teleop sync: hold master back for stuck-behind tiles (no more start-replay on slow bandwidth)

teleopSample/sort_ep0.html

@@ -129,25 +129,23 @@ function activeSpan(t){ for(let i=0;i<SPANS.length;i++) if(t>=SPANS[i].start_s&&
 let playing=false, raf=0, syncTimer=0, _lastCi=-2;
 function inBuf(v,t){ const b=v.buffered; for(let i=0;i<b.length;i++) if(t>=b.start(i)-0.2&&t<=b.end(i)+0.2) return true; return false; }
 function syncSlaves(t,hard){
-  for(const v of vids){ if(v===master||v.readyState<1) continue;
-    if(hard){ v.playbackRate=1; if(!v.seeking&&Math.abs(v.currentTime-t)>0.06){ try{v.currentTime=t;}catch(e){} } continue; }
-    if(!playing) continue;
+  if(hard){
+    for(const v of vids){ if(v.readyState<1) continue; v.playbackRate=1;
+      if(v!==master && !v.seeking && Math.abs(v.currentTime-t)>0.06){ try{v.currentTime=t;}catch(e){} } }
+    return;
+  }
+  let worstLag = 0;
+  for(const v of vids){ if(v===master||v.readyState<1||!playing) continue;
     if(v.paused&&!v.ended){ v.play().catch(()=>{}); }
-    const drift=v.currentTime-t, ad=Math.abs(drift);   // drift<0 => this tile is behind
-    if(ad>1.0 && !v.seeking){
-      // big gap: jump to master if it's downloaded here, otherwise to the freshest
-      // buffered point of THIS tile — so a slow-loading tile skips ahead to current
-      // content instead of crawling from the start (which looked like a replay loop)
-      let tgt = inBuf(v,t) ? t
-        : (v.buffered.length ? Math.max(0, v.buffered.end(v.buffered.length-1)-0.25) : v.currentTime);
-      if(Math.abs(v.currentTime-tgt)>0.4){ try{ v.currentTime=tgt; }catch(e){} }
-      v.playbackRate=1;
-    } else if(ad>0.04){
-      v.playbackRate=Math.max(0.5,Math.min(1.8, 1-drift*3));   // trim toward master
-    } else {
-      v.playbackRate=1;
-    }
+    const drift=v.currentTime-t, ad=Math.abs(drift);      // drift<0 => this tile is behind
+    if(drift < -0.3) worstLag = Math.max(worstLag, -drift);
+    if(ad>1.0 && !v.seeking && inBuf(v,t)){ try{v.currentTime=t;}catch(e){} v.playbackRate=1; }
+    else if(ad>0.04){ v.playbackRate=Math.max(0.5,Math.min(1.8, 1-drift*3)); }
+    else v.playbackRate=1;
   }
+  // a tile stuck far behind can't be seeked forward (still downloading) — hold the
+  // master back so all views stay together instead of the laggards looping the start
+  if(master && playing) master.playbackRate = worstLag>1.5 ? 0.25 : (worstLag>0.6 ? 0.6 : 1);
 }
 function seekTo(t){ t=Math.max(0,Math.min(DUR-0.01,t));
   try{ if(Math.abs(master.currentTime-t)>0.05) master.currentTime=t; }catch(e){}