Android之WebRTC介紹(二)
WebRTC提供了點對點之間的通訊，但並不意味着WebRTC不須要服務器。暫且不說基於服務器的一些擴展業務，WebRTC至少有兩件事必需要用到服務器：
1. 瀏覽器之間交換創建通訊的元數據（信令）必須經過服務器
2. 爲了穿越NAT和防火牆
此處，咱們使用XMPP協議實現信令，採用openfire當作服務器，經過openfire服務器+Smack API實現信令的傳遞。
所以，在創建PeerConnection實例以後，想要使用其創建一個點對點的信道，咱們須要作兩件事：
1. 肯定本機上的媒體流的特性，好比分辨率、編解碼能力啥的（SDP描述符）
2. 鏈接兩端的主機的網絡地址（ICE Candidate）
經過offer和answer交換SDP描述符
大體上在兩個用戶（甲和乙）之間創建點對點鏈接流程應該是這個樣子（這裏不考慮錯誤的狀況，PeerConnection簡稱PC）：
甲和乙各自創建一個PC實例
甲經過PC所提供的createOffer()方法創建一個包含甲的SDP描述符的offer信令
甲經過PC所提供的setLocalDescription()方法，將甲的SDP描述符交給甲的PC實例
甲將offer信令經過服務器發送給乙
乙將甲的offer信令中所包含的的SDP描述符提取出來，經過PC所提供的setRemoteDescription()方法交給乙的PC實例
乙經過PC所提供的createAnswer()方法創建一個包含乙的SDP描述符answer信令
乙經過PC所提供的setLocalDescription()方法，將乙的SDP描述符交給乙的PC實例
乙將answer信令經過服務器發送給甲
甲接收到乙的answer信令後，將其中乙的SDP描述符提取出來，調用setRemoteDescripttion()方法交給甲本身的PC實例
經過在這一系列的信令交換以後，甲和乙所建立的PC實例都包含甲和乙的SDP描述符了，完成了兩件事的第一件。咱們還須要完成第二件事——獲取鏈接兩端主機的網絡地址
經過ICE框架創建NAT/防火牆穿越的鏈接
這個網絡地址應該是能從外界直接訪問，WebRTC使用ICE框架來得到這個地址。PeerConnection在創立的時候能夠將ICE服務器的地址傳遞進去，如：
private List<PeerConnection.IceServer> getIceServers(String url,String user,String credential)
{
PeerConnection.IceServer turn = new PeerConnection.IceServer(
url,user,credential);
LinkedList<PeerConnection.IceServer> iceServers = new LinkedList<PeerConnection.IceServer>();
iceServers.add(turn);
return iceServers;
}
//iceServer List對象獲取
List<PeerConnection.IceServer> iceServers = getIceServers(CoturnData.url,
CoturnData.userName,CoturnData.credential);
pcConstraints = new MediaConstraints();
pcConstraints.optional.add(new MediaConstraints.KeyValuePair(
"DtlsSrtpKeyAgreement", "true"));
pcConstraints.mandatory.add(new
MediaConstraints.KeyValuePair("VoiceActivityDetection", "false"));
pc = factory.createPeerConnection(iceServers,pcConstraints,pcObserver);
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固然這個地址也須要交換，仍是以甲乙兩位爲例，交換的流程以下（PeerConnection簡稱PC）：
甲、乙各建立配置了ICE服務器的PC實例，併爲其添加onicecandidate事件回調
當網絡候選可用時，將會調用onicecandidate函數
在回調函數內部，甲或乙將網絡候選的消息封裝在ICE Candidate信令中，經過服務器中轉，傳遞給對方
甲或乙接收到對方經過服務器中轉所發送過來ICE Candidate信令時，將其解析並得到網絡候選，將其經過PC實例的addIceCandidate()方法加入到PC實例中
這樣鏈接就創立完成了，能夠向RTCPeerConnection中經過addStream()加入流來傳輸媒體流數據。將流加入到RTCPeerConnection實例中後，對方就能夠經過onaddstream所綁定的回調函數監聽到了。調用addStream()能夠在鏈接完成以前，在鏈接創建以後，對方同樣能監聽到媒體流
代碼實現：
public class VideoCallActivity extends ParentActivity{
public static final String VIDEO_TRACK_ID = "video_track_id";
public static final String AUDIO_TRACK_ID = "audio_track_id";
public static final String LOCAL_MEDIA_STREAM_ID = "local_media_stream_id";
private String mServiceName; //XMPP服務器名稱
private GLSurfaceView mGLSurfaceView;
private GLSurfaceView mGLSurfaceViewRemote;
private PeerConnection pc;
private final PCObserver pcObserver = new PCObserver();
private final SDPObserver sdpObserver = new SDPObserver();
private MediaConstraints sdpMediaConstraints;
private MediaConstraints pcConstraints;
private String remoteName;
IceCandidate remoteIceCandidate;
private boolean mIsInited;
private boolean mIsCalled;
PeerConnectionFactory factory;
VideoCapturer videoCapturer;
VideoSource videoSource;
VideoRenderer localVideoRenderer;
