Improve error handling for ffmpeg operations

webrtc/tools/run_video_analysis.py

Index: webrtc/tools/run_video_analysis.py
diff --git a/webrtc/tools/run_video_analysis.py b/webrtc/tools/run_video_analysis.py
index 350bc556fb71cd4a461639eb045d14432133a85b..f133c7d93c0d955a100d6453f855b305fd9e7498 100755
--- a/webrtc/tools/run_video_analysis.py
+++ b/webrtc/tools/run_video_analysis.py
@@ -14,10 +14,24 @@ 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")
 
+# Base error class.

[kjellander_webrtc, 2017/03/15 11:51:00]

Please skip the comment for each of these classes. They don't add any value.

[janssonWebRTC, 2017/03/15 13:44:36]

Done.

+class Error(Exception):
+  pass
+
+# FFMpeg related error class.
+class FfmpegError(Error):
+  pass
+
+# Magewell related error class.
+class MagewellError(Error):
+  pass
+
+
 def _ParseArgs():
   """Registers the command-line options."""
   usage = 'usage: %prog [options]'
@@ -166,7 +180,6 @@ def RestartMagewellDevices(ref_video_device, test_video_device):
   # 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):
@@ -174,17 +187,18 @@ def RestartMagewellDevices(ref_video_device, test_video_device):
 
   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)
 
-  print '\nResetting USB ports where magewell devices are connected...'
-
-  # Use the USB bus and port ID (e.g. 4-3) to unbind and bind the USB devices
-  # (i.e. soft eject and insert).
-  try:
+  # Abort early if no devices are found.
+  if len(magewell_usb_ports) == 0:
+    raise MagewellError('No magewell devices found.')
+  else:
+    print '\nResetting USB ports where magewell devices are connected...'
+    # Use the USB bus and port ID (e.g. 4-3) to unbind and bind the USB devices
+    # (i.e. soft eject and insert).
     for usb_port in magewell_usb_ports:
       echo_cmd = ['echo', usb_port]
       unbind_cmd = ['sudo', 'tee', '/sys/bus/usb/drivers/usb/unbind']
@@ -195,38 +209,35 @@ def RestartMagewellDevices(ref_video_device, test_video_device):
       echo_unbind = subprocess.Popen(echo_cmd, stdout=subprocess.PIPE)
       unbind = subprocess.Popen(unbind_cmd, stdin=echo_unbind.stdout)
       echo_unbind.stdout.close()
-      unbind.communicate()
       unbind.wait()
 
       echo_bind = subprocess.Popen(echo_cmd, stdout=subprocess.PIPE)
       bind = subprocess.Popen(bind_cmd, stdin=echo_bind.stdout)
       echo_bind.stdout.close()
-      bind.communicate()
       bind.wait()
-  except OSError as e:
-    print 'Error while resetting magewell devices: ' + e
-    raise
+  if bind.returncode == 0:
+    print 'Reset done!\n'
 
-  print 'Reset done!\n'
 
-
-def StartRecording(options, record_paths):
+def StartRecording(options, ref_file_location, test_file_location):
   """Starts recording from the two specified video devices.
 
   Args:
     options(object): Contains all the provided command line options.
     record_paths(dict): key: value pair with reference and test file
         absolute paths.
+  Return:

[kjellander_webrtc, 2017/03/15 11:51:00]

nit: You should document the potentially raised FfmpegError as well.

[janssonWebRTC, 2017/03/15 13:44:36]

Done.

+    FlipAndCropRecordings(function): Performs cropping and transforms on the

[kjellander_webrtc, 2017/03/15 11:51:00]

This is actually not true, what is returned from this function is the result
from the FlipAndCropRecordings function that is invoked on line 293 (the
cropped_recordings dict).

[janssonWebRTC, 2017/03/15 13:44:36]

Right, was a bit unsure of what to document since it was documented in the
FlipAnDCropRecordings function. Fixed.

+        reference and test recordings and returns the path for each
+        respectively.
   """
   ref_file_name = '%s_%s_ref.%s' % (options.app_name, CURRENT_TIME,
     options.video_container)
-  ref_file_location = os.path.join(record_paths['ref_rec_location'],
-      ref_file_name)
+  ref_file = os.path.join(ref_file_location, ref_file_name)
 
   test_file_name = '%s_%s_test.%s' % (options.app_name, CURRENT_TIME,
     options.video_container)
-  test_file_location = os.path.join(record_paths['test_rec_location'],
-      test_file_name)
+  test_file = os.path.join(test_file_location, test_file_name)
 
   # Reference video recorder command line.
   ref_cmd = [
@@ -240,7 +251,7 @@ def StartRecording(options, record_paths):
     '-s', options.frame_width + 'x' + options.frame_height,
     '-t', options.ref_duration,
     '-framerate', options.framerate,
-    ref_file_location
+    ref_file
   ]
 
