Как передать картинку в stream если не работает камера?

Question

[xa4ik0003285]

Есть простое приложение, позволяющее вести одноранговые видеочаты.

Код

(function() {
      /** @type {SocketIOClient.Socket} */
      const socket = io.connect(window.location.origin);
      const localVideo = document.querySelector('.localVideo');
      const remoteVideos = document.querySelector('.remoteVideos');
      const peerConnections = {};
      
      let room = !location.pathname.substring(1) ? 'home' : location.pathname.substring(1);
      let getUserMediaAttempts = 5;
      let gettingUserMedia = false;
    
      /** @type {RTCConfiguration} */
      const config = {
        'iceServers': [{
          'urls': ['stun:stun.l.google.com:19302']
        }]
      };
    
      /** @type {MediaStreamConstraints} */
      const constraints = {
        // audio: true,
        video: { facingMode: "user" }
      };
    
      socket.on('full', function(room) {
        alert('Room ' + room + ' is full');
      });
    
      socket.on('bye', function(id) {
        handleRemoteHangup(id);
      });
    
      if (room && !!room) {
        socket.emit('join', room);
      }
    
      window.onunload = window.onbeforeunload = function() {
        socket.close();
      };
    
      socket.on('ready', function (id) {
        if (!(localVideo instanceof HTMLVideoElement) || !localVideo.srcObject) {
          return;
        }
        const peerConnection = new RTCPeerConnection(config);
        peerConnections[id] = peerConnection;
        if (localVideo instanceof HTMLVideoElement) {
          peerConnection.addStream(localVideo.srcObject);
        }
        peerConnection.createOffer()
        .then(sdp => peerConnection.setLocalDescription(sdp))
        .then(function () {
          socket.emit('offer', id, peerConnection.localDescription);
        });
        peerConnection.onaddstream = event => handleRemoteStreamAdded(event.stream, id);
        peerConnection.onicecandidate = function(event) {
          if (event.candidate) {
            socket.emit('candidate', id, event.candidate);
          }
        };
      });
    
      socket.on('offer', function(id, description) {
        const peerConnection = new RTCPeerConnection(config);
        peerConnections[id] = peerConnection;
        if (localVideo instanceof HTMLVideoElement) {
          peerConnection.addStream(localVideo.srcObject);
        }
        peerConnection.setRemoteDescription(description)
        .then(() => peerConnection.createAnswer())
        .then(sdp => peerConnection.setLocalDescription(sdp))
        .then(function () {
          socket.emit('answer', id, peerConnection.localDescription);
        });
        peerConnection.onaddstream = event => handleRemoteStreamAdded(event.stream, id);
        peerConnection.onicecandidate = function(event) {
          if (event.candidate) {
            socket.emit('candidate', id, event.candidate);
          }
        };
      });
    
      socket.on('candidate', function(id, candidate) {
        peerConnections[id].addIceCandidate(new RTCIceCandidate(candidate))
        .catch(e => console.error(e));
      });
    
      socket.on('answer', function(id, description) {
        peerConnections[id].setRemoteDescription(description);
      });
    
      function getUserMediaSuccess(stream) {
        gettingUserMedia = false;
        if (localVideo instanceof HTMLVideoElement) {
          !localVideo.srcObject && (localVideo.srcObject = stream);
        }
        socket.emit('ready');
      }
    
      function handleRemoteStreamAdded(stream, id) {
        const remoteVideo = document.createElement('video');
        remoteVideo.srcObject = stream;
        remoteVideo.setAttribute("id", id.replace(/[^a-zA-Z]+/g, "").toLowerCase());
        remoteVideo.setAttribute("playsinline", "true");
        remoteVideo.setAttribute("autoplay", "true");
        remoteVideos.appendChild(remoteVideo);
        if (remoteVideos.querySelectorAll("video").length === 1) {
          remoteVideos.setAttribute("class", "one remoteVideos");
        } else {
          remoteVideos.setAttribute("class", "remoteVideos");
        }
      }
    
      function getUserMediaError(error) {
        console.error(error);
        gettingUserMedia = false;
        (--getUserMediaAttempts > 0) && setTimeout(getUserMediaDevices, 1000);
      }
    
      function getUserMediaDevices() {
        if (localVideo instanceof HTMLVideoElement) {
          if (localVideo.srcObject) {
            getUserMediaSuccess(localVideo.srcObject);
          } else if (!gettingUserMedia && !localVideo.srcObject) {
            gettingUserMedia = true;
            navigator.mediaDevices.getUserMedia(constraints)
            .then(getUserMediaSuccess)
            .catch(getUserMediaError);
          }
        }
      }
    
      function handleRemoteHangup(id) {
        peerConnections[id] && peerConnections[id].close();
        delete peerConnections[id];
        document.querySelector("#" + id.replace(/[^a-zA-Z]+/g, "").toLowerCase()).remove();
        if (remoteVideos.querySelectorAll("video").length === 1) {
          remoteVideos.setAttribute("class", "one remoteVideos");
        } else {
          remoteVideos.setAttribute("class", "remoteVideos");
        }
      }
    
      getUserMediaDevices();
    })();

Все работает, но я не знаю, как исправить код, чтобы чат работал, даже если у одного из пользователей не работает камера