tools/video_analysis.py - src/webrtc - Git at Google

 #!/usr/bin/env python
 # Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # 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


 # Used to time-stamp output files and directories
 CURRENT_TIME = time.strftime("%d_%m_%Y-%H:%M:%S")


 class Error(Exception):
   pass


 class FfmpegError(Error):
   pass


 class MagewellError(Error):
   pass


 class CompareVideosError(Error):
   pass


 def _ParseArgs():
   """Registers the command-line options."""
   usage = 'usage: %prog [options]'
   parser = optparse.OptionParser(usage=usage)

   parser.add_option('--frame_width', type='int', default=1280,
                     help='Width of the recording. Default: %default')
   parser.add_option('--frame_height', type='int', default=720,
                     help='Height of the recording. Default: %default')
   parser.add_option('--framerate', type='int', default=60,
                     help='Recording framerate. Default: %default')
   parser.add_option('--ref_duration', type='int', default=20,
                     help='Reference recording duration. Default: %default')
   parser.add_option('--test_duration', type='int', default=10,
                     help='Test recording duration. Default: %default')
   parser.add_option('--time_between_recordings', type='int', default=5,
                     help='Time between starting test recording after ref.'
                     'Default: %default')
   parser.add_option('--ref_video_device', type='string', default='/dev/video0',
                     help='Reference recording device. Default: %default')
   parser.add_option('--test_video_device', type='string', default='/dev/video1',
                     help='Test recording device. Default: %default')
   parser.add_option('--app_name', type='string',
                     help='Name of the app under test.')
   parser.add_option('--recording_api', type='string', default='Video4Linux2',
                     help='Recording API to use. Default: %default')
   parser.add_option('--pixel_format', type='string', default='yuv420p',
                     help='Recording pixel format Default: %default')
   parser.add_option('--ffmpeg', type='string',
                     help='Path to the ffmpeg executable for the reference '
                     'device.')
   parser.add_option('--video_container', type='string', default='yuv',
                     help='Video container for the recordings.'
                     'Default: %default')
   parser.add_option('--compare_videos_script', type='string',
                     default='compare_videos.py',
                     help='Path to script used to compare and generate metrics.'
                     'Default: %default')
   parser.add_option('--frame_analyzer', type='string',
                     default='../../out/Default/frame_analyzer',
                     help='Path to the frame analyzer executable.'
                     'Default: %default')
   parser.add_option('--zxing_path', type='string',
                     help='Path to the zebra xing barcode analyzer.')
   parser.add_option('--ref_rec_dir', type='string', default='ref',
                     help='Path to where reference recordings will be created.'
                     'Ideally keep the ref and test directories on separate'
                     'drives. Default: %default')
   parser.add_option('--test_rec_dir', type='string', default='test',
                     help='Path to where test recordings will be created.'
                     'Ideally keep the ref and test directories on separate '
                     'drives. Default: %default')
   parser.add_option('--test_crop_parameters', type='string',
                     help='ffmpeg processing parameters for the test video.')
   parser.add_option('--ref_crop_parameters', type='string',
                     help='ffmpeg processing parameters for the ref video.')

   options, _ = parser.parse_args()

   if not options.app_name:
     parser.error('You must provide an application name!')

   if not options.test_crop_parameters or not options.ref_crop_parameters:
     parser.error('You must provide ref and test crop parameters!')

   # Ensure the crop filter is included in the crop parameters used for ffmpeg.
   if 'crop' not in options.ref_crop_parameters:
     parser.error('You must provide a reference crop filter for ffmpeg.')
   if 'crop' not in options.test_crop_parameters:
     parser.error('You must provide a test crop filter for ffmpeg.')

   if not options.ffmpeg:
     parser.error('You most provide location for the ffmpeg executable.')
   if not os.path.isfile(options.ffmpeg):
     parser.error('Cannot find the ffmpeg executable.')

