dual streams (#467)

* dual streams

* dual streams

* dual streams

* dual streams

* use sdp transform

lib/utils/sdp-utils.js

@@ -1,7 +1,32 @@
+const sdpTransform = require('sdp-transform');
+
 const isOnhold = (sdp) => {
   return sdp && (sdp.includes('a=sendonly') || sdp.includes('a=inactive'));
 };
 
-module.exports = {
-  isOnhold
+const mergeSdpMedia = (sdp1, sdp2) => {
+  const parsedSdp1 = sdpTransform.parse(sdp1);
+  const parsedSdp2 = sdpTransform.parse(sdp2);
+
+  parsedSdp1.media.push(...parsedSdp2.media);
+  return sdpTransform.write(parsedSdp1);
+};
+
+const extractSdpMedia = (sdp) => {
+  const parsedSdp1 = sdpTransform.parse(sdp);
+  if (parsedSdp1.media.length > 1) {
+    parsedSdp1.media = [parsedSdp1.media[0]];
+    const parsedSdp2 = sdpTransform.parse(sdp);
+    parsedSdp2.media = [parsedSdp2.media[1]];
+
+    return [sdpTransform.write(parsedSdp1), sdpTransform.write(parsedSdp2)];
+  } else {
+    return [sdp, sdp];
+  }
+};
+
+module.exports = {
+  isOnhold,
+  mergeSdpMedia,
+  extractSdpMedia
 };