onSignalingStateChange([wclient](rtc::PeerConnection::SignalingState state) {
+    if(auto client = wclient.lock()) {
+      LOG_DEBUG(client.get(), "onSignalingStateChange: %d", (int)state);
+    }
+  });
+
+  pc->onStateChange([wclient](rtc::PeerConnection::State state) {
+    if(auto client = wclient.lock()) {
+      LOG_DEBUG(client.get(), "onStateChange: %d", (int)state);
+
+      if (state == rtc::PeerConnection::State::Disconnected ||
+        state == rtc::PeerConnection::State::Failed ||
+        state == rtc::PeerConnection::State::Closed)
+      {
+        removeClient(client, "stream closed");
+      }
+    }
+  });
+
+  pc->onGatheringStateChange([wclient](rtc::PeerConnection::GatheringState state) {
+    if(auto client = wclient.lock()) {
+      LOG_DEBUG(client.get(), "onGatheringStateChange: %d", (int)state);
+
+      if (state == rtc::PeerConnection::GatheringState::Complete) {
+        client->wait_for_complete.notify_all();
+      }
+    }
+  });
+
+  std::unique_lock lk(webrtc_clients_lock);
+  webrtc_clients.insert(client);
+  return client;
+}
+
+static bool webrtc_h264_needs_buffer(buffer_lock_t *buf_lock)
+{
+  std::unique_lock lk(webrtc_clients_lock);
+  for (auto client : webrtc_clients) {
+    if (client->wantsFrame())
+      return true;
+  }
+
+  return false;
+}
+
+static void webrtc_h264_capture(buffer_lock_t *buf_lock, buffer_t *buf)
+{
+  std::unique_lock lk(webrtc_clients_lock);
+  for (auto client : webrtc_clients) {
+    if (client->wantsFrame()) {
+      client->pushFrame(buf, false);
+
+      if (!http_h264_lowres.buf_list) {
+        client->pushFrame(buf, true);
+      }
+    }
+  }
+}
+
+static void webrtc_h264_low_res_capture(buffer_lock_t *buf_lock, buffer_t *buf)
+{
+  std::unique_lock lk(webrtc_clients_lock);
+  for (auto client : webrtc_clients) {
+    if (client->wantsFrame()) {
+      client->pushFrame(buf, true);
+    }
+  }
+}
+
+static void http_webrtc_request(http_worker_t *worker, FILE *stream, const nlohmann::json &message)
+{
+  auto client = createPeerConnection(webrtc_configuration);
+  LOG_INFO(client.get(), "Stream requested.");
+
+  client->video = addVideo(client->pc, webrtc_client_video_payload_type, rand(), "video", "");
+  if (message.contains("res")) {
+    client->use_low_res = (message["res"] == "low");
+  }
+
+  try {
+    {
+      std::unique_lock lock(client->lock);
+      client->pc->setLocalDescription();
+      client->wait_for_complete.wait_for(lock, webrtc_client_lock_timeout);
+    }
+
+    if (client->pc->gatheringState() == rtc::PeerConnection::GatheringState::Complete) {
+      auto description = client->pc->localDescription();
+      nlohmann::json message;
+      message["id"] = client->id;
+      message["type"] = description->typeString();
+      message["sdp"] = std::string(description.value());
+      http_write_response(stream, "200 OK", "application/json", message.dump().c_str(), 0);
+      LOG_VERBOSE(client.get(), "Local SDP Offer: %s", std::string(message["sdp"]).c_str());
+    } else {
+      http_500(stream, "Not complete");
+    }
+  } catch(const std::exception &e) {
+    http_500(stream, e.what());
+    removeClient(client, e.what());
+  }
+}
+
+static void http_webrtc_answer(http_worker_t *worker, FILE *stream, const nlohmann::json &message)
+{
+  if (!message.contains("id") || !message.contains("sdp")) {
+    http_400(stream, "no sdp or id");
+    return;
+  }
+
+  if (auto client = findClient(message["id"])) {
+    LOG_INFO(client.get(), "Answer received.");
+    LOG_VERBOSE(client.get(), "Remote SDP Answer: %s", std::string(message["sdp"]).c_str());
+
+    try {
+      auto answer = rtc::Description(std::string(message["sdp"]), std::string(message["type"]));
+      client->pc->setRemoteDescription(answer);
+      client->video->startStreaming();
+      http_write_response(stream, "200 OK", "application/json", "{}", 0);
+    } catch(const std::exception &e) {
+      http_500(stream, e.what());
+      removeClient(client, e.what());
+    }
+  } else {
+    http_404(stream, "No client found");
+  }
+}
+
+static void http_webrtc_offer(http_worker_t *worker, FILE *stream, const nlohmann::json &message)
+{
+  if (!message.contains("sdp")) {
+    http_400(stream, "no sdp");
+    return;
+  }
+
+  auto offer = rtc::Description(std::string(message["sdp"]), std::string(message["type"]));
+  auto client = createPeerConnection(webrtc_configuration);
+
+  LOG_INFO(client.get(), "Offer received.");
+  LOG_VERBOSE(client.get(), "Remote SDP Offer: %s", std::string(message["sdp"]).c_str());
+
+  try {
+    client->video = addVideo(client->pc, webrtc_client_video_payload_type, rand(), "video", "");
+    client->video->startStreaming();
+
+    {
+      std::unique_lock lock(client->lock);
+      client->pc->setRemoteDescription(offer);
+      client->pc->setLocalDescription();
+      client->wait_for_complete.wait_for(lock, webrtc_client_lock_timeout);
+    }
+
+    if (client->pc->gatheringState() == rtc::PeerConnection::GatheringState::Complete) {
+      auto description = client->pc->localDescription();
+      nlohmann::json message;
+      message["type"] = description->typeString();
+      message["sdp"] = std::string(description.value());
+      http_write_response(stream, "200 OK", "application/json", message.dump().c_str(), 0);
+
+      LOG_VERBOSE(client.get(), "Local SDP Answer: %s", std::string(message["sdp"]).c_str());
+    } else {
+      http_500(stream, "Not complete");
+    }
+  } catch(const std::exception &e) {
+    http_500(stream, e.what());
+    removeClient(client, e.what());
+  }
+}
+
+nlohmann::json http_parse_json_body(http_worker_t *worker, FILE *stream)
+{
+  std::string text;
+
+  size_t i = 0;
+  size_t n = (size_t)worker->content_length;
+  if (n < 0 || n > webrtc_client_max_json_body)
+    n = webrtc_client_max_json_body;
+
+  text.resize(n);
+
+  while (i < n && !feof(stream)) {
+    i += fread(&text[i], 1, n-i, stream);
+  }
+  text.resize(i);
+
+  return nlohmann::json::parse(text);
+}
+
+extern "C" void http_webrtc_offer(http_worker_t *worker, FILE *stream)
+{
+  auto message = http_parse_json_body(worker, stream);
+
+  if (!message.contains("type")) {
+    http_400(stream, "missing 'type'");
+    return;
+  }
+
+  std::string type = message["type"];
+
+  LOG_DEBUG(worker, "Recevied: '%s'", type.c_str());
+
+  if (type == "request") {
+    http_webrtc_request(worker, stream, message);
+  } else if (type == "answer") {
+    http_webrtc_answer(worker, stream, message);
+  } else if (type == "offer") {
+    http_webrtc_offer(worker, stream, message);
+  } else {
+    http_400(stream, (std::string("Not expected: " + type)).c_str());
+  }
+}
+
+extern "C" void webrtc_server()
+{
+  buffer_lock_register_check_streaming(&http_h264, webrtc_h264_needs_buffer);
+  buffer_lock_register_notify_buffer(&http_h264, webrtc_h264_capture);
+  buffer_lock_register_check_streaming(&http_h264_lowres, webrtc_h264_needs_buffer);
+  buffer_lock_register_notify_buffer(&http_h264_lowres, webrtc_h264_low_res_capture);
+}
+
+#else // USE_LIBDATACHANNEL
+
+extern "C" void http_webrtc_offer(http_worker_t *worker, FILE *stream)
+{
+  http_404(stream, NULL);
+}
+
+extern "C" void webrtc_server()
+{
+}
+
+#endif // USE_LIBDATACHANNEL