   # compare_videos.py dependencies.
   if not os.path.isfile(options.compare_videos_script):
     parser.warning('Cannot find compare_videos.py script, no metrics will be '
                    'generated!')
   if not os.path.isfile(options.frame_analyzer):
     parser.warning('Cannot find frame_analyzer, no metrics will be generated!')
   if not os.path.isfile(options.zxing_path):
     parser.warning('Cannot find Zebra Xing, no metrics will be generated!')

   return options


 def CreateRecordingDirs(options):
   """Create root + sub directories for reference and test recordings.

   Args:
     options(object): Contains all the provided command line options.

   Returns:
     record_paths(dict): key: value pair with reference and test file
         absolute paths.
   """

   # Create root directories for the video recordings.
   if not os.path.isdir(options.ref_rec_dir):
     os.makedirs(options.ref_rec_dir)
   if not os.path.isdir(options.test_rec_dir):
     os.makedirs(options.test_rec_dir)

   # Create and time-stamp directories for all the output files.
   ref_rec_dir = os.path.join(options.ref_rec_dir, options.app_name + '_' + \
     CURRENT_TIME)
   test_rec_dir = os.path.join(options.test_rec_dir, options.app_name + '_' + \
     CURRENT_TIME)

   os.makedirs(ref_rec_dir)
   os.makedirs(test_rec_dir)

   record_paths = {
     'ref_rec_location' : os.path.abspath(ref_rec_dir),
     'test_rec_location' : os.path.abspath(test_rec_dir)
   }

   return record_paths


 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.
   try:
     ref_path = str(v4l_ref_device).split('driver')[1].split('/')
     test_path = str(v4l_test_device).split('driver')[1].split('/')
   except IndexError:
     print 'Could not find one or both of the specified recording devices.'
   else:
     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_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_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:
     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']
       bind_cmd = ['sudo', 'tee', '/sys/bus/usb/drivers/usb/bind']

       # TODO(jansson) Figure out a way to call on echo once for bind & unbind
       # if possible.
       echo_unbind = subprocess.Popen(echo_cmd, stdout=subprocess.PIPE)
       unbind = subprocess.Popen(unbind_cmd, stdin=echo_unbind.stdout)
       echo_unbind.stdout.close()
       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.wait()
   if bind.returncode == 0:
     print 'Reset done!\n'


 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.

   Returns:
     recording_files_and_time(dict): key: value pair with the path to cropped
         test and reference video files.

   Raises:
     FfmpegError: If the ffmpeg command fails.
   """
   ref_file_name = '%s_%s_ref.%s' % (options.app_name, CURRENT_TIME,
     options.video_container)
   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 = os.path.join(test_file_location, test_file_name)

   # Reference video recorder command line.
   ref_cmd = [
     options.ffmpeg,
     '-v', 'error',
     '-s', '%dx%d' % (options.frame_width, options.frame_height),
     '-r', '%d' % options.framerate,
     '-f', '%s' % options.recording_api,
     '-i', '%s' % options.ref_video_device,
     '-pix_fmt', '%s' % options.pixel_format,
     '-s', '%dx%d' % (options.frame_width, options.frame_height),
     '-t', '%d' % options.ref_duration,
     '-r', '%d' % options.framerate,
     ref_file
   ]

   # Test video recorder command line.
   test_cmd = [
     options.ffmpeg,
     '-v', 'error',
     '-s', '%dx%d' % (options.frame_width, options.frame_height),
     '-r', '%d' % options.framerate,
     '-f', '%s' % options.recording_api,
     '-i', '%s' % options.test_video_device,
     '-pix_fmt', '%s' % options.pixel_format,
     '-s', '%dx%d' % (options.frame_width, options.frame_height),
     '-t', '%d' % options.test_duration,
     '-r', '%d' % options.framerate,
     test_file
   ]
   print 'Trying to record from reference recorder...'
   ref_recorder = subprocess.Popen(ref_cmd)

   # Start the 2nd recording a little later to ensure the 1st one has started.
   # TODO(jansson) Check that the ref_recorder output file exists rather than
   # using sleep.
   time.sleep(options.time_between_recordings)
   print 'Trying to record from test recorder...'
   test_recorder = subprocess.Popen(test_cmd)
   test_recorder.wait()
   ref_recorder.wait()

   # ffmpeg does not abort when it fails, need to check return code.
   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,
                           ref_file_name, ref_file_location):
   """Performs a horizontal flip of the reference video to match the test video.