VideoRenderer remoteVideoRenderer;
AudioManager audioManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_video_call);
//打開揚聲器
audioManager = (AudioManager) getSystemService(AUDIO_SERVICE);
audioManager.setSpeakerphoneOn(true);
mServiceName = connection.getServiceName();
mGLSurfaceView = (GLSurfaceView) findViewById(R.id.glsurfaceview);
// mGLSurfaceViewRemote = (GLSurfaceView) findViewById(R.id.glsurfaceview_remote);
//檢查初始化音視頻設備是否成功
if (!PeerConnectionFactory.initializeAndroidGlobals(this,true,true,true,null))
{
Log.e("init","PeerConnectionFactory init fail!");
return;
}
// Intent intent = getIntent().getBundleExtra()
//Media條件信息SDP接口
sdpMediaConstraints = new MediaConstraints();
//接受遠程音頻
sdpMediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
"OfferToReceiveAudio", "true"));
//接受遠程視頻
sdpMediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
"OfferToReceiveVideo", "true"));
factory = new PeerConnectionFactory();
//iceServer List對象獲取
List<PeerConnection.IceServer> iceServers = getIceServers(CoturnData.url,
CoturnData.userName,CoturnData.credential);
pcConstraints = new MediaConstraints();
pcConstraints.optional.add(new MediaConstraints.KeyValuePair(
"DtlsSrtpKeyAgreement", "true"));
pcConstraints.mandatory.add(new
MediaConstraints.KeyValuePair("VoiceActivityDetection", "false"));
pc = factory.createPeerConnection(iceServers,pcConstraints,pcObserver);
mIsInited = false;
mIsCalled=false;
boolean offer=getIntent().getBooleanExtra("createOffer",false);
//offer：若是offer爲true表示主叫方初始化，若是爲false表示被叫方初始化。
remoteName = getIntent().getStringExtra("remoteName");
if(!offer)
{
initialSystem();
}
else {
callRemote(remoteName);
}
//當VideoActivity已經打開時，處理後續的intent傳過來的數據。
processExtraData();
}
@Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
setIntent(intent);
processExtraData();
}
@Override
protected void onDestroy() {
super.onDestroy();
//通話結束，發送通話結束消息
videoCallEnded();
//釋放資源
videoCapturer.dispose();
videoSource.stop();
if (pc != null) {
pc.dispose();
pc = null;
}
audioManager.setSpeakerphoneOn(false);
}
private void videoCallEnded() {
String chatJid = remoteName+"@"+mServiceName;
Message message = new Message();
VideoInvitation videoInvitation = new VideoInvitation();
videoInvitation.setTypeText("video-ended");
message.addExtension(videoInvitation);
Chat chat = createChat(chatJid);
try {
chat.sendMessage(message);
} catch (SmackException.NotConnectedException e) {
e.printStackTrace();
}
}
private void processExtraData() {
Intent intent = getIntent();
//獲取SDP數據
String sdpType = intent.getStringExtra("type");
String sdpDescription = intent.getStringExtra("description");
if (sdpType != null)
{
SessionDescription.Type type = SessionDescription.Type.fromCanonicalForm(sdpType);
SessionDescription sdp = new SessionDescription(type,sdpDescription);
if (pc == null)
{
Log.e("pc","pc == null");
}
pc.setRemoteDescription(sdpObserver,sdp);
//若是是offer,則被叫方createAnswer
if (sdpType.equals("offer"))
{
mIsCalled = true;
pc.createAnswer(sdpObserver,sdpMediaConstraints);
}
}
//獲取ICE Candidate數據
String iceSdpMid = intent.getStringExtra("sdpMid");
