Fix multi-shot chain preview inSec for scenes 2+.

Preview now uses the same render.inSec + source_in mapping as export for
every scene in a shared chain file, including converted video clips.

movie_editor/frontend/player.js

@@ -182,14 +182,14 @@
           sceneId: sc.id,
           startSec,
           durationSec: clipDur,
-          inSec: sc.source_in || 0,
+          inSec: S.clipSourceInSec ? S.clipSourceInSec(sc, r) : (sc.source_in || 0),
           fx,
           vol,
         });
         continue;
       }
 
-      const inSec = (sc.source_in || 0) + (r?.inSec || 0);
+      const inSec = S.clipSourceInSec ? S.clipSourceInSec(sc, r) : ((sc.source_in || 0) + (r?.inSec || 0));
       if (r && r.media) {
         out.push({
           media: r.media, sceneId: sc.id, startSec, durationSec: dur, inSec,
@@ -567,14 +567,18 @@
       return;
     }
     const offset = _phSec - clip.startSec;
-    const sameClip = _currentClip === clip
-      || (_currentClip && clip && _currentClip.sceneId === clip.sceneId && _sameVideoUrl(_currentClip, clip));
-    const sameVideo = !clip.pending && _active && _sameVideoUrl(_currentClip, clip)
+    const prevClip = _currentClip;
+    const sameClip = prevClip === clip
+      || (prevClip && clip && prevClip.sceneId === clip.sceneId && _sameVideoUrl(prevClip, clip));
+    const sameVideo = !clip.pending && _active && _sameVideoUrl(prevClip || clip, clip)
       && (clip.media || clip.binUrl);
     if (sameVideo && _active.readyState >= 1) {
+      const crossScene = prevClip && clip && prevClip !== clip
+        && (prevClip.sceneId !== clip.sceneId || Math.abs((prevClip.inSec || 0) - (clip.inSec || 0)) > 0.05);
       _currentClip = clip;
       _applyClipUi(clip);
       const target = (clip.inSec || 0) + Math.max(0, offset);
+      if (crossScene) _flushVideoSeek(true);
       _scheduleVideoSeek(target, clip, offset);
     } else if (!sameClip || clip.pending) {
       _flushVideoSeek(true);

movie_editor/frontend/store.js

@@ -1492,7 +1492,7 @@
     if (separatedTrackForScene(sceneId)) return;
     _historyRecord();
     const idx = state.project.scenes.indexOf(sc);
-    const inSec = (r.inSec || 0) + (sc.source_in || 0);
+    const inSec = clipSourceInSec(sc, r);
     const dur = sc.source_dur != null ? sc.source_dur : sceneDurationSec(sc);
     const savedVol = sc.audio_volume != null ? sc.audio_volume : 1;
     state.project.audio_tracks = state.project.audio_tracks || [];
@@ -2312,6 +2312,14 @@
     await _saveBlobAs(API.mediaUrl(mediaId), name, { types });
   }
 
+  // Source in-point for preview/export: chain segment offset + per-scene trim.
+  function clipSourceInSec(sc, render) {
+    if (!sc) return 0;
+    const trim = sc.source_in || 0;
+    if (render?.media) return trim + (render.inSec || 0);
+    return trim;
+  }
+
   // Ordered list of rendered clips in timeline order: {media, inSec, durationSec} for
   // each non-excluded scene that has a render. This is what plays/exports — so splits
   // and deletes are honoured (deleted scenes simply aren't here).
@@ -2324,7 +2332,7 @@
       const fps = (sc.fps_mode !== "project" && sc.fps != null ? sc.fps : p.frame_rate) || 25;
       const tFrames = sc.transition_frames || 0;
       const base = {
-        inSec: (r?.inSec || 0) + (sc.source_in || 0),
+        inSec: clipSourceInSec(sc, r),
         durationSec: sc.source_dur != null ? sc.source_dur : sceneDurationSec(sc),
         fx: sc.effects || {}, fps,
         w: (sc.width != null ? sc.width : p.width) || null,
@@ -2431,7 +2439,7 @@
         filename: r.media.filename,
         subfolder: r.media.subfolder || "",
         type: r.media.type || "output",
-        in: (r.inSec || 0) + (sc.source_in || 0),
+        in: clipSourceInSec(sc, r),
         dur: sc.source_dur != null ? sc.source_dur : sceneDurationSec(sc),
       },
       name: `${proj}_scene${idx >= 0 ? idx + 1 : "x"}_${_stamp()}.mp4`,
@@ -2866,7 +2874,7 @@
     sceneCharacterIds, toggleSceneCharacter,
     genUnitId, isGenSubclip, genUnitRoot, genUnitSceneIds,
     renderPromptForScene, renderPromptMismatch, renderAnchorMismatch, renderMediaLabel, renderIsStale,
-    buildPreviewSegments, previewTotalSec, segmentDurationSec, sceneDurationSec,
+    buildPreviewSegments, previewTotalSec, segmentDurationSec, sceneDurationSec, clipSourceInSec,
     addAudioTrack, updateAudioTrack, removeAudioTrack, separateSceneAudio, separatedTrackForScene,
     separatedTrackMedia, separatedTrackInSec, separatedTrackDurSec,
     isOverlayAudioTrack, isSeparatedAudioTrack,

movie_editor/frontend/view_bus.js

@@ -81,6 +81,7 @@
       scenes: (p.scenes || []).map((s) => [
         s.id, s.excluded, s.frames, s.fps, s.frames_mode, s.fps_mode,
         s.audio_volume, s.audio_separated, s.source_in, s.source_dur, s.effects,
+        s.source?.type, s.source?.media_ref,
       ]),
       renders: st.sceneRenders,
       ghosts: st.sceneGhosts,