Add latency compensator to player. Closes #1931

web/components/video/OwncastPlayer.tsx

@@ -8,12 +8,17 @@ import { getLocalStorage, setLocalStorage } from '../../utils/localStorage';
 import { isVideoPlayingAtom, clockSkewAtom } from '../stores/ClientConfigStore';
 import PlaybackMetrics from './metrics/playback';
 import createVideoSettingsMenuButton from './settings-menu';
+import LatencyCompensator from './latencyCompensator';
 
 const VIDEO_CONFIG_URL = '/api/video/variants';
 const PLAYER_VOLUME = 'owncast_volume';
+const LATENCY_COMPENSATION_ENABLED = 'latencyCompensatorEnabled';
 
 const ping = new ViewerPing();
 let playbackMetrics = null;
+let latencyCompensator = null;
+let latencyCompensatorEnabled = false;
+
 interface Props {
   source: string;
   online: boolean;
@@ -73,6 +78,50 @@ export default function OwncastPlayer(props: Props) {
     }
   };
 
+  const setLatencyCompensatorItemTitle = title => {
+    const item = document.querySelector('.latency-toggle-item > .vjs-menu-item-text');
+    if (!item) {
+      return;
+    }
+
+    item.innerHTML = title;
+  };
+
+  const startLatencyCompensator = () => {
+    if (latencyCompensator) {
+      latencyCompensator.stop();
+    }
+
+    latencyCompensatorEnabled = true;
+
+    latencyCompensator = new LatencyCompensator(playerRef.current);
+    latencyCompensator.setClockSkew(clockSkew);
+    latencyCompensator.enable();
+    setLocalStorage(LATENCY_COMPENSATION_ENABLED, true);
+
+    setLatencyCompensatorItemTitle('disable minimized latency');
+  };
+
+  const stopLatencyCompensator = () => {
+    if (latencyCompensator) {
+      latencyCompensator.disable();
+    }
+    latencyCompensator = null;
+    latencyCompensatorEnabled = false;
+    setLocalStorage(LATENCY_COMPENSATION_ENABLED, false);
+    setLatencyCompensatorItemTitle(
+      '<span style="font-size: 0.8em">enable minimized latency (experimental)</span>',
+    );
+  };
+
+  const toggleLatencyCompensator = () => {
+    if (latencyCompensatorEnabled) {
+      stopLatencyCompensator();
+    } else {
+      startLatencyCompensator();
+    }
+  };
+
   // Register keyboard shortcut for the space bar to toggle playback
   useHotkeys('space', togglePlayback, {
     enableOnContentEditable: false,
@@ -133,6 +182,23 @@ export default function OwncastPlayer(props: Props) {
     playerRef.current = player;
     setSavedVolume();
 
+    const setupLatencyCompensator = () => {
+      const tech = player.tech({ IWillNotUseThisInPlugins: true });
+
+      // VHS is required.
+      if (!tech || !tech.vhs) {
+        return;
+      }
+
+      const latencyCompensatorEnabledSaved = getLocalStorage(LATENCY_COMPENSATION_ENABLED);
+
+      if (latencyCompensatorEnabledSaved === 'true' && tech && tech.vhs) {
+        startLatencyCompensator();
+      } else {
+        stopLatencyCompensator();
+      }
+    };
+
     // You can handle player events here, for example:
     player.on('waiting', () => {
       player.log('player is waiting');
@@ -170,14 +236,19 @@ export default function OwncastPlayer(props: Props) {
 
     const createSettings = async () => {
       const videoQualities = await getVideoSettings();
-      const menuButton = createVideoSettingsMenuButton(player, videojs, videoQualities);
+      const menuButton = createVideoSettingsMenuButton(
+        player,
+        videojs,
+        videoQualities,
+        toggleLatencyCompensator,
+      );
       player.controlBar.addChild(
         menuButton,
         {},
         // eslint-disable-next-line no-underscore-dangle
         player.controlBar.children_.length - 2,
       );
-      // this.latencyCompensatorToggleButton = lowLatencyItem;
+      setupLatencyCompensator();
     };
 
     createSettings();

web/components/video/latencyCompensator.js

@@ -44,6 +44,28 @@ const MAX_JUMP_FREQUENCY = 20 * 1000; // How often we'll allow a time jump.
 const MAX_ACTIONABLE_LATENCY = 80 * 1000; // If latency is seen to be greater than this then something is wrong.
 const STARTUP_WAIT_TIME = 10 * 1000; // The amount of time after we start up that we'll allow monitoring to occur.
 
