Refine vnc recording

Some experimentation shows that 15 fps is more than enough for the vast majority of console activity, so cut back for reduced file size.

Also, the calculation for last frame was incorrect, tracking duration based on when exiting caught up to the queue.  Now add the end time explicitly and use that to reduce last frame lingering.

VP9 is still uncomfortably slow in a default setup, so stick with MP4V despite larger size, user may transcode if they want to make it smaller.

confluent_client/confluent/vnc.py

@@ -51,7 +51,7 @@ class VNCClient:
         return False
     
     @classmethod
-    async def create(cls, url, outputfile=None, fps=30):
+    async def create(cls, url, outputfile=None, fps=15):
         self = cls()
         self.outputfile = outputfile
         self.fps = fps
@@ -249,19 +249,18 @@ class VNCClient:
     def _video_worker(self):
         cv2 = self._cv2
         while True:
-            item = self._video_queue.get()
-            if item is None:
+            frame, now = self._video_queue.get()
+            if frame is None:
                 # Flush the final frame for the time it stayed on screen
                 if self.video_writer is not None and self._last_frame is not None:
                     nframes = max(1, round(
-                        (time.monotonic() - self._last_frame_time) * self.fps))
+                        (now - self._last_frame_time) * self.fps))
                     for _ in range(nframes):
                         self.video_writer.write(self._last_frame)
                 if self.video_writer is not None:
                     self.video_writer.release()
                     self.video_writer = None
                 return
-            frame, now = item
             if self.video_writer is None:
                 self._video_size = (frame.shape[1], frame.shape[0])
                 fourcc = cv2.VideoWriter_fourcc(*'mp4v')
@@ -340,7 +339,7 @@ class VNCClient:
     async def close(self):
         if self._video_thread is not None:
             # Signal the writer thread to flush and finalize the file
-            self._video_queue.put(None)
+            self._video_queue.put((None, time.monotonic()))
             await asyncio.to_thread(self._video_thread.join)
             self._video_thread = None
         self.writer.close()