Improve USB device reset logic

webrtc/tools/video_analysis.py

Index: webrtc/tools/video_analysis.py
diff --git a/webrtc/tools/run_video_analysis.py b/webrtc/tools/video_analysis.py
similarity index 89%
rename from webrtc/tools/run_video_analysis.py
rename to webrtc/tools/video_analysis.py
index 29682aa02917779742ececaca52b0662a6d80546..b13543d65a85ea1a57ccccf0b1b5397ddf02d0e5 100755
--- a/webrtc/tools/run_video_analysis.py
+++ b/webrtc/tools/video_analysis.py
@@ -7,14 +7,14 @@
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
+import glob
 import optparse
 import os
+import shutil
 import subprocess
 import sys
 import time
-import glob
-import re
-import shutil
+
 
 # Used to time-stamp output files and directories
 CURRENT_TIME = time.strftime("%d_%m_%Y-%H:%M:%S")
@@ -158,47 +158,67 @@ def CreateRecordingDirs(options):
   return record_paths
 
 
-def RestartMagewellDevices(ref_video_device, test_video_device):
-  """Reset the USB ports where Magewell capture devices are connected to.
+def FindUsbPortForV4lDevices(ref_video_device, test_video_device):
+  """Tries to find the usb port for ref_video_device and test_video_device.
 
   Tries to find the provided ref_video_device and test_video_device devices
   which use video4linux and then do a soft reset by using USB unbind and bind.
+
+  Args:
+    ref_device(string): reference recording device path.
+    test_device(string): test recording device path
+
+  Returns:
+    usb_ports(list): USB ports(string) for the devices found.
+  """
+
+  # Find the device location including USB and USB Bus ID's. Use the usb1
+  # in the path since the driver folder is a symlink which contains all the
+  # usb device port mappings and it's the same in all usbN folders. Tested
+  # on Ubuntu 14.04.
+  v4l_device_path = '/sys/bus/usb/devices/usb1/1-1/driver/**/**/video4linux/'
+  v4l_ref_device = glob.glob('%s%s' % (v4l_device_path, ref_video_device))
+  v4l_test_device = glob.glob('%s%s' % (v4l_device_path, test_video_device))
+  usb_ports = []
+  paths = []
+
+  # Split on the driver folder first since we are only interested in the
+  # folders thereafter.
+  ref_path = str(v4l_ref_device).split('driver')[1].split('/')
+  test_path = str(v4l_test_device).split('driver')[1].split('/')
+  paths.append(ref_path)
+  paths.append(test_path)
+
+  for path in paths:
+    for usb_id in path:
+      # Look for : separator and then use the first element in the list.
+      # E.g 3-3.1:1.0 split on : and [0] becomes 3-3.1 which can be used
+      # for bind/unbind.
+      if ':' in usb_id:
+        usb_ports.append(usb_id.split(':')[0])
+  return usb_ports
+
+
+def RestartMagewellDevices(ref_video_device_path, test_video_device_path):
+  """Reset the USB ports where Magewell capture devices are connected to.
+
+  Performs a soft reset by using USB unbind and bind.
   This is due to Magewell capture devices have proven to be unstable after the
   first recording attempt.
 
-  Args :
-    ref_video_device(string): reference recording device path.
-    test_video_device(string): test recording device path
+  Args:
+    ref_video_device_path(string): reference recording device path.
+    test_video_device_path(string): test recording device path
 
   Raises:
     MagewellError: If no magewell devices are found.
   """
 
   # Get the dev/videoN device name from the command line arguments.
-  ref_magewell = ref_video_device.split('/')[2]
-  test_magewell = test_video_device.split('/')[2]
-
-  # Find the device location including USB and USB Bus ID's.
-  device_string = '/sys/bus/usb/devices/usb*/**/**/video4linux/'
-  ref_magewell_device = glob.glob('%s%s' % (device_string, ref_magewell))
-  test_magewell_device = glob.glob('%s%s' % (device_string, test_magewell))
-
-  magewell_usb_ports = []
-
-  # Figure out the USB bus and port ID for each device.
-  ref_magewell_path = str(ref_magewell_device).split('/')
-  for directory in ref_magewell_path:
-    # Find the folder with pattern "N-N", e.g. "4-3" or \
-    # "[USB bus ID]-[USB port]"
-    if re.match(r'^\d-\d$', directory):
-      magewell_usb_ports.append(directory)
-
-  test_magewell_path = str(test_magewell_device).split('/')
-  for directory in test_magewell_path:
-    # Find the folder with pattern "N-N", e.g. "4-3" or \
-    # "[USB bus ID]-[USB port]"
-    if re.match(r'^\d-\d$', directory):
-      magewell_usb_ports.append(directory)
+  ref_magewell_path = ref_video_device_path.split('/')[2]
+  test_magewell_path = test_video_device_path.split('/')[2]
+  magewell_usb_ports = FindUsbPortForV4lDevices(ref_magewell_path,
+                                                test_magewell_path)
 
   # Abort early if no devices are found.
   if len(magewell_usb_ports) == 0:
@@ -413,7 +433,6 @@ def CompareVideos(options, cropped_ref_file, cropped_test_file):
       crop_height = param.split(':')[1]
 
   compare_cmd = [
-    sys.executable,
     compare_videos_script,
     '--ref_video', cropped_ref_file,
     '--test_video', cropped_test_file,