fix: cross-segment concat seeking + GUI time display after seeks

crates/reco-gui/src/main.rs

@@ -2801,7 +2801,9 @@ fn main() -> anyhow::Result<()> {
                 let img = s.render_current();
                 if let (Some(app), Some(img)) = (app_weak.upgrade(), img) {
                     app.set_preview_frame(img);
-                    app.set_current_frame(s.playback.frame_index() as i32);
+                    let fps = s.playback.fps();
+                    let total = s.playback.total_frames().unwrap_or(0);
+                    sync_frame_display(&app, s.playback.frame_index(), total, fps);
                 }
             }
             Ok(false) => {}
@@ -2831,7 +2833,9 @@ fn main() -> anyhow::Result<()> {
                 let img = s.render_current();
                 if let (Some(app), Some(img)) = (app_weak.upgrade(), img) {
                     app.set_preview_frame(img);
-                    app.set_current_frame(s.playback.frame_index() as i32);
+                    let fps = s.playback.fps();
+                    let total = s.playback.total_frames().unwrap_or(0);
+                    sync_frame_display(&app, s.playback.frame_index(), total, fps);
                 }
             }
             Err(e) => log::error!("Step backward error: {e}"),
@@ -2948,7 +2952,9 @@ fn main() -> anyhow::Result<()> {
         let img = s.render_current();
         if let (Some(app), Some(img)) = (app_weak.upgrade(), img) {
             app.set_preview_frame(img);
-            app.set_current_frame(s.playback.frame_index() as i32);
+            let fps = s.playback.fps();
+            let total = s.playback.total_frames().unwrap_or(0);
+            sync_frame_display(&app, s.playback.frame_index(), total, fps);
         }
     });
 
@@ -4179,7 +4185,9 @@ fn main() -> anyhow::Result<()> {
                         let img = s.render_current();
                         if let (Some(app), Some(img)) = (app_weak.upgrade(), img) {
                             app.set_preview_frame(img);
-                            app.set_current_frame(s.playback.frame_index() as i32);
+                            let fps = s.playback.fps();
+                            let total = s.playback.total_frames().unwrap_or(0);
+                            sync_frame_display(&app, s.playback.frame_index(), total, fps);
                             s.last_render_at = Some(Instant::now());
                         }
                     }

crates/reco-io/src/ffmpeg/decoder.rs

@@ -241,6 +241,40 @@ impl Drop for VideoDecoder {
     }
 }
 
+fn container_duration_secs(path: &Path) -> Result<Option<f64>, DecodeError> {
+    let ictx = input(path)?;
+    let duration = ictx.duration();
+    if duration > 0 {
+        Ok(Some(duration as f64 / f64::from(ffmpeg::ffi::AV_TIME_BASE)))
+    } else {
+        Ok(None)
+    }
+}
+
+fn concat_seek_durations(paths: &[std::path::PathBuf]) -> Option<Vec<f64>> {
+    let mut durations = Vec::with_capacity(paths.len());
+    for path in paths {
+        match container_duration_secs(path) {
+            Ok(Some(duration)) => durations.push(duration),
+            Ok(None) => {
+                log::warn!(
+                    "Concat demuxer: duration unknown for {}; cross-segment seek may be unavailable",
+                    path.display()
+                );
+                return None;
+            }
+            Err(e) => {
+                log::warn!(
+                    "Concat demuxer: failed to probe duration for {} ({e}); cross-segment seek may be unavailable",
+                    path.display()
+                );
+                return None;
+            }
+        }
+    }
+    Some(durations)
+}
+
 impl VideoDecoder {
     /// Open a video file for decoding.
     ///
@@ -509,12 +543,17 @@ impl VideoDecoder {
             .suffix(".txt")
             .tempfile()
             .map_err(|e| DecodeError::Ffmpeg(format!("concat manifest: {e}")))?;
+        let durations = concat_seek_durations(paths);
 
         writeln!(manifest, "ffconcat version 1.0")
             .map_err(|e| DecodeError::Ffmpeg(format!("write manifest: {e}")))?;
-        for p in paths {
+        for (idx, p) in paths.iter().enumerate() {
             writeln!(manifest, "file '{}'", p.display())
                 .map_err(|e| DecodeError::Ffmpeg(format!("write manifest: {e}")))?;
+            if let Some(durations) = durations.as_ref() {
+                writeln!(manifest, "duration {:.6}", durations[idx])
+                    .map_err(|e| DecodeError::Ffmpeg(format!("write manifest: {e}")))?;
+            }
         }
         manifest
             .flush()