int iceSdpMLineIndex = intent.getIntExtra("sdpMLineIndex",-1);
String iceSdp = intent.getStringExtra("sdp");
if (iceSdpMid != null)
{
IceCandidate iceCandidate = new IceCandidate(iceSdpMid,iceSdpMLineIndex,iceSdp);
if (remoteIceCandidate == null)
{
remoteIceCandidate = iceCandidate;
}
//下面這步放到函數drainRemoteCandidates()中
/*//添加遠端的IceCandidate到pc
pc.addIceCandidate(iceCandidate);*/
}
//結束activity
boolean videoEnded = intent.getBooleanExtra("videoEnded",false);
if (videoEnded)
{
finish();
}
}
private void callRemote(String remoteName) {
initialSystem();
//createOffer
pc.createOffer(sdpObserver,sdpMediaConstraints);
}
private void initialSystem() {
if (mIsInited)
{
return;
}
//獲取前置攝像頭本地視頻流
String frontDeviceName = VideoCapturerAndroid.getNameOfFrontFacingDevice();
// String frontDeviceName = "Camera 1, Facing front, Orientation 0";
Log.e("CameraName","CameraName: "+frontDeviceName);
videoCapturer = VideoCapturerAndroid.create(frontDeviceName);
if (videoCapturer == null)
{
Log.e("open","fail to open camera");
return;
}
//視頻
MediaConstraints mediaConstraints = new MediaConstraints();
videoSource = factory.createVideoSource(videoCapturer, mediaConstraints);
VideoTrack localVideoTrack = factory.createVideoTrack(VIDEO_TRACK_ID, videoSource);
//音頻
MediaConstraints audioConstraints = new MediaConstraints();
AudioSource audioSource = factory.createAudioSource(audioConstraints);
AudioTrack localAudioTrack = factory.createAudioTrack(AUDIO_TRACK_ID,audioSource);
Runnable runnable = new Runnable() {
@Override
public void run() {
}
};
VideoRendererGui.setView(mGLSurfaceView,runnable);
try {
//改爲ScalingType.SCALE_ASPECT_FILL能夠顯示雙方視頻，可是顯示比例不美觀，而且不知道最後一個參數true和false的含義。
localVideoRenderer = VideoRendererGui.createGui(0,0,30,30, VideoRendererGui.ScalingType.SCALE_ASPECT_FILL,true);
remoteVideoRenderer = VideoRendererGui.createGui(0,0,100,100, VideoRendererGui.ScalingType.SCALE_FILL,true);
localVideoTrack.addRenderer(localVideoRenderer);
} catch (Exception e) {
e.printStackTrace();
}
MediaStream localMediaStream = factory.createLocalMediaStream(LOCAL_MEDIA_STREAM_ID);
localMediaStream.addTrack(localAudioTrack);
localMediaStream.addTrack(localVideoTrack);
pc.addStream(localMediaStream);
}
private List<PeerConnection.IceServer> getIceServers(String url,String user,String credential)
{
PeerConnection.IceServer turn = new PeerConnection.IceServer(
url,user,credential);
LinkedList<PeerConnection.IceServer> iceServers = new LinkedList<PeerConnection.IceServer>();
iceServers.add(turn);
return iceServers;
}
private class PCObserver implements PeerConnection.Observer
{
@Override
public void onSignalingChange(PeerConnection.SignalingState signalingState) {
}
@Override
public void onIceConnectionChange(PeerConnection.IceConnectionState iceConnectionState) {
}
@Override
public void onIceGatheringChange(PeerConnection.IceGatheringState iceGatheringState) {
}
//發送ICE候選到其餘客戶端
@Override
public void onIceCandidate(final IceCandidate iceCandidate) {
//利用XMPP發送iceCandidate到其餘客戶端
runOnUiThread(new Runnable() {
@Override
public void run() {
String chatJid = remoteName+"@"+mServiceName;