+function getCurrentlyPlayingSegment(tech) {
+  const targetMedia = tech.vhs.playlists.media();
+  const snapshotTime = tech.currentTime();
+  let segment;
+
+  // Iterate trough available segments and get first within which snapshot_time is
+  // eslint-disable-next-line no-plusplus
+  for (let i = 0, l = targetMedia.segments.length; i < l; i++) {
+    // Note: segment.end may be undefined or is not properly set
+    if (snapshotTime < targetMedia.segments[i].end) {
+      segment = targetMedia.segments[i];
+      break;
+    }
+  }
+
+  if (!segment) {
+    [segment] = targetMedia.segments;
+  }
+
+  return segment;
+}
+
 class LatencyCompensator {
   constructor(player) {
     this.player = player;
@@ -143,10 +165,12 @@ class LatencyCompensator {
         return;
       }
 
-      tech.vhs.stats.buffered.forEach((buffer) => {
+      tech.vhs.stats.buffered.forEach(buffer => {
         totalBuffered += buffer.end - buffer.start;
       });
-    } catch (e) {}
+    } catch (e) {
+      console.error(e);
+    }
 
     // Determine how much of the current playlist's bandwidth requirements
     // we're utilizing. If it's too high then we can't afford to push
@@ -164,10 +188,7 @@ class LatencyCompensator {
 
       // If we're downloading media fast enough or we feel like we have a large
       // enough buffer then continue. Otherwise timeout for a bit.
-      if (
-        bandwidthRatio < REQUIRED_BANDWIDTH_RATIO &&
-        totalBuffered < segment.duration * 6
-      ) {
+      if (bandwidthRatio < REQUIRED_BANDWIDTH_RATIO && totalBuffered < segment.duration * 6) {
         this.timeout();
         return;
       }
@@ -175,30 +196,24 @@ class LatencyCompensator {
       // How far away from live edge do we stop the compensator.
       const computedMinLatencyThreshold = Math.max(
         MIN_LATENCY,
-        segment.duration * 1000 * LOWEST_LATENCY_SEGMENT_LENGTH_MULTIPLIER
+        segment.duration * 1000 * LOWEST_LATENCY_SEGMENT_LENGTH_MULTIPLIER,
       );
 
       // Create an array of all the buffering events in the past along with
       // the computed min latency above.
-      const targetLatencies = this.bufferedAtLatency.concat([
-        computedMinLatencyThreshold,
-      ]);
+      const targetLatencies = this.bufferedAtLatency.concat([computedMinLatencyThreshold]);
 
       // Determine if we need to reduce the minimum latency we computed
       // above based on buffering events that have taken place in the past by
       // creating an array of all the buffering events and the above computed
       // minimum latency target and averaging all those values.
       const minLatencyThreshold =
-        targetLatencies.reduce((sum, current) => sum + current, 0) /
-        targetLatencies.length;
+        targetLatencies.reduce((sum, current) => sum + current, 0) / targetLatencies.length;
 
       // How far away from live edge do we start the compensator.
       let maxLatencyThreshold = Math.max(
         minLatencyThreshold * 1.4,
-        Math.min(
-          segment.duration * 1000 * HIGHEST_LATENCY_SEGMENT_LENGTH_MULTIPLIER,
-          MAX_LATENCY
-        )
+        Math.min(segment.duration * 1000 * HIGHEST_LATENCY_SEGMENT_LENGTH_MULTIPLIER, MAX_LATENCY),
       );
 
       // If this newly adjusted minimum latency ends up being greater than
@@ -228,10 +243,7 @@ class LatencyCompensator {
       if (latency > maxLatencyThreshold) {
         // If the current latency exceeds the max jump amount then
         // force jump into the future, skipping all the video in between.
-        if (
-          this.shouldJumpToLive() &&
-          latency > maxLatencyThreshold + MAX_JUMP_LATENCY
-        ) {
+        if (this.shouldJumpToLive() && latency > maxLatencyThreshold + MAX_JUMP_LATENCY) {
           const jumpAmount = latency / 1000 - segment.duration * 3;
           const seekPosition = this.player.currentTime() + jumpAmount;
           console.info(
@@ -242,17 +254,13 @@ class LatencyCompensator {
             'to live from ',
             this.player.currentTime(),
             ' to ',
-            seekPosition
+            seekPosition,
           );
 
           // Verify we have the seek position buffered before jumping.
           const availableBufferedTimeEnd = tech.vhs.stats.buffered[0].end;
           const availableBufferedTimeStart = tech.vhs.stats.buffered[0].start;
-          if (
-            seekPosition >
-            availableBufferedTimeStart <
-            availableBufferedTimeEnd
-          ) {
+          if (seekPosition > availableBufferedTimeStart < availableBufferedTimeEnd) {
             this.jump(seekPosition);
 
             return;
@@ -260,13 +268,10 @@ class LatencyCompensator {
         }
 
         // Using our bandwidth ratio determine a wide guess at how fast we can play.
-        var proposedPlaybackRate = bandwidthRatio * 0.33;
+        let proposedPlaybackRate = bandwidthRatio * 0.33;
 
         // But limit the playback rate to a max value.
-        proposedPlaybackRate = Math.max(
-          Math.min(proposedPlaybackRate, MAX_SPEEDUP_RATE),
-          1.0
-        );
+        proposedPlaybackRate = Math.max(Math.min(proposedPlaybackRate, MAX_SPEEDUP_RATE), 1.0);
 
         if (proposedPlaybackRate > this.playbackRate + MAX_SPEEDUP_RAMP) {
           // If this proposed speed is substantially faster than the current rate,
@@ -275,8 +280,7 @@ class LatencyCompensator {
         }
 
         // Limit to 3 decimal places of precision.
-        proposedPlaybackRate =
-          Math.round(proposedPlaybackRate * Math.pow(10, 3)) / Math.pow(10, 3);
+        proposedPlaybackRate = Math.round(proposedPlaybackRate * 10 ** 3) / 10 ** 3;
 
         // Otherwise start the playback rate adjustment.
         this.start(proposedPlaybackRate);
@@ -300,7 +304,7 @@ class LatencyCompensator {
         'skew: ',
         this.clockSkewMs,
         'rebuffer events: ',
-        this.bufferingCounter
+        this.bufferingCounter,
       );
     } catch (err) {
       // console.error(err);
@@ -325,12 +329,7 @@ class LatencyCompensator {
 
     this.lastJumpOccurred = new Date();
 
-    console.info(
-      'current time',
-      this.player.currentTime(),
-      'seeking to',
-      seekPosition
-    );
+    console.info('current time', this.player.currentTime(), 'seeking to', seekPosition);
     this.player.currentTime(seekPosition);
 
     setTimeout(() => {
@@ -435,7 +434,7 @@ class LatencyCompensator {
     this.disable();
   }
 
-  handleError(e) {
+  handleError() {
     if (!this.enabled) {
       return;
     }
@@ -444,7 +443,7 @@ class LatencyCompensator {
   }
 
   countBufferingEvent() {
-    this.bufferingCounter++;
+    this.bufferingCounter += 1;
 
     if (this.bufferingCounter > REBUFFER_EVENT_LIMIT) {
       this.disable();
@@ -457,13 +456,13 @@ class LatencyCompensator {
       'latency compensation timeout due to buffering:',
       this.bufferingCounter,
       'buffering events of',
-      REBUFFER_EVENT_LIMIT
+      REBUFFER_EVENT_LIMIT,
     );
 
