Webcam: prepare to make camerad a PythonProcess (#31202)

* webcam

* support /dev/* syntax

* support strings

tools/webcam/camera.py

@@ -3,6 +3,10 @@ import numpy as np
 
 class Camera:
   def __init__(self, cam_type_state, stream_type, camera_id):
+    try:
+      camera_id = int(camera_id)
+    except ValueError: # allow strings, ex: /dev/video0
+      pass
     self.cam_type_state = cam_type_state
     self.stream_type = stream_type
     self.cur_frame_id = 0

tools/webcam/camerad.py

@@ -25,7 +25,7 @@ class Camerad:
 
     self.cameras = []
     for c in CAMERAS:
-      cam = Camera(c.msg_name, c.stream_type, int(c.cam_id))
+      cam = Camera(c.msg_name, c.stream_type, c.cam_id)
       assert cam.cap.isOpened(), f"Can't find camera {c}"
       self.cameras.append(cam)
       self.vipc_server.create_buffers(c.stream_type, 20, False, cam.W, cam.H)
@@ -63,6 +63,11 @@ class Camerad:
     for t in threads:
       t.join()
 
-if __name__ == "__main__":
+
+def main():
   camerad = Camerad()
   camerad.run()
+
+
+if __name__ == "__main__":
+  main()