   This is done to the match orientation and then crops the ref and test videos
   using the options.test_crop_parameters and options.ref_crop_parameters.

   Args:
     options(object): Contains all the provided command line options.
     test_file_name(string): Name of the test video file recording.
     test_file_location(string): Path to the test video file recording.
     ref_file_name(string): Name of the reference video file recording.
     ref_file_location(string): Path to the reference video file recording.

   Returns:
     recording_files_and_time(dict): key: value pair with the path to cropped
         test and reference video files.

   Raises:
     FfmpegError: If the ffmpeg command fails.
   """
   print 'Trying to crop videos...'

   # Ref file cropping.
   cropped_ref_file_name = 'cropped_' + ref_file_name
   cropped_ref_file = os.path.abspath(
       os.path.join(ref_file_location, cropped_ref_file_name))

   ref_video_crop_cmd = [
     options.ffmpeg,
     '-v', 'error',
     '-s', '%dx%d' % (options.frame_width, options.frame_height),
     '-i', '%s' % os.path.join(ref_file_location, ref_file_name),
     '-vf', '%s' % options.ref_crop_parameters,
     '-c:a', 'copy',
     cropped_ref_file
   ]

   # Test file cropping.
   cropped_test_file_name = 'cropped_' + test_file_name
   cropped_test_file = os.path.abspath(
       os.path.join(test_file_location, cropped_test_file_name))

   test_video_crop_cmd = [
     options.ffmpeg,
     '-v', 'error',
     '-s', '%dx%d' % (options.frame_width, options.frame_height),
     '-i', '%s' % os.path.join(test_file_location, test_file_name),
     '-vf', '%s' % options.test_crop_parameters,
     '-c:a', 'copy',
     cropped_test_file
   ]

   ref_crop = subprocess.Popen(ref_video_crop_cmd)
   ref_crop.wait()
   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'

     # Need to return these so they can be used by other parts.
     cropped_recordings = {
       'cropped_test_file' : cropped_test_file,
       'cropped_ref_file' : cropped_ref_file
     }
     return cropped_recordings


 def CompareVideos(options, cropped_ref_file, cropped_test_file):
   """Runs the compare_video.py script from src/webrtc/tools using the file path.

   Uses the path from recording_result and writes the output to a file named
   <options.app_name + '_' + CURRENT_TIME + '_result.txt> in the reference video
   recording folder taken from recording_result.

   Args:
     options(object): Contains all the provided command line options.
     cropped_ref_file(string): Path to cropped reference video file.
     cropped_test_file(string): Path to cropped test video file.

   Raises:
     CompareVideosError: If compare_videos.py fails.
   """
   print 'Starting comparison...'
   print 'Grab a coffee, this might take a few minutes...'
   compare_videos_script = os.path.abspath(options.compare_videos_script)
   rec_path = os.path.abspath(os.path.join(
     os.path.dirname(cropped_test_file)))
   result_file_name = os.path.join(rec_path, '%s_%s_result.txt') % (
     options.app_name, CURRENT_TIME)

   # 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 = int(param.split(':')[0].split('=')[1])
       crop_height = int(param.split(':')[1])

   compare_cmd = [
     compare_videos_script,
     '--ref_video=%s' % cropped_ref_file,
     '--test_video=%s' % cropped_test_file,
     '--frame_analyzer=%s' % os.path.abspath(options.frame_analyzer),
     '--zxing_path=%s' % options.zxing_path,
     '--ffmpeg_path=%s' % options.ffmpeg,
     '--stats_file_ref=%s_stats.txt' %
         os.path.join(os.path.dirname(cropped_ref_file), cropped_ref_file),
     '--stats_file_test=%s_stats.txt' %
         os.path.join(os.path.dirname(cropped_test_file), cropped_test_file),
     '--yuv_frame_height=%d' % crop_height,
     '--yuv_frame_width=%d' % crop_width
   ]

   with open(result_file_name, 'w') as f:
     try:
       compare_video_recordings = subprocess.check_output(compare_cmd)
       f.write(compare_video_recordings)
     except subprocess.CalledProcessError as error:
       raise CompareVideosError('Failed to perform comparison: %s' % error)
     else:
       print 'Result recorded to: %s' % os.path.abspath(result_file_name)
       print 'Comparison done!'
       return compare_video_recordings


 def main():
   """The main function.

