Exemplo n.º 1
0
  def __init__(self, report_file_path, class_names_file_path,
               smooth_probs=False, smoothing_factor=16):
    class_name_map = IO.read_class_names(class_names_file_path)

    class_header_names = [class_name + '_probability'
                          for class_name in class_name_map.values()]

    header_mask = ['frame_number', 'frame_timestamp', 'qa_flag']
    header_mask.extend(class_header_names)

    report_header, report_data, data_col_range = IO.read_report(
      report_file_path, frame_col_num=1, timestamp_col_num=2, qa_flag_col_num=3,
      header_mask=header_mask, return_data_col_range=True)

    report_frame_numbers = report_data['frame_numbers']
    report_frame_numbers = report_frame_numbers.astype(np.int32)

    try:
      report_timestamps = report_data['frame_timestamps']
      report_timestamps = report_timestamps.astype(np.int32)
      qa_flags = report_data['qa_flag']
    except:
      report_timestamps = None
      qa_flags = None

    report_probs = report_data['probabilities']
    report_probs = report_probs.astype(np.float32)

    if smooth_probs:
      report_probs = IO.smooth_probs(report_probs, smoothing_factor)

    Trip.__init__(self, report_frame_numbers, report_timestamps, qa_flags,
                  report_probs, class_name_map)
Exemplo n.º 2
0
Arquivo: snva.py Projeto: fabat01/SNVA
async def main():
    logging.info('entering snva {} main process'.format(snva_version_string))

    # total_num_video_to_process = None

    def interrupt_handler(signal_number, _):
        logging.warning('Main process received interrupt signal '
                        '{}.'.format(signal_number))
        main_interrupt_queue.put_nowait('_')

        # if total_num_video_to_process is None \
        #     or total_num_video_to_process == len(video_file_paths):

        # Signal the logging thread to finish up
        logging.debug('signaling logger thread to end service.')

        log_queue.put_nowait(None)

        logger_thread.join()

        logging.shutdown()

    signal.signal(signal.SIGINT, interrupt_handler)

    try:
        ffmpeg_path = os.environ['FFMPEG_HOME']
    except KeyError:
        logging.warning('Environment variable FFMPEG_HOME not set. Attempting '
                        'to use default ffmpeg binary location.')
        if platform.system() == 'Windows':
            ffmpeg_path = 'ffmpeg.exe'
        else:
            ffmpeg_path = '/usr/local/bin/ffmpeg'

            if not path.exists(ffmpeg_path):
                ffmpeg_path = '/usr/bin/ffmpeg'

    logging.debug('FFMPEG path set to: {}'.format(ffmpeg_path))

    try:
        ffprobe_path = os.environ['FFPROBE_HOME']
    except KeyError:
        logging.warning('Environment variable FFPROBE_HOME not set. '
                        'Attempting to use default ffprobe binary location.')
        if platform.system() == 'Windows':
            ffprobe_path = 'ffprobe.exe'
        else:
            ffprobe_path = '/usr/local/bin/ffprobe'

            if not path.exists(ffprobe_path):
                ffprobe_path = '/usr/bin/ffprobe'

    logging.debug('FFPROBE path set to: {}'.format(ffprobe_path))

    # # TODO validate all video file paths in the provided text file if args.inputpath is a text file
    # if path.isdir(args.inputpath):
    #   video_file_names = set(IO.read_video_file_names(args.inputpath))
    #   video_file_paths = [path.join(args.inputpath, video_file_name)
    #                       for video_file_name in video_file_names]
    # elif path.isfile(args.inputpath):
    #   if args.inputpath[-3:] == 'txt':
    #     if args.inputlistrootdirpath is None:
    #       raise ValueError('--inputlistrootdirpath must be specified when using a'
    #                        ' text file as the input.')
    #     with open(args.inputpath, newline='') as input_file:
    #       video_file_paths = []
    #
    #       for line in input_file.readlines():
    #         line = line.rstrip()
    #         video_file_path = line.lstrip(args.inputlistrootdirpath)
    #         video_file_path = path.join('/media/root', video_file_path)
    #
    #         if path.isfile(video_file_path):
    #           video_file_paths.append(video_file_path)
    #         else:
    #           logging.warning('The video file at host path {} could not be found '
    #                           'at mapped path {} and will not be processed'.
    #             format(line, video_file_path))
    #   else:
    #     video_file_paths = [args.inputpath]
    # else:
    #   raise ValueError('The video file/folder specified at the path {} could '
    #                    'not be found.'.format(args.inputpath))

    models_root_dir_path = path.join(snva_home, args.modelsdirpath)

    models_dir_path = path.join(models_root_dir_path, args.modelname)

    logging.debug('models_dir_path set to {}'.format(models_dir_path))

