Add video duration handling for chat rendering and merging

modules/utils.py

@@ -98,6 +98,47 @@ def get_unique_filename(filepath: str) -> str:
         counter += 1
 
 
+def get_video_duration(video_path: str, ffmpeg_path: str) -> Optional[float]:
+    """
+    Get the duration of a video file in seconds using FFmpeg.
+    
+    Args:
+        video_path: Path to the video file
+        ffmpeg_path: Path to FFmpeg executable
+        
+    Returns:
+        float: Duration in seconds, or None if failed
+    """
+    if not os.path.exists(video_path):
+        return None
+    
+    try:
+        # Use ffprobe (comes with ffmpeg) to get duration
+        ffprobe_path = ffmpeg_path.replace('ffmpeg', 'ffprobe')
+        
+        cmd = [
+            ffprobe_path,
+            '-v', 'error',
+            '-show_entries', 'format=duration',
+            '-of', 'default=noprint_wrappers=1:nokey=1',
+            video_path
+        ]
+        
+        result = subprocess.run(
+            cmd,
+            capture_output=True,
+            text=True,
+            timeout=30
+        )
+        
+        if result.returncode == 0 and result.stdout.strip():
+            return float(result.stdout.strip())
+    except Exception:
+        pass
+    
+    return None
+
+
 def verify_streamlink() -> bool:
     """
     Verify that streamlink is available.