fix bug on safari where a live stream will play at the time=0 rather than next to the live edge when using startAt:fromLastPosition

Author: Florent-Bouisset

src/main_thread/init/directfile_content_initializer.ts

@@ -254,7 +254,7 @@ export default class DirectFileContentInitializer extends ContentInitializer {
 function getDirectFileInitialTime(
   mediaElement: IMediaElement,
   startAt?: IInitialTimeOptions,
-): number {
+): number | undefined {
   if (isNullOrUndefined(startAt)) {
     return 0;
   }
@@ -268,28 +268,38 @@ function getDirectFileInitialTime(
   }
 
   const duration = mediaElement.duration;
-
   if (typeof startAt.fromLastPosition === "number") {
-    if (isNullOrUndefined(duration) || !isFinite(duration)) {
-      log.warn(
-        "startAt.fromLastPosition set but no known duration, " + "beginning at 0.",
-      );
-      return 0;
+    if (!isNullOrUndefined(duration) && isFinite(duration)) {
+      return Math.max(0, duration + startAt.fromLastPosition);
     }
-    return Math.max(0, duration + startAt.fromLastPosition);
+
+    if (mediaElement.seekable.length > 0) {
+      const lastSegmentEnd = mediaElement.seekable.end(mediaElement.seekable.length - 1);
+      if (isFinite(lastSegmentEnd)) {
+        return Math.max(0, lastSegmentEnd + startAt.fromLastPosition);
+      }
+    }
+    log.warn(
+      "Init: startAt.fromLastPosition set but no known duration, " +
+        "it may be too soon to seek",
+    );
+    return undefined;
   } else if (typeof startAt.fromLivePosition === "number") {
     const livePosition =
       mediaElement.seekable.length > 0 ? mediaElement.seekable.end(0) : duration;
     if (isNullOrUndefined(livePosition)) {
       log.warn(
-        "startAt.fromLivePosition set but no known live position, " + "beginning at 0.",
+        "Init: startAt.fromLivePosition set but no known live position, " +
+          "beginning at 0.",
       );
       return 0;
     }
     return Math.max(0, livePosition + startAt.fromLivePosition);
   } else if (!isNullOrUndefined(startAt.percentage)) {
     if (isNullOrUndefined(duration) || !isFinite(duration)) {
-      log.warn("startAt.percentage set but no known duration, " + "beginning at 0.");
+      log.warn(
+        "Init: startAt.percentage set but no known duration, " + "beginning at 0.",
+      );
       return 0;
     }
     const { percentage } = startAt;

src/main_thread/init/utils/initial_seek_and_play.ts

@@ -71,7 +71,7 @@ export default function performInitialSeekAndPlay(
   }: {
     mediaElement: IMediaElement;
     playbackObserver: IMediaElementPlaybackObserver;
-    startTime: number | (() => number);
+    startTime: number | (() => number | undefined);
     mustAutoPlay: boolean;
     isDirectfile: boolean;
     onWarning: (err: IPlayerError) => void;
@@ -107,18 +107,37 @@ export default function performInitialSeekAndPlay(
       if (!isDirectfile || typeof startTime === "number") {
         const initiallySeekedTime =
           typeof startTime === "number" ? startTime : startTime();
-        if (initiallySeekedTime !== 0) {
+        if (initiallySeekedTime !== 0 && initiallySeekedTime !== undefined) {
           performInitialSeek(initiallySeekedTime);
         }
         waitForSeekable();
       } else {
         playbackObserver.listen(
           (obs, stopListening) => {
+            const initiallySeekedTime =
+              typeof startTime === "number" ? startTime : startTime();
+            if (
+              initiallySeekedTime === undefined &&
+              obs.readyState < HTMLMediaElement.HAVE_CURRENT_DATA
+            ) {
+              /**
+               * On browser, such as Safari, the HTMLMediaElement.duration
+               * and HTMLMediaElement.buffered may not be initialized at readyState 1, leading
+               * to cases where it can be equal to `Infinity`.
+               * If so, the range in which it is possible to seek is not yet known.
+               * To solve this, the seek should be done after readyState HAVE_CURRENT_DATA (2),
+               * at that time the previously mentioned attributes are correctly initialized and
+               * the range in which it is possible to seek is correctly known.
+               * If the initiallySeekedTime is still `undefined` when the readyState is >= 2,
+               * let assume that the initiallySeekedTime will never be known and continue
+               * the logic without seeking.
+               */
+              return;
+            }
             if (obs.readyState >= 1) {
               stopListening();
-              const initiallySeekedTime =
-                typeof startTime === "number" ? startTime : startTime();
-              if (initiallySeekedTime !== 0) {
+
+              if (initiallySeekedTime !== 0 && initiallySeekedTime !== undefined) {
                 if (canSeekDirectlyAfterLoadedMetadata) {
                   performInitialSeek(initiallySeekedTime);
                 } else {