output/webrtc/webrtc.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "util/http/http.h"
+#include "util/opts/log.h"
+#include "util/opts/fourcc.h"
+#include "util/opts/control.h"
+#include "device/buffer.h"
+
+// WebRTC
+void http_webrtc_offer(http_worker_t *worker, FILE *stream);
+void webrtc_server();

third_party/libdatachannel

@@ -0,0 +1 @@
+Subproject commit 04cf4738961f55ba3f0aa39b4a61342f66bb3781

util/http/http.c

@@ -14,6 +14,9 @@
 #include "http.h"
 #include "util/opts/log.h"
 
+#define HEADER_RANGE "Range:"
+#define HEADER_CONTENT_LENGTH "Content-Length:"
+
 static int http_listen(int port, int maxcons)
 {
   struct sockaddr_in server = {0};
@@ -92,6 +95,7 @@ static void http_process(http_worker_t *worker, FILE *stream)
   }
 
   worker->range_header[0] = 0;
+  worker->content_length = -1;
 
   // Consume headers
   for(int i = 0; i < 50; i++) {
@@ -101,9 +105,12 @@ static void http_process(http_worker_t *worker, FILE *stream)
     if (line[0] == '\r' && line[1] == '\n')
       break;
 
-    if (strcasestr(line, "Range:") == line) {
+    if (strcasestr(line, HEADER_RANGE) == line) {
       strcpy(worker->range_header, line);
     }
+    if (strcasestr(line, HEADER_CONTENT_LENGTH) == line) {
+      worker->content_length = atoi(line + strlen(HEADER_CONTENT_LENGTH));
+    }
   }
 
   worker->current_method = NULL;

util/http/http.h

@@ -31,6 +31,7 @@ typedef struct http_worker_s {
   pthread_t thread;
 
   int client_fd;
+  int content_length;
   struct sockaddr_in client_addr;
   char *client_host;
   char client_method[BUFSIZE];
@@ -46,7 +47,9 @@ typedef struct http_server_options_s {
 
 int http_server(http_server_options_t *options, http_method_t *methods);
 void http_content(http_worker_t *worker, FILE *stream);
+void http_write_response(FILE *stream, const char *status, const char *content_type, const char *body, unsigned content_length);
 void http_200(FILE *stream, const char *data);
+void http_400(FILE *stream, const char *data);
 void http_404(FILE *stream, const char *data);
 void http_500(FILE *stream, const char *data);
 void *http_enum_params(http_worker_t *worker, FILE *stream, http_param_fn fn, void *opaque);

util/http/http_methods.c

@@ -3,7 +3,7 @@
 
 #include "http.h"
 
-static void http_write_response(
+void http_write_response(
   FILE *stream,
   const char *status,
   const char *content_type,
@@ -46,6 +46,11 @@ void http_200(FILE *stream, const char *data)
   http_write_response(stream, "200 OK", NULL, data ? data : "Nothing here.\n", 0);
 }
 
+void http_400(FILE *stream, const char *data)
+{
+  http_write_response(stream, "400 Bad Request", NULL, data ? data : "Nothing here.\n", 0);
+}
+
 void http_404(FILE *stream, const char *data)
 {
   http_write_response(stream, "404 Not Found", NULL, data ? data : "Nothing here.\n", 0);