Fix the bug that multi webcam detection failed with OpenVINO

It would failed with the following error when detect multi webcam.
"Input blob size is not equal network input size (2457600!=1228800)"

Signed-off-by: Chao Qin <chaoqin_cmkj@163.com>

detect.py

@@ -122,12 +122,23 @@ def run(
             im /= 255  # 0 - 255 to 0.0 - 1.0
             if len(im.shape) == 3:
                 im = im[None]  # expand for batch dim
+            if model.xml and im.shape[0] > 1:
+                ims = torch.chunk(im, im.shape[0], 0)
 
         # Inference
         with dt[1]:
             visualize = increment_path(save_dir / Path(path).stem, mkdir=True) if visualize else False
-            pred = model(im, augment=augment, visualize=visualize)
-
+            if model.xml and im.shape[0] > 1:
+                pred = None
+                for image in ims:
+                    if pred is None:
+                        pred = model(image, augment=augment, visualize=visualize).unsqueeze(0)
+                    else:
+                        pred = torch.cat((pred, model(
+                            image, augment=augment, visualize=visualize).unsqueeze(0)), dim=0)
+                pred = [pred, None]
+            else:
+                pred = model(im, augment=augment, visualize=visualize)
         # NMS
         with dt[2]:
             pred = non_max_suppression(pred, conf_thres, iou_thres, classes, agnostic_nms, max_det=max_det)