Message message = new Message();
IceCandidateExtensionElement iceCandidateExtensionElement=
new IceCandidateExtensionElement();
iceCandidateExtensionElement.setSdpMidText(iceCandidate.sdpMid);
iceCandidateExtensionElement.setSdpMLineIndexText(iceCandidate.sdpMLineIndex);
iceCandidateExtensionElement.setSdpText(iceCandidate.sdp);
message.addExtension(iceCandidateExtensionElement);
Chat chat = createChat(chatJid);
try {
chat.sendMessage(message);
} catch (SmackException.NotConnectedException e) {
e.printStackTrace();
}
}
});
}
//Display a media stream from remote
@Override
public void onAddStream(final MediaStream mediaStream) {
runOnUiThread(new Runnable() {
@Override
public void run() {
if (pc == null)
{
Log.e("onAddStream","pc == null");
return;
}
if (mediaStream.videoTracks.size()>1 || mediaStream.audioTracks.size()>1)
{
Log.e("onAddStream","size > 1");
return;
}
if (mediaStream.videoTracks.size() == 1)
{
VideoTrack videoTrack = mediaStream.videoTracks.get(0);
videoTrack.addRenderer(remoteVideoRenderer);
}
}
});
}
@Override
public void onRemoveStream(final MediaStream mediaStream) {
runOnUiThread(new Runnable() {
@Override
public void run() {
mediaStream.videoTracks.get(0).dispose();
}
});
}
@Override
public void onDataChannel(DataChannel dataChannel) {
}
@Override
public void onRenegotiationNeeded() {
}
}
private class SDPObserver implements SdpObserver
{
@Override
public void onCreateSuccess(final SessionDescription sessionDescription) {
//sendMessage(offer);
runOnUiThread(new Runnable() {
@Override
public void run() {
String chatJid = remoteName+"@"+mServiceName;
Message message = new Message();
SDPExtensionElement sdpExtensionElement = new SDPExtensionElement();
sdpExtensionElement.setTypeText(sessionDescription.type.canonicalForm());
sdpExtensionElement.setDescriptionText(sessionDescription.description);
message.addExtension(sdpExtensionElement);
Chat chat = createChat(chatJid);
try {
chat.sendMessage(message);
} catch (SmackException.NotConnectedException e) {
e.printStackTrace();
}
pc.setLocalDescription(sdpObserver,sessionDescription);
}
});
}
@Override
public void onSetSuccess() {
runOnUiThread(new Runnable() {
@Override
public void run() {
//主叫方
if (!mIsCalled)
{
if (pc.getRemoteDescription() != null)
{
drainRemoteCandidates();
}
}
//被叫方
else
{
//若是被叫方尚未createAnswer
if (pc.getLocalDescription() == null)
{
Log.e("SDPObserver", "SDPObserver create answer");
}
else
{
drainRemoteCandidates();
}
}
}
});
}
private void drainRemoteCandidates() {
if (remoteIceCandidate == null)
{
Log.e("SDPObserver","remoteIceCandidate == null");
return;
}
pc.addIceCandidate(remoteIceCandidate);
Log.e("IceCanditate","添加IceCandidate成功");
remoteIceCandidate = null;
}
@Override
public void onCreateFailure(String s) {
Log.e("SDPObserver","onCreateFailure");
}
@Override
public void onSetFailure(String s) {
Log.e("SDPObserver","onSetFailure");
}
}
}
————————————————
版權聲明：本文爲CSDN博主「程序員的自我救贖」的原創文章，遵循 CC 4.0 BY-SA 版權協議，轉載請附上原文出處連接及本聲明。
原文連接：https://blog.csdn.net/u011026329/article/details/50582690
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