* [maixcam2] optimize doc

Author: lxowalle

docs/doc/en/video/play.md

@@ -39,6 +39,7 @@ while not app.need_exit():
     img = ctx.image()
     disp.show(img)
     print(f'need wait : {ctx.duration_us()} us')
+    time.sleep_us(ctx.duration_us())
 ```
 
 Steps:

docs/doc/zh/video/play.md

@@ -25,7 +25,7 @@ ffmpeg -i input_video.mp4 -c:v libx264 -x264opts "bframes=0" -c:a aac -strict ex
 一个播放`mp4`视频的示例，视频文件路径为`/root/output.mp4`
 
 ```python
-from maix import video, display, app
+from maix import video, display, app, time
 
 disp = display.Display()
 d = video.Decoder('/root/output.mp4')
@@ -40,6 +40,7 @@ while not app.need_exit():
     img = ctx.image()
     disp.show(img)
     print(f'need wait : {ctx.duration_us()} us')
+    time.sleep_us(ctx.duration_us())
 ```
 
 步骤：

projects/app_vlm/main.py

@@ -266,5 +266,4 @@ def run(self):
 
 if __name__ == '__main__':
     appication = App()
-    appication.run()
-    print('===========')
+    appication.run()