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copied!<p>While testing <strong>WebRTC</strong>, I found that such condition occurs when we call <code>peerConnection.addStream(…)</code> in the <strong>wrong</strong> place ---- </p> <p><em>You must remember that ordering highly matters in <strong>WebRTC</strong>!</em></p> <hr> <h3>Updated at: 6:36 PM - Thursday, July 17, 2014 (UTC)</h3> <p>Blank video occurs in following cases:</p> <ol> <li>You're using STUN whilst your SSL certificate is either expired or it has invalid entries.</li> <li>You're using STUN however it is corporate firewall, or hospital network or private network which is blocking or hiding external ip addresses or some ports.</li> <li>Both peers has invalid sendrecv/sendonly/recvonly pairs</li> <li>Offerer didn't attach the stream or it is Firefox which fails in cases when user attached only audio stream however you're using <code>OfferToReceiveVideo:true</code></li> <li>You're checking for <code>HTMLMediaElement.HAVE_CURRENT_DATA</code> or <code>mediaElement.paused</code> or <code>mediaElement.currentTime</code> whilst it is android which has known issues regarding these properties.</li> </ol> <h2>Solutions?</h2> <ol> <li>Use TURN from XirSys or <a href="https://code.google.com/p/rfc5766-turn-server/" rel="noreferrer">install your own</a>.</li> <li>Make sure that you're using valid SSL certificate or use HTTP instead.</li> <li>Make sure that offerer attached the stream; also make sure that <code>OfferToReceiveAudio</code>/<code>OfferToReceiveVideo</code> are used according to stream(s) attached.</li> <li>Make sure that you didn't modify the SDP; also try to compare SDP between both peers and find-out mismatches.</li> </ol> <p>Ordering of the code is, kind of rare-issues, nowadays, because we all know that <code>addStream</code> should be called before creating offer or answer; even for renegotiated sessions.</p> <p>Try to use <code>chrome://webrtc-internals</code> and Firefox's <code>about:config</code> to see what's happening inside these browsers; and always use console-logs for <code>onIceConnectionStateChange</code> event which helps you check if ICE-Agent <code>failed</code> in the ICE-connectivity check process or...</p> <p>Sometimes setting-remote-sdp for offerer too earlier, causes exceptions. Always use <code>onSdpError</code> both for <code>createOffer</code>/<code>createAnswer</code> and <code>setLocalDescription</code>/<code>setRemoteDescription</code> e.g.</p> <p><code>peer.setRemoteDescription(remoteSDP, onSdpSuccess, onSdpFailure); </code></p> <hr> <p>A few demos resources:</p> <ol> <li><a href="https://github.com/muaz-khan/WebRTC-Experiment" rel="noreferrer">https://github.com/muaz-khan/WebRTC-Experiment</a> / <a href="https://www.webrtc-experiment.com/" rel="noreferrer">Demos</a></li> <li><a href="https://github.com/mozilla/webrtc-landing" rel="noreferrer">https://github.com/mozilla/webrtc-landing</a></li> </ol> <p>and <a href="https://www.webrtc-experiment.com/docs/TURN-server-installation-guide.html" rel="noreferrer">https://www.webrtc-experiment.com/docs/TURN-server-installation-guide.html</a></p>

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