CameraBase: keep the newest frames when the camera kept several

src/pymodaq_plugins_utils/hardware/camera_base.py

@@ -107,17 +107,17 @@ def wait_for_acquisition(self, mode: Grab):
                                 return
                             continue
 
-                        # in case hardware has a random buffer size (ex: Andor CCD cameras)
-                        if new_frames.shape[0] != mode.nframes:
-                            new_frames = np.expand_dims(new_frames[-mode.nframes:], axis=0)
+                        # the camera may have kept more frames than the ones still missing (ex: nobody read while it
+                        # was acquiring, or Andor CCD cameras with a random buffer size): keep the newest ones
+                        n_missing = mode.nframes - ind_frames
+                        new_frames = new_frames[-n_missing:]
+                        n_new = new_frames.shape[0]
 
                         if ind_average == 0 and ind_frames == 0:
-                            shape = list(new_frames.shape[1:])
-                            shape = [mode.n_average, mode.nframes] + shape
+                            shape = [mode.n_average, mode.nframes] + list(new_frames.shape[1:])
                             frames = np.zeros(shape, dtype=new_frames.dtype)
-                        nacq = rng[1] - rng[0]
-                        frames[ind_average, ind_frames:nacq, ...] = new_frames
-                        ind_frames += nacq
+                        frames[ind_average, ind_frames:ind_frames + n_new, ...] = new_frames
+                        ind_frames += n_new
                     ind_average += 1
                 self.data_sig.emit(frames)
                 QtCore.QThread.msleep(10)

tests/test_camera_base.py

@@ -93,13 +93,26 @@ def get_pixel_size(self):
         return 5.0, 10.0
 
 
+class FakeCameraSeveralFrames(FakeCamera):
+    """A camera that kept several frames since the last read (as when nobody reads while it acquires)"""
+    n_unread = 3
+
+    def read_multiple_images(self, rng=None, peek=False, missing_frame='skip', return_rng=False):
+        frames = np.repeat(self.read_newest_image()[None, ...], self.n_unread, axis=0)
+        return (frames, (0, self.n_unread)) if return_rng else frames
+
+
 class DAQ_2DViewer_Fake(CameraBase):
     driver_class = FakeCamera
 
     def ini_detector_custom(self, controller=None):
         self.controller = self.driver_class() if self.is_master else controller
 
 
+class DAQ_2DViewer_FakeSeveralFrames(DAQ_2DViewer_Fake):
+    driver_class = FakeCameraSeveralFrames
+
+
 class DAQ_2DViewer_FakeWithPixelSize(DAQ_2DViewer_Fake):
     driver_class = FakeCameraWithPixelSize
 
@@ -143,6 +156,17 @@ def set_binning(plugin, xbin: int, ybin: int):
         plugin.commit_settings(param)
 
 
+class TestSeveralUnreadFrames:
+    def test_a_snap_gives_one_image_when_the_camera_kept_several_frames(self, qapp):
+        plugin = make_detector(DAQ_2DViewer_FakeSeveralFrames)
+        try:
+            dte = grab_and_wait(plugin)
+            assert dte[0].dim.name == 'Data2D'
+            assert dte[0].shape == (HEIGHT, WIDTH)
+        finally:
+            plugin.close()
+
+
 class TestDriverContract:
     @pytest.mark.parametrize('method, args', [
         ('get_detector_size', ()), ('get_data_dimensions', ()), ('get_roi', ()), ('set_roi', ()),