Inference API support video (#995)

* Inference API support video

* Using mmcv.VideoReader to read video

* modify

GETTING_STARTED.md

@@ -63,6 +63,7 @@ Here is an example of building the model and test given images.
 
 ```python
 from mmdet.apis import init_detector, inference_detector, show_result
+import mmcv
 
 config_file = 'configs/faster_rcnn_r50_fpn_1x.py'
 checkpoint_file = 'checkpoints/faster_rcnn_r50_fpn_1x_20181010-3d1b3351.pth'
@@ -79,6 +80,12 @@ show_result(img, result, model.CLASSES)
 imgs = ['test1.jpg', 'test2.jpg']
 for i, result in enumerate(inference_detector(model, imgs)):
     show_result(imgs[i], result, model.CLASSES, out_file='result_{}.jpg'.format(i))
+
+# test a video and show the results
+video = mmcv.VideoReader('video.mp4')
+for frame in video:
+    result = inference_detector(model, frame)
+    show_result(frame, result, model.CLASSES, wait_time=1)
 ```
 
 

mmdet/apis/inference.py

@@ -100,7 +100,12 @@ def _inference_generator(model, imgs, img_transform, device):
 
 
 # TODO: merge this method with the one in BaseDetector
-def show_result(img, result, class_names, score_thr=0.3, out_file=None):
+def show_result(img,
+                result,
+                class_names,
+                score_thr=0.3,
+                wait_time=0,
+                out_file=None):
     """Visualize the detection results on the image.
 
     Args:
@@ -109,6 +114,7 @@ def show_result(img, result, class_names, score_thr=0.3, out_file=None):
             (bbox, segm) or just bbox.
         class_names (list[str] or tuple[str]): A list of class names.
         score_thr (float): The threshold to visualize the bboxes and masks.
+        wait_time (int): Value of waitKey param.
         out_file (str, optional): If specified, the visualization result will
             be written to the out file instead of shown in a window.
     """
@@ -140,4 +146,5 @@ def show_result(img, result, class_names, score_thr=0.3, out_file=None):
         class_names=class_names,
         score_thr=score_thr,
         show=out_file is None,
+        wait_time=wait_time,
         out_file=out_file)