   A simple invocation is:
   ./run_video_analysis.py \
     --app_name AppRTCMobile \
     --ffmpeg ./ffmpeg --ref_video_device=/dev/video0 \
     --test_video_device=/dev/video1 \
     --zxing_path ./zxing \
     --test_crop_parameters 'crop=950:420:130:56' \
     --ref_crop_parameters 'hflip, crop=950:420:130:56' \
     --ref_rec_dir /tmp/ref \
     --test_rec_dir /tmp/test

   This will produce the following files if successful:
   # Original video recordings.
   /tmp/ref/AppRTCMobile_<recording date and time>_ref.yuv
   /tmp/test/AppRTCMobile_<recording date and time>_test.yuv

   # Cropped video recordings according to the crop parameters.
   /tmp/ref/cropped_AppRTCMobile_<recording date and time>_ref.yuv
   /tmp/test/cropped_AppRTCMobile_<recording date and time>_ref.yuv

   # Comparison metrics from cropped test and ref videos.
   /tmp/test/AppRTCMobile_<recording date and time>_result.text

   """
   options = _ParseArgs()
   RestartMagewellDevices(options.ref_video_device, options.test_video_device)
   record_paths = CreateRecordingDirs(options)
   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:
     CompareVideos(options, recording_result['cropped_ref_file'],
                   recording_result['cropped_test_file'])
   else:
     print ('Skipping compare videos step due to compare_videos flag were not '
            'passed.')


 if __name__ == '__main__':
   sys.exit(main())
	#!/usr/bin/env python
	# Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
	#
	# Use of this source code is governed by a BSD-style license
	# that can be found in the LICENSE file in the root of the source
	# tree. An additional intellectual property rights grant can be found
	# 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


	# Used to time-stamp output files and directories
	CURRENT_TIME = time.strftime("%d_%m_%Y-%H:%M:%S")


	class Error(Exception):
	pass


	class FfmpegError(Error):
	pass


	class MagewellError(Error):
	pass


	class CompareVideosError(Error):
	pass


	def _ParseArgs():
	"""Registers the command-line options."""
	usage = 'usage: %prog [options]'
	parser = optparse.OptionParser(usage=usage)

	parser.add_option('--frame_width', type='int', default=1280,
	help='Width of the recording. Default: %default')
	parser.add_option('--frame_height', type='int', default=720,
	help='Height of the recording. Default: %default')
	parser.add_option('--framerate', type='int', default=60,
	help='Recording framerate. Default: %default')
	parser.add_option('--ref_duration', type='int', default=20,
	help='Reference recording duration. Default: %default')
	parser.add_option('--test_duration', type='int', default=10,
	help='Test recording duration. Default: %default')
	parser.add_option('--time_between_recordings', type='int', default=5,
	help='Time between starting test recording after ref.'
	'Default: %default')
	parser.add_option('--ref_video_device', type='string', default='/dev/video0',
	help='Reference recording device. Default: %default')
	parser.add_option('--test_video_device', type='string', default='/dev/video1',
	help='Test recording device. Default: %default')
	parser.add_option('--app_name', type='string',
	help='Name of the app under test.')
	parser.add_option('--recording_api', type='string', default='Video4Linux2',
	help='Recording API to use. Default: %default')
	parser.add_option('--pixel_format', type='string', default='yuv420p',
	help='Recording pixel format Default: %default')
	parser.add_option('--ffmpeg', type='string',
	help='Path to the ffmpeg executable for the reference '
	'device.')
	parser.add_option('--video_container', type='string', default='yuv',
	help='Video container for the recordings.'
	'Default: %default')
	parser.add_option('--compare_videos_script', type='string',
	default='compare_videos.py',
	help='Path to script used to compare and generate metrics.'
	'Default: %default')
	parser.add_option('--frame_analyzer', type='string',
	default='../../out/Default/frame_analyzer',
	help='Path to the frame analyzer executable.'
	'Default: %default')
	parser.add_option('--zxing_path', type='string',
	help='Path to the zebra xing barcode analyzer.')
	parser.add_option('--ref_rec_dir', type='string', default='ref',
	help='Path to where reference recordings will be created.'
	'Ideally keep the ref and test directories on separate'
	'drives. Default: %default')
	parser.add_option('--test_rec_dir', type='string', default='test',
	help='Path to where test recordings will be created.'
	'Ideally keep the ref and test directories on separate '
	'drives. Default: %default')
	parser.add_option('--test_crop_parameters', type='string',
	help='ffmpeg processing parameters for the test video.')
	parser.add_option('--ref_crop_parameters', type='string',
	help='ffmpeg processing parameters for the ref video.')

