[Feature] Support video demo (#1014)

* First commit for video demo

* fix lint

* update

* fix

* add wget in shell

demo/video_demo.py

@@ -0,0 +1,111 @@
+from argparse import ArgumentParser
+
+import cv2
+
+from mmseg.apis import inference_segmentor, init_segmentor
+from mmseg.core.evaluation import get_palette
+
+
+def main():
+    parser = ArgumentParser()
+    parser.add_argument('video', help='Video file or webcam id')
+    parser.add_argument('config', help='Config file')
+    parser.add_argument('checkpoint', help='Checkpoint file')
+    parser.add_argument(
+        '--device', default='cuda:0', help='Device used for inference')
+    parser.add_argument(
+        '--palette',
+        default='cityscapes',
+        help='Color palette used for segmentation map')
+    parser.add_argument(
+        '--show', action='store_true', help='Whether to show draw result')
+    parser.add_argument(
+        '--show-wait-time', default=1, type=int, help='Wait time after imshow')
+    parser.add_argument(
+        '--output-file', default=None, type=str, help='Output video file path')
+    parser.add_argument(
+        '--output-fourcc',
+        default='MJPG',
+        type=str,
+        help='Fourcc of the output video')
+    parser.add_argument(
+        '--output-fps', default=-1, type=int, help='FPS of the output video')
+    parser.add_argument(
+        '--output-height',
+        default=-1,
+        type=int,
+        help='Frame height of the output video')
+    parser.add_argument(
+        '--output-width',
+        default=-1,
+        type=int,
+        help='Frame width of the output video')
+    parser.add_argument(
+        '--opacity',
+        type=float,
+        default=0.5,
+        help='Opacity of painted segmentation map. In (0, 1] range.')
+    args = parser.parse_args()
+
+    assert args.show or args.output_file, \
+        'At least one output should be enabled.'
+
+    # build the model from a config file and a checkpoint file
+    model = init_segmentor(args.config, args.checkpoint, device=args.device)
+
+    # build input video
+    cap = cv2.VideoCapture(args.video)
+    assert (cap.isOpened())
+    input_height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
+    input_width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
+    input_fps = cap.get(cv2.CAP_PROP_FPS)
+
+    # init output video
+    writer = None
+    output_height = None
+    output_width = None
+    if args.output_file is not None:
+        fourcc = cv2.VideoWriter_fourcc(*args.output_fourcc)
+        output_fps = args.output_fps if args.output_fps > 0 else input_fps
+        output_height = args.output_height if args.output_height > 0 else int(
+            input_height)
+        output_width = args.output_width if args.output_width > 0 else int(
+            input_width)
+        writer = cv2.VideoWriter(args.output_file, fourcc, output_fps,
+                                 (output_width, output_height), True)
+
+    # start looping
+    try:
+        while True:
+            flag, frame = cap.read()
+            if not flag:
+                break
+
+            # test a single image
+            result = inference_segmentor(model, frame)
+
+            # blend raw image and prediction
+            draw_img = model.show_result(
+                frame,
+                result,
+                palette=get_palette(args.palette),
+                show=False,
+                opacity=args.opacity)
+
+            if args.show:
+                cv2.imshow('video_demo', draw_img)
+                cv2.waitKey(args.show_wait_time)
+            if writer:
+                if draw_img.shape[0] != output_height or draw_img.shape[
+                        1] != output_width:
+                    draw_img = cv2.resize(draw_img,
+                                          (output_width, output_height))
+                writer.write(draw_img)
+    finally:
+        if writer:
+            writer.release()
+        cap.release()
+
+
+if __name__ == '__main__':
+    main()

docs/get_started.md

@@ -216,3 +216,21 @@ python demo/image_demo.py demo/demo.jpg configs/pspnet/pspnet_r50-d8_512x1024_40
 ```
 
 A notebook demo can be found in [demo/inference_demo.ipynb](../demo/inference_demo.ipynb).
+
+Now we also provide a demo script to test a single video.
+
+```shell
+wget -O demo/demo.mp4 https://user-images.githubusercontent.com/22089207/144212749-44411ef4-b564-4b37-96d4-04bedec629ab.mp4
+python demo/video_demo.py ${VIDEO_FILE} ${CONFIG_FILE} ${CHECKPOINT_FILE} [--device ${DEVICE_NAME}] [--palette-thr ${PALETTE}] \
+    [--show] [--show-wait-time {SHOW_WAIT_TIME}] [--output-file {OUTPUT_FILE}] [--output-fps {OUTPUT_FPS}] \
+    [--output-height {OUTPUT_HEIGHT}] [--output-width {OUTPUT_WIDTH}] [--opacity {OPACITY}]
+```
+
+Examples:
+
+```shell
+wget -O demo/demo.mp4 https://user-images.githubusercontent.com/22089207/144212749-44411ef4-b564-4b37-96d4-04bedec629ab.mp4
+python demo/video_demo.py demo/demo.mp4 configs/cgnet/cgnet_680x680_60k_cityscapes.py \
+    checkpoints/cgnet_680x680_60k_cityscapes_20201101_110253-4c0b2f2d.pth \
+    --device cuda:0 --palette cityscapes --show
+```