    # model_file_path = path.join(models_dir_path, args.protobuffilename)
    #
    # if not path.isfile(model_file_path):
    #   raise ValueError('The model specified at the path {} could not be '
    #                    'found.'.format(model_file_path))
    #
    # logging.debug('model_file_path set to {}'.format(model_file_path))

    model_input_size_file_path = path.join(models_dir_path, 'input_size.txt')

    if not path.isfile(model_input_size_file_path):
        raise ValueError(
            'The model input size file specified at the path {} '
            'could not be found.'.format(model_input_size_file_path))

    logging.debug('model_input_size_file_path set to {}'.format(
        model_input_size_file_path))

    with open(model_input_size_file_path) as file:
        model_input_size_string = file.readline().rstrip()

        valid_size_set = ['224', '299']

        if model_input_size_string not in valid_size_set:
            raise ValueError(
                'The model input size is not in the set {}.'.format(
                    valid_size_set))

        model_input_size = int(model_input_size_string)

    # if logpath is the default value, expand it using the SNVA_HOME prefix,
    # otherwise, use the value explicitly passed by the user
    if args.outputpath == 'reports':
        output_dir_path = path.join(snva_home, args.outputpath)
    else:
        output_dir_path = args.outputpath
    logging.info("Output path set to: {}".format(output_dir_path))
    if not path.isdir(output_dir_path):
        os.makedirs(output_dir_path)

    if args.classnamesfilepath is None \
        or not path.isfile(args.classnamesfilepath):
        class_names_path = path.join(models_root_dir_path, 'class_names.txt')
    else:
        class_names_path = args.classnamesfilepath
    logging.debug('labels path set to: {}'.format(class_names_path))

    num_processes = args.numprocesses

    class_name_map = IO.read_class_names(class_names_path)

    return_code_queue_map = {}
    child_logger_thread_map = {}
    child_process_map = {}

    total_num_processed_videos = 0
    total_num_processed_frames = 0
    total_analysis_duration = 0

    def start_video_processor(video_file_path):
        # Before popping the next video off of the list and creating a process to
        # scan it, check to see if fewer than logical_device_count + 1 processes are
        # active. If not, Wait for a child process to release its semaphore
        # acquisition. If so, acquire the semaphore, pop the next video name,
        # create the next child process, and pass the semaphore to it
        return_code_queue = Queue()

        return_code_queue_map[video_file_path] = return_code_queue

        logging.debug('creating new child process.')

        child_log_queue = Queue()

        child_logger_thread = Thread(target=child_logger_fn,
                                     args=(log_queue, child_log_queue))

        child_logger_thread.start()

        child_logger_thread_map[video_file_path] = child_logger_thread

        if 'signalstate' == args.processormode:
            child_process = Process(
                target=process_video_signalstate,
                name=path.splitext(path.split(video_file_path)[1])[0],
                args=(video_file_path, output_dir_path, class_name_map,
                      args.modelname, args.modelsignaturename,
                      args.modelserverhost, model_input_size,
                      return_code_queue, child_log_queue, log_level,
                      ffmpeg_path, ffprobe_path, args.crop, args.cropwidth,
                      args.cropheight, args.cropx, args.cropy,
                      args.extracttimestamps, args.timestampmaxwidth,
                      args.timestampheight, args.timestampx, args.timestampy,
                      args.deinterlace, args.numchannels, args.batchsize,
                      args.smoothprobs, args.smoothingfactor,
                      args.binarizeprobs, args.writebbox,
                      args.writeeventreports, args.maxanalyzerthreads,
                      args.processormode))
        else:
            child_process = Process(
                target=process_video,
                name=path.splitext(path.split(video_file_path)[1])[0],
                args=(video_file_path, output_dir_path, class_name_map,
                      args.modelname, args.modelsignaturename,
                      args.modelserverhost, model_input_size,
                      return_code_queue, child_log_queue, log_level,
                      ffmpeg_path, ffprobe_path, args.crop, args.cropwidth,
                      args.cropheight, args.cropx, args.cropy,
                      args.extracttimestamps, args.timestampmaxwidth,
                      args.timestampheight, args.timestampx, args.timestampy,
                      args.deinterlace, args.numchannels, args.batchsize,
                      args.smoothprobs, args.smoothingfactor,
                      args.binarizeprobs, args.writeinferencereports,
                      args.writeeventreports, args.maxanalyzerthreads,
                      args.processormode))
        logging.debug('starting child process.')