	options, _ = parser.parse_args()

	if not options.app_name:
	parser.error('You must provide an application name!')

	if not options.test_crop_parameters or not options.ref_crop_parameters:
	parser.error('You must provide ref and test crop parameters!')

	# Ensure the crop filter is included in the crop parameters used for ffmpeg.
	if 'crop' not in options.ref_crop_parameters:
	parser.error('You must provide a reference crop filter for ffmpeg.')
	if 'crop' not in options.test_crop_parameters:
	parser.error('You must provide a test crop filter for ffmpeg.')

	if not options.ffmpeg:
	parser.error('You most provide location for the ffmpeg executable.')
	if not os.path.isfile(options.ffmpeg):
	parser.error('Cannot find the ffmpeg executable.')

	# compare_videos.py dependencies.
	if not os.path.isfile(options.compare_videos_script):
	parser.warning('Cannot find compare_videos.py script, no metrics will be '
	'generated!')
	if not os.path.isfile(options.frame_analyzer):
	parser.warning('Cannot find frame_analyzer, no metrics will be generated!')
	if not os.path.isfile(options.zxing_path):
	parser.warning('Cannot find Zebra Xing, no metrics will be generated!')

	return options


	def CreateRecordingDirs(options):
	"""Create root + sub directories for reference and test recordings.

	Args:
	options(object): Contains all the provided command line options.

	Returns:
	record_paths(dict): key: value pair with reference and test file
	absolute paths.
	"""

	# Create root directories for the video recordings.
	if not os.path.isdir(options.ref_rec_dir):
	os.makedirs(options.ref_rec_dir)
	if not os.path.isdir(options.test_rec_dir):
	os.makedirs(options.test_rec_dir)

	# Create and time-stamp directories for all the output files.
	ref_rec_dir = os.path.join(options.ref_rec_dir, options.app_name + '_' + \
	CURRENT_TIME)
	test_rec_dir = os.path.join(options.test_rec_dir, options.app_name + '_' + \
	CURRENT_TIME)

	os.makedirs(ref_rec_dir)
	os.makedirs(test_rec_dir)

	record_paths = {
	'ref_rec_location' : os.path.abspath(ref_rec_dir),
	'test_rec_location' : os.path.abspath(test_rec_dir)
	}

	return record_paths


	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.
	try:
	ref_path = str(v4l_ref_device).split('driver')[1].split('/')
	test_path = str(v4l_test_device).split('driver')[1].split('/')
	except IndexError:
	print 'Could not find one or both of the specified recording devices.'
	else:
	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_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_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:
	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']
	bind_cmd = ['sudo', 'tee', '/sys/bus/usb/drivers/usb/bind']

	# TODO(jansson) Figure out a way to call on echo once for bind & unbind
	# if possible.
	echo_unbind = subprocess.Popen(echo_cmd, stdout=subprocess.PIPE)
	unbind = subprocess.Popen(unbind_cmd, stdin=echo_unbind.stdout)
	echo_unbind.stdout.close()
	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.wait()
	if bind.returncode == 0:
	print 'Reset done!\n'


	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.