   # Test video recorder command line.
@@ -255,7 +266,7 @@ def StartRecording(options, record_paths):
     '-s', options.frame_width + 'x' + options.frame_height,
     '-t', options.test_duration,
     '-framerate', options.framerate,
-    test_file_location
+    test_file
   ]
   print 'Trying to record from reference recorder...'
   ref_recorder = subprocess.Popen(ref_cmd, stderr=sys.stderr)
@@ -270,19 +281,17 @@ def StartRecording(options, record_paths):
   ref_recorder.wait()
 
   # ffmpeg does not abort when it fails, need to check return code.
-  assert ref_recorder.returncode == 0, (
-    'Ref recording failed, check ffmpeg output and device: %s'
-    % options.ref_video_device)
-  assert test_recorder.returncode == 0, (
-    'Test recording failed, check ffmpeg output and device: %s'
-    % options.test_video_device)
-
-  print 'Ref file recorded to: ' + os.path.abspath(ref_file_location)
-  print 'Test file recorded to: ' + os.path.abspath(test_file_location)
-  print 'Recording done!\n'
-  return FlipAndCropRecordings(options, test_file_name,
-    record_paths['test_rec_location'], ref_file_name,
-    record_paths['ref_rec_location'])
+  if ref_recorder.returncode != 0 or test_recorder.returncode != 0:
+    # Cleanup recording directories.
+    shutil.rmtree(ref_file_location)
+    shutil.rmtree(test_file_location)
+    raise FfmpegError('Recording failed, check ffmpeg output.')
+  else:
+    print 'Ref file recorded to: ' + os.path.abspath(ref_file)
+    print 'Test file recorded to: ' + os.path.abspath(test_file)
+    print 'Recording done!\n'
+    return FlipAndCropRecordings(options, test_file_name, test_file_location,
+        ref_file_name, ref_file_location)
 
 
 def FlipAndCropRecordings(options, test_file_name, test_file_location,
@@ -336,11 +345,17 @@ def FlipAndCropRecordings(options, test_file_name, test_file_location,
 
   ref_crop = subprocess.Popen(ref_video_crop_cmd)
   ref_crop.wait()
-  print 'Ref file cropped to: ' + cropped_ref_file
+  test_crop = subprocess.Popen(test_video_crop_cmd)
+  test_crop.wait()
 
-  try:
-    test_crop = subprocess.Popen(test_video_crop_cmd)
-    test_crop.wait()
+  # ffmpeg does not abort when it fails, need to check return code.
+  if ref_crop.returncode != 0 or test_crop.returncode != 0:
+    # Cleanup recording directories.
+    shutil.rmtree(ref_file_location)
+    shutil.rmtree(test_file_location)
+    raise FfmpegError('Cropping failed, check ffmpeg output.')
+  else:
+    print 'Ref file cropped to: ' + cropped_ref_file
     print 'Test file cropped to: ' + cropped_test_file
     print 'Cropping done!\n'
 
@@ -349,11 +364,7 @@ def FlipAndCropRecordings(options, test_file_name, test_file_location,
       'cropped_test_file' : cropped_test_file,
       'cropped_ref_file' : cropped_ref_file
     }
-
     return cropped_recordings
-  except subprocess.CalledProcessError as e:
-    print 'Something went wrong during cropping: ' + e
-    raise
 
 
 def CompareVideos(options, recording_result):
@@ -378,8 +389,8 @@ def CompareVideos(options, recording_result):
   result_file_name = os.path.join(rec_path, '%s_%s_result.txt') % (
     options.app_name, CURRENT_TIME)
 
-  # Find the crop dimensions (950 and 420) in the ref crop parameter string:
-  # 'hflip, crop=950:420:130:56'
+  # Find the crop dimensions (e.g. 950 and 420) in the ref crop parameter
+  # string: 'hflip, crop=950:420:130:56'
   for param in options.ref_crop_parameters.split('crop'):
     if param[0] == '=':
       crop_width = param.split(':')[0].split('=')[1]
@@ -405,11 +416,12 @@ def CompareVideos(options, recording_result):
     with open(result_file_name, 'w') as f:
       compare_video_recordings = subprocess.Popen(compare_cmd, stdout=f)
       compare_video_recordings.wait()
-      print 'Result recorded to: ' + os.path.abspath(result_file_name)
-      print 'Comparison done!'
-  except subprocess.CalledProcessError as e:
+  except OSError as e:
     print 'Something went wrong when trying to compare videos: ' + e
     raise
+  else:
+    print 'Result recorded to: ' + os.path.abspath(result_file_name)
+    print 'Comparison done!'
 
 
 def main():
@@ -442,7 +454,8 @@ def main():
   options = _ParseArgs()
   RestartMagewellDevices(options.ref_video_device, options.test_video_device)
   record_paths = CreateRecordingDirs(options)
-  recording_result = StartRecording(options, record_paths)
+  recording_result = StartRecording(options, record_paths['ref_rec_location'],
+                                    record_paths['test_rec_location'])
 
   # Do not require compare_video.py script to run, no metrics will be generated.
   if options.compare_videos_script: