Display active tracks in OTel metrics (#1085)

* Add track, feed and transceiver spans under call span

src/otel/OTelCallFeedMediaStreamSpan.ts

@@ -0,0 +1,57 @@
+import { Span } from "@opentelemetry/api";
+import {
+  CallFeedStats,
+  TrackStats,
+} from "matrix-js-sdk/src/webrtc/stats/statsReport";
+
+import { ElementCallOpenTelemetry } from "./otel";
+import { OTelCallAbstractMediaStreamSpan } from "./OTelCallAbstractMediaStreamSpan";
+
+export class OTelCallFeedMediaStreamSpan extends OTelCallAbstractMediaStreamSpan {
+  private readonly prev: { isAudioMuted: boolean; isVideoMuted: boolean };
+
+  constructor(
+    readonly oTel: ElementCallOpenTelemetry,
+    readonly callSpan: Span,
+    callFeed: CallFeedStats
+  ) {
+    const postFix =
+      callFeed.type === "local" && callFeed.prefix === "from-call-feed"
+        ? "(clone)"
+        : "";
+    super(oTel, callSpan, `matrix.call.feed.${callFeed.type}${postFix}`);
+    this.span.setAttribute("feed.streamId", callFeed.stream);
+    this.span.setAttribute("feed.type", callFeed.type);
+    this.span.setAttribute("feed.readFrom", callFeed.prefix);
+    this.span.setAttribute("feed.purpose", callFeed.purpose);
+    this.prev = {
+      isAudioMuted: callFeed.isAudioMuted,
+      isVideoMuted: callFeed.isVideoMuted,
+    };
+    this.span.addEvent("matrix.call.feed.initState", this.prev);
+  }
+
+  public update(callFeed: CallFeedStats): void {
+    if (this.prev.isAudioMuted !== callFeed.isAudioMuted) {
+      this.span.addEvent("matrix.call.feed.audioMuted", {
+        isAudioMuted: callFeed.isAudioMuted,
+      });
+      this.prev.isAudioMuted = callFeed.isAudioMuted;
+    }
+    if (this.prev.isVideoMuted !== callFeed.isVideoMuted) {
+      this.span.addEvent("matrix.call.feed.isVideoMuted", {
+        isVideoMuted: callFeed.isVideoMuted,
+      });
+      this.prev.isVideoMuted = callFeed.isVideoMuted;
+    }
+
+    const trackStats: TrackStats[] = [];
+    if (callFeed.video) {
+      trackStats.push(callFeed.video);
+    }
+    if (callFeed.audio) {
+      trackStats.push(callFeed.audio);
+    }
+    this.upsertTrackSpans(trackStats);
+  }
+}