	Returns:
	recording_files_and_time(dict): key: value pair with the path to cropped
	test and reference video files.

	Raises:
	FfmpegError: If the ffmpeg command fails.
	"""
	ref_file_name = '%s_%s_ref.%s' % (options.app_name, CURRENT_TIME,
	options.video_container)
	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 = os.path.join(test_file_location, test_file_name)

	# Reference video recorder command line.
	ref_cmd = [
	options.ffmpeg,
	'-v', 'error',
	'-s', '%dx%d' % (options.frame_width, options.frame_height),
	'-r', '%d' % options.framerate,
	'-f', '%s' % options.recording_api,
	'-i', '%s' % options.ref_video_device,
	'-pix_fmt', '%s' % options.pixel_format,
	'-s', '%dx%d' % (options.frame_width, options.frame_height),
	'-t', '%d' % options.ref_duration,
	'-r', '%d' % options.framerate,
	ref_file
	]

	# Test video recorder command line.
	test_cmd = [
	options.ffmpeg,
	'-v', 'error',
	'-s', '%dx%d' % (options.frame_width, options.frame_height),
	'-r', '%d' % options.framerate,
	'-f', '%s' % options.recording_api,
	'-i', '%s' % options.test_video_device,
	'-pix_fmt', '%s' % options.pixel_format,
	'-s', '%dx%d' % (options.frame_width, options.frame_height),
	'-t', '%d' % options.test_duration,
	'-r', '%d' % options.framerate,
	test_file
	]
	print 'Trying to record from reference recorder...'
	ref_recorder = subprocess.Popen(ref_cmd)

	# Start the 2nd recording a little later to ensure the 1st one has started.
	# TODO(jansson) Check that the ref_recorder output file exists rather than
	# using sleep.
	time.sleep(options.time_between_recordings)
	print 'Trying to record from test recorder...'
	test_recorder = subprocess.Popen(test_cmd)
	test_recorder.wait()
	ref_recorder.wait()

	# ffmpeg does not abort when it fails, need to check return code.
	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,
	ref_file_name, ref_file_location):
	"""Performs a horizontal flip of the reference video to match the test video.

	This is done to the match orientation and then crops the ref and test videos
	using the options.test_crop_parameters and options.ref_crop_parameters.

	Args:
	options(object): Contains all the provided command line options.
	test_file_name(string): Name of the test video file recording.
	test_file_location(string): Path to the test video file recording.
	ref_file_name(string): Name of the reference video file recording.
	ref_file_location(string): Path to the reference video file recording.

	Returns:
	recording_files_and_time(dict): key: value pair with the path to cropped
	test and reference video files.

	Raises:
	FfmpegError: If the ffmpeg command fails.
	"""
	print 'Trying to crop videos...'

	# Ref file cropping.
	cropped_ref_file_name = 'cropped_' + ref_file_name
	cropped_ref_file = os.path.abspath(
	os.path.join(ref_file_location, cropped_ref_file_name))

	ref_video_crop_cmd = [
	options.ffmpeg,
	'-v', 'error',
	'-s', '%dx%d' % (options.frame_width, options.frame_height),
	'-i', '%s' % os.path.join(ref_file_location, ref_file_name),
	'-vf', '%s' % options.ref_crop_parameters,
	'-c:a', 'copy',
	cropped_ref_file
	]

	# Test file cropping.
	cropped_test_file_name = 'cropped_' + test_file_name
	cropped_test_file = os.path.abspath(
	os.path.join(test_file_location, cropped_test_file_name))

	test_video_crop_cmd = [
	options.ffmpeg,
	'-v', 'error',
	'-s', '%dx%d' % (options.frame_width, options.frame_height),
	'-i', '%s' % os.path.join(test_file_location, test_file_name),
	'-vf', '%s' % options.test_crop_parameters,
	'-c:a', 'copy',
	cropped_test_file
	]

	ref_crop = subprocess.Popen(ref_video_crop_cmd)
	ref_crop.wait()
	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'

	# Need to return these so they can be used by other parts.
	cropped_recordings = {
	'cropped_test_file' : cropped_test_file,
	'cropped_ref_file' : cropped_ref_file
	}
	return cropped_recordings


	def CompareVideos(options, cropped_ref_file, cropped_test_file):
	"""Runs the compare_video.py script from src/webrtc/tools using the file path.