     // Allow us to forget about old buffering events if enough time goes by.
     setTimeout(() => {
       if (this.bufferingCounter > 0) {
-        this.bufferingCounter--;
+        this.bufferingCounter -= 1;
       }
     }, BUFFERING_AMNESTY_DURATION);
   }
@@ -487,26 +486,4 @@ class LatencyCompensator {
   }
 }
 
-function getCurrentlyPlayingSegment(tech) {
-  var target_media = tech.vhs.playlists.media();
-  var snapshot_time = tech.currentTime();
-
-  var segment;
-
-  // Iterate trough available segments and get first within which snapshot_time is
-  for (var i = 0, l = target_media.segments.length; i < l; i++) {
-    // Note: segment.end may be undefined or is not properly set
-    if (snapshot_time < target_media.segments[i].end) {
-      segment = target_media.segments[i];
-      break;
-    }
-  }
-
-  if (!segment) {
-    segment = target_media.segments[0];
-  }
-
-  return segment;
-}
-
 export default LatencyCompensator;

web/components/video/settings-menu.ts

@@ -1,32 +1,37 @@
-export default function createVideoSettingsMenuButton(player, videojs, qualities): any {
-  // const VjsMenuItem = videojs.getComponent('MenuItem');
+export default function createVideoSettingsMenuButton(
+  player,
+  videojs,
+  qualities,
+  latencyItemPressed,
+): any {
+  const VjsMenuItem = videojs.getComponent('MenuItem');
   const MenuItem = videojs.getComponent('MenuItem');
   const MenuButtonClass = videojs.getComponent('MenuButton');
 
-  // class MenuSeparator extends VjsMenuItem {
-  //   // eslint-disable-next-line no-useless-constructor
-  //   constructor(p: any, options: { selectable: boolean }) {
-  //     super(p, options);
-  //   }
-
-  //   createEl(tag = 'button', props = {}, attributes = {}) {
-  //     const el = super.createEl(tag, props, attributes);
-  //     el.innerHTML = '<hr style="opacity: 0.3; margin-left: 10px; margin-right: 10px;" />';
-  //     return el;
-  //   }
-  // }
+  class MenuSeparator extends VjsMenuItem {
+    // eslint-disable-next-line no-useless-constructor
+    constructor(p: any, options: { selectable: boolean }) {
+      super(p, options);
+    }
+
+    createEl(tag = 'button', props = {}, attributes = {}) {
+      const el = super.createEl(tag, props, attributes);
+      el.innerHTML = '<hr style="opacity: 0.3; margin-left: 10px; margin-right: 10px;" />';
+      return el;
+    }
+  }
 
   const lowLatencyItem = new MenuItem(player, {
     selectable: true,
   });
   lowLatencyItem.setAttribute('class', 'latency-toggle-item');
   lowLatencyItem.on('click', () => {
-    this.toggleLatencyCompensator();
+    latencyItemPressed();
   });
 
-  // const separator = new MenuSeparator(player, {
-  //   selectable: false,
-  // });
+  const separator = new MenuSeparator(player, {
+    selectable: false,
+  });
 
   const MenuButton = videojs.extend(MenuButtonClass, {
     // The `init()` method will also work for constructor logic here, but it is
@@ -75,16 +80,16 @@ export default function createVideoSettingsMenuButton(player, videojs, qualities
         defaultAutoItem.selected(false);
       });
 
-      const supportsLatencyCompensator = false; // !!tech && !!tech.vhs;
+      const supportsLatencyCompensator = !!tech && !!tech.vhs;
 
       // Only show the quality selector if there is more than one option.
-      // if (qualities.length < 2 && supportsLatencyCompensator) {
-      //   return [lowLatencyItem];
-      // }
+      if (qualities.length < 2 && supportsLatencyCompensator) {
+        return [lowLatencyItem];
+      }
 
-      // if (qualities.length > 1 && supportsLatencyCompensator) {
-      //   return [defaultAutoItem, ...items, separator, lowLatencyItem];
-      // }
+      if (qualities.length > 1 && supportsLatencyCompensator) {
+        return [defaultAutoItem, ...items, separator, lowLatencyItem];
+      }
       if (!supportsLatencyCompensator && qualities.length === 1) {
         return [];
       }