Improve HLS handling for startPosition

The startPosition was incorrectly calculated assuming continuous recordings, when it needs to consider only some segments exist. This extracts that logic to a utility so all can use it.

web/src/components/player/dynamic/DynamicVideoController.ts

@@ -2,7 +2,10 @@ import { Recording } from "@/types/record";
 import { DynamicPlayback } from "@/types/playback";
 import { PreviewController } from "../PreviewPlayer";
 import { TimeRange, TrackingDetailsSequence } from "@/types/timeline";
-import { calculateInpointOffset } from "@/utils/videoUtil";
+import {
+  calculateInpointOffset,
+  calculateSeekPosition,
+} from "@/utils/videoUtil";
 
 type PlayerMode = "playback" | "scrubbing";
 
@@ -72,39 +75,21 @@ export class DynamicVideoController {
       return;
     }
 
-    if (
-      this.recordings.length == 0 ||
-      time < this.recordings[0].start_time ||
-      time > this.recordings[this.recordings.length - 1].end_time
-    ) {
-      this.setNoRecording(true);
-      return;
-    }
-
     if (this.playerMode != "playback") {
       this.playerMode = "playback";
     }
 
-    let seekSeconds = 0;
-    (this.recordings || []).every((segment) => {
-      // if the next segment is past the desired time, stop calculating
-      if (segment.start_time > time) {
-        return false;
+    const seekSeconds = calculateSeekPosition(
+      time,
+      this.recordings,
+      this.inpointOffset,
+    );
+
+    if (seekSeconds === undefined) {
+      this.setNoRecording(true);
+      return;
     }
 
-      if (segment.end_time < time) {
-        seekSeconds += segment.end_time - segment.start_time;
-        return true;
-      }
-
-      seekSeconds +=
-        segment.end_time - segment.start_time - (segment.end_time - time);
-      return true;
-    });
-
-    // adjust for HLS inpoint offset
-    seekSeconds -= this.inpointOffset;
-
     if (seekSeconds != 0) {
       this.playerController.currentTime = seekSeconds;
 

web/src/components/player/dynamic/DynamicVideoPlayer.tsx

@@ -14,7 +14,10 @@ import { VideoResolutionType } from "@/types/live";
 import axios from "axios";
 import { cn } from "@/lib/utils";
 import { useTranslation } from "react-i18next";
-import { calculateInpointOffset } from "@/utils/videoUtil";
+import {
+  calculateInpointOffset,
+  calculateSeekPosition,
+} from "@/utils/videoUtil";
 import { isFirefox } from "react-device-detect";
 
 /**
@@ -109,10 +112,10 @@ export default function DynamicVideoPlayer({
   const [isLoading, setIsLoading] = useState(false);
   const [isBuffering, setIsBuffering] = useState(false);
   const [loadingTimeout, setLoadingTimeout] = useState<NodeJS.Timeout>();
-  const [source, setSource] = useState<HlsSource>({
-    playlist: `${apiHost}vod/${camera}/start/${timeRange.after}/end/${timeRange.before}/master.m3u8`,
-    startPosition: startTimestamp ? startTimestamp - timeRange.after : 0,
-  });
+
+  // Don't set source until recordings load - we need accurate startPosition
+  // to avoid hls.js clamping to video end when startPosition exceeds duration
+  const [source, setSource] = useState<HlsSource | undefined>(undefined);
 
   // start at correct time
 
@@ -184,7 +187,7 @@ export default function DynamicVideoPlayer({
   );
 
   useEffect(() => {
-    if (!controller || !recordings?.length) {
+    if (!recordings?.length) {
       if (recordings?.length == 0) {
         setNoRecording(true);
       }
@@ -192,10 +195,6 @@ export default function DynamicVideoPlayer({
       return;
     }
 
-    if (playerRef.current) {
-      playerRef.current.autoplay = !isScrubbing;
-    }
-
     let startPosition = undefined;
 
     if (startTimestamp) {
@@ -203,14 +202,12 @@ export default function DynamicVideoPlayer({
         recordingParams.after,
         (recordings || [])[0],
       );
-      const idealStartPosition = Math.max(
-        0,
-        startTimestamp - timeRange.after - inpointOffset,
-      );
 
-      if (idealStartPosition >= recordings[0].start_time - timeRange.after) {
-        startPosition = idealStartPosition;
-      }
+      startPosition = calculateSeekPosition(
+        startTimestamp,
+        recordings,
+        inpointOffset,
+      );
     }
 
     setSource({
@@ -218,6 +215,18 @@ export default function DynamicVideoPlayer({
       startPosition,
     });
 
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [recordings]);
+
+  useEffect(() => {
+    if (!controller || !recordings?.length) {
+      return;
+    }
+
+    if (playerRef.current) {
+      playerRef.current.autoplay = !isScrubbing;
+    }
+
     setLoadingTimeout(setTimeout(() => setIsLoading(true), 1000));
 
     controller.newPlayback({
@@ -225,7 +234,7 @@ export default function DynamicVideoPlayer({
       timeRange,
     });
 
-    // we only want this to change when recordings update
+    // we only want this to change when controller or recordings update
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [controller, recordings]);
 
@@ -263,6 +272,7 @@ export default function DynamicVideoPlayer({
 
   return (
     <>
+      {source && (
         <HlsVideoPlayer
           videoRef={playerRef}
           containerRef={containerRef}
@@ -303,6 +313,7 @@ export default function DynamicVideoPlayer({
           camera={contextCamera || camera}
           currentTimeOverride={currentTime}
         />
+      )}
       <PreviewPlayer
         className={cn(
           className,

web/src/utils/videoUtil.ts

@@ -24,3 +24,57 @@ export function calculateInpointOffset(
 
   return 0;
 }
+
+/**
+ * Calculates the video player time (in seconds) for a given timestamp
+ * by iterating through recording segments and summing their durations.
+ * This accounts for the fact that the video is a concatenation of segments,
+ * not a single continuous stream.
+ *
+ * @param timestamp - The target timestamp to seek to
+ * @param recordings - Array of recording segments
+ * @param inpointOffset - HLS inpoint offset to subtract from the result
+ * @returns The calculated seek position in seconds, or undefined if timestamp is out of range
+ */
+export function calculateSeekPosition(
+  timestamp: number,
+  recordings: Recording[],
+  inpointOffset: number = 0,
+): number | undefined {
+  if (!recordings || recordings.length === 0) {
+    return undefined;
+  }
+
+  // Check if timestamp is within the recordings range
+  if (
+    timestamp < recordings[0].start_time ||
+    timestamp > recordings[recordings.length - 1].end_time
+  ) {
+    return undefined;
+  }
+
+  let seekSeconds = 0;
+
+  (recordings || []).every((segment) => {
+    // if the next segment is past the desired time, stop calculating
+    if (segment.start_time > timestamp) {
+      return false;
+    }
+
+    if (segment.end_time < timestamp) {
+      // Add the full duration of this segment
+      seekSeconds += segment.end_time - segment.start_time;
+      return true;
+    }
+
+    // We're in this segment - calculate position within it
+    seekSeconds +=
+      segment.end_time - segment.start_time - (segment.end_time - timestamp);
+    return true;
+  });
+
+  // Adjust for HLS inpoint offset
+  seekSeconds -= inpointOffset;
+
+  return seekSeconds >= 0 ? seekSeconds : undefined;
+}