	Uses the path from recording_result and writes the output to a file named
	<options.app_name + '_' + CURRENT_TIME + '_result.txt> in the reference video
	recording folder taken from recording_result.

	Args:
	options(object): Contains all the provided command line options.
	cropped_ref_file(string): Path to cropped reference video file.
	cropped_test_file(string): Path to cropped test video file.

	Raises:
	CompareVideosError: If compare_videos.py fails.
	"""
	print 'Starting comparison...'
	print 'Grab a coffee, this might take a few minutes...'
	compare_videos_script = os.path.abspath(options.compare_videos_script)
	rec_path = os.path.abspath(os.path.join(
	os.path.dirname(cropped_test_file)))
	result_file_name = os.path.join(rec_path, '%s_%s_result.txt') % (
	options.app_name, CURRENT_TIME)

	# 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 = int(param.split(':')[0].split('=')[1])
	crop_height = int(param.split(':')[1])

	compare_cmd = [
	compare_videos_script,
	'--ref_video=%s' % cropped_ref_file,
	'--test_video=%s' % cropped_test_file,
	'--frame_analyzer=%s' % os.path.abspath(options.frame_analyzer),
	'--zxing_path=%s' % options.zxing_path,
	'--ffmpeg_path=%s' % options.ffmpeg,
	'--stats_file_ref=%s_stats.txt' %
	os.path.join(os.path.dirname(cropped_ref_file), cropped_ref_file),
	'--stats_file_test=%s_stats.txt' %
	os.path.join(os.path.dirname(cropped_test_file), cropped_test_file),
	'--yuv_frame_height=%d' % crop_height,
	'--yuv_frame_width=%d' % crop_width
	]

	with open(result_file_name, 'w') as f:
	try:
	compare_video_recordings = subprocess.check_output(compare_cmd)
	f.write(compare_video_recordings)
	except subprocess.CalledProcessError as error:
	raise CompareVideosError('Failed to perform comparison: %s' % error)
	else:
	print 'Result recorded to: %s' % os.path.abspath(result_file_name)
	print 'Comparison done!'
	return compare_video_recordings


	def main():
	"""The main function.

	A simple invocation is:
	./run_video_analysis.py \
	--app_name AppRTCMobile \
	--ffmpeg ./ffmpeg --ref_video_device=/dev/video0 \
	--test_video_device=/dev/video1 \
	--zxing_path ./zxing \
	--test_crop_parameters 'crop=950:420:130:56' \
	--ref_crop_parameters 'hflip, crop=950:420:130:56' \
	--ref_rec_dir /tmp/ref \
	--test_rec_dir /tmp/test

	This will produce the following files if successful:
	# Original video recordings.
	/tmp/ref/AppRTCMobile_<recording date and time>_ref.yuv
	/tmp/test/AppRTCMobile_<recording date and time>_test.yuv

	# Cropped video recordings according to the crop parameters.
	/tmp/ref/cropped_AppRTCMobile_<recording date and time>_ref.yuv
	/tmp/test/cropped_AppRTCMobile_<recording date and time>_ref.yuv

	# Comparison metrics from cropped test and ref videos.
	/tmp/test/AppRTCMobile_<recording date and time>_result.text

	"""
	options = _ParseArgs()
	RestartMagewellDevices(options.ref_video_device, options.test_video_device)
	record_paths = CreateRecordingDirs(options)
	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:
	CompareVideos(options, recording_result['cropped_ref_file'],
	recording_result['cropped_test_file'])
	else:
	print ('Skipping compare videos step due to compare_videos flag were not '
	'passed.')


	if __name__ == '__main__':
	sys.exit(main())