From a22c48c4ca34e245a67d3c19deb4b4ea3ef8a802 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miroslav=20=C5=A0ediv=C3=BD?= <sedivy.miro@gmail.com>
Date: Fri, 20 Jan 2023 23:09:01 +0100
Subject: [PATCH] WebRTC latency in stats (#20)

* webrtc stats full report.

* add ping+pong latency counter.

* single console log.

* remove report & add latency to webrtc stats.

* fix.
---
 src/component/internal/webrtc.ts | 32 ++++++++++++++++++++++++++++++++
 src/component/types/webrtc.ts    |  3 +++
 src/page/components/events.vue   | 14 ++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/src/component/internal/webrtc.ts b/src/component/internal/webrtc.ts
index 1a0cec9c..cdd1522f 100644
--- a/src/component/internal/webrtc.ts
+++ b/src/component/internal/webrtc.ts
@@ -3,6 +3,8 @@ import { WebRTCStats, CursorPosition, CursorImage } from '../types/webrtc'
 import { Logger } from '../utils/logger'
 import { videoSnap } from '../utils/video-snap'
 
+const maxUint32 = 2 ** 32 - 1
+
 export const OPCODE = {
   MOVE: 0x01,
   SCROLL: 0x02,
@@ -10,6 +12,7 @@ export const OPCODE = {
   KEY_UP: 0x04,
   BTN_DOWN: 0x05,
   BTN_UP: 0x06,
+  PING: 0x07,
 } as const
 
 export interface ICEServer {
@@ -44,6 +47,8 @@ export class NekoWebRTC extends EventEmitter<NekoWebRTCEvents> {
   private _connected = false
   private _candidates: RTCIceCandidateInit[] = []
   private _statsStop?: () => void
+  private _requestLatency = 0
+  private _responseLatency = 0
 
   // eslint-disable-next-line
   constructor(
@@ -340,6 +345,7 @@ export class NekoWebRTC extends EventEmitter<NekoWebRTCEvents> {
 
   public send(event: 'wheel' | 'mousemove', data: { x: number; y: number }): void
   public send(event: 'mousedown' | 'mouseup' | 'keydown' | 'keyup', data: { key: number }): void
+  public send(event: 'ping', data: number): void
   public send(event: string, data: any): void {
     if (typeof this._channel === 'undefined' || this._channel.readyState !== 'open') {
       this._log.warn(`attempting to send data, but data-channel is not open`, { event })
@@ -393,6 +399,14 @@ export class NekoWebRTC extends EventEmitter<NekoWebRTCEvents> {
         payload.setUint16(1, 4)
         payload.setUint32(3, data.key)
         break
+      case 'ping':
+        buffer = new ArrayBuffer(11)
+        payload = new DataView(buffer)
+        payload.setUint8(0, OPCODE.PING)
+        payload.setUint16(1, 8)
+        payload.setUint32(3, Math.trunc(data / maxUint32))
+        payload.setUint32(7, data % maxUint32)
+        break
       default:
         this._log.warn(`unknown data event`, { event })
         return
@@ -457,6 +471,18 @@ export class NekoWebRTC extends EventEmitter<NekoWebRTCEvents> {
         }
         reader.readAsDataURL(blob)
 
+        break
+      case 3:
+        const nowTs = Date.now()
+
+        const [clientTs1, clientTs2] = [payload.getUint32(3), payload.getUint32(7)]
+        const clientTs = clientTs1 * maxUint32 + clientTs2
+        const [serverTs1, serverTs2] = [payload.getUint32(11), payload.getUint32(15)]
+        const serverTs = serverTs1 * maxUint32 + serverTs2
+
+        this._requestLatency = serverTs - clientTs
+        this._responseLatency = nowTs - serverTs
+
         break
       default:
         this._log.warn(`unhandled webrtc event`, { event, payload })
@@ -534,6 +560,10 @@ export class NekoWebRTC extends EventEmitter<NekoWebRTCEvents> {
           width: report.frameWidth || NaN,
           height: report.frameHeight || NaN,
           muted: this._track?.muted,
+          // latency from ping/pong messages
+          latency: this._requestLatency + this._responseLatency,
+          requestLatency: this._requestLatency,
+          responseLatency: this._responseLatency,
         })
       }
 
@@ -542,6 +572,8 @@ export class NekoWebRTC extends EventEmitter<NekoWebRTCEvents> {
       framesDecoded = report.framesDecoded
       packetsLost = report.packetsLost
       packetsReceived = report.packetsReceived
+
+      this.send('ping', Date.now())
     }, ms)
 
     return function () {
diff --git a/src/component/types/webrtc.ts b/src/component/types/webrtc.ts
index bedc243c..7059b86c 100644
--- a/src/component/types/webrtc.ts
+++ b/src/component/types/webrtc.ts
@@ -6,6 +6,9 @@ export interface WebRTCStats {
   width: number
   height: number
   muted?: boolean
+  latency: number
+  requestLatency: number
+  responseLatency: number
 }
 
 export interface CursorPosition {
diff --git a/src/page/components/events.vue b/src/page/components/events.vue
index 0733dd7d..6d75abb4 100644
--- a/src/page/components/events.vue
+++ b/src/page/components/events.vue
@@ -109,6 +109,20 @@
               <th style="width: 40%">bitrate</th>
               <td>{{ Math.floor(neko.state.connection.webrtc.stats.bitrate / 1024 / 8) }} KB/s</td>
             </tr>
+            <tr>
+              <th style="width: 40%">latency</th>
+              <td
+                :title="
+                  'request: ' +
+                  neko.state.connection.webrtc.stats.requestLatency +
+                  'ms, response: ' +
+                  neko.state.connection.webrtc.stats.responseLatency +
+                  'ms'
+                "
+              >
+                {{ neko.state.connection.webrtc.stats.latency }}ms
+              </td>
+            </tr>
             <tr>
               <th>loss</th>
               <td :style="neko.state.connection.webrtc.stats.packetLoss >= 1 ? 'background: red' : ''">