        child_process.start()

        child_process_map[video_file_path] = child_process

    async def close_completed_video_processors(total_num_processed_videos,
                                               total_num_processed_frames,
                                               total_analysis_duration,
                                               websocket_conn):
        for video_file_path in list(return_code_queue_map.keys()):
            return_code_queue = return_code_queue_map[video_file_path]

            try:
                return_code_map = return_code_queue.get_nowait()

                return_code = return_code_map['return_code']
                return_value = return_code_map['return_value']

                child_process = child_process_map[video_file_path]

                logging.debug(
                    'child process {} returned with exit code {} and exit value '
                    '{}'.format(child_process.pid, return_code, return_value))

                if return_code == 'success':
                    total_num_processed_videos += 1
                    total_num_processed_frames += return_value
                    total_analysis_duration += return_code_map[
                        'analysis_duration']

                    logging.info('notifying control node of completion')

                    complete_request = json.dumps({
                        'action':
                        'COMPLETE',
                        'video':
                        os.path.basename(video_file_path),
                        'output':
                        return_code_map['output_locations']
                    })
                    await websocket_conn.send(complete_request)

                child_logger_thread = child_logger_thread_map[video_file_path]

                logging.debug(
                    'joining logger thread for child process {}'.format(
                        child_process.pid))

                child_logger_thread.join(timeout=15)

                if child_logger_thread.is_alive():
                    logging.warning(
                        'logger thread for child process {} remained alive following join '
                        'timeout'.format(child_process.pid))

                logging.debug('joining child process {}'.format(
                    child_process.pid))

                child_process.join(timeout=15)

                # if the child process has not yet terminated, kill the child process at
                # the risk of losing any log message not yet buffered by the main logger
                try:
                    os.kill(child_process.pid, signal.SIGKILL)
                    logging.warning(
                        'child process {} remained alive following join timeout and had to '
                        'be killed'.format(child_process.pid))
                except:
                    pass

                return_code_queue.close()

                return_code_queue_map.pop(video_file_path)
                child_logger_thread_map.pop(video_file_path)
                child_process_map.pop(video_file_path)
            except Empty:
                pass

        return total_num_processed_videos, total_num_processed_frames, \
               total_analysis_duration

    start = time()

    sleep_duration = 1
    breakLoop = False
    connectionId = None
    isIdle = False
    while True:
        try:
            if breakLoop:
                break
            wsUrl = 'ws://' + args.controlnodehost + '/registerProcess'
            if connectionId is not None:
                wsUrl = wsUrl + '?id=' + connectionId
            logging.debug("Connecting with URL {}".format(wsUrl))
            async with ws.connect(wsUrl) as conn:
                response = await conn.recv()
                response = json.loads(response)
                logging.info(response)

                if response['action'] != 'CONNECTION_SUCCESS':
                    raise ConnectionError(
                        'control node connection failed with response: {}'.
                        format(response))
                if connectionId is None:
                    connectionId = response['id']
                logging.debug("Assigned id {}".format(connectionId))
                while True:
                    # block if num_processes child processes are active
                    while len(return_code_queue_map) >= num_processes:
                        total_num_processed_videos, total_num_processed_frames, \
                        total_analysis_duration = await close_completed_video_processors(
                          total_num_processed_videos, total_num_processed_frames,
                          total_analysis_duration, conn)
                        sleep(sleep_duration)

                    try:  # todo poll for termination signal from control node
                        _ = main_interrupt_queue.get_nowait()
                        logging.debug(
                            'breaking out of child process generation following interrupt signal'
                        )
                        break
                    except:
                        pass

                    if not isIdle:
                        logging.info('requesting video')
                        request = json.dumps({'action': 'REQUEST_VIDEO'})
                        await conn.send(request)
                        logging.info('reading response')
                        response = await conn.recv()
                    else:
                        # If idle, we will try to close completed processors until all are done
                        while len(return_code_queue_map) > 0:
                            # Before checking for completed processes, check for a new message
                            logging.info('Checking for new message')
                            try:
                                # If we get a response quickly, break our waiting loop and process the command
                                response = await asyncio.wait_for(
                                    conn.recv(), 1)
                                break
                            except asyncio.TimeoutError:
                                # Otherwise, go back to finishing our current tasks
                                logging.debug(
                                    'No new message from control node, continuing...'
                                )
                                pass
                            total_num_processed_videos, total_num_processed_frames, \
                            total_analysis_duration = await close_completed_video_processors(
                              total_num_processed_videos, total_num_processed_frames,
                              total_analysis_duration, conn)
                            # by now, the last device_id_queue_len videos are being processed,
                            # so we can afford to poll for their completion infrequently
                            if len(return_code_queue_map) > 0:
                                sleep(sleep_duration)
                        # Once all are complete, if still idle we have no work left to do - we just wait for a new message
                        response = await conn.recv()

                    response = json.loads(response)

                    if response['action'] == 'STATUS_REQUEST':
                        logging.info('control node requested status request')
                        pass
                    elif response['action'] == 'CEASE_REQUESTS':
                        logging.info(
                            'control node has no more videos to process')
                        isIdle = True
                        pass
                    elif response['action'] == 'RESUME_REQUESTS':
                        logging.info(
                            'control node has instructed to resume requests')
                        isIdle = False
                        pass
                    elif response['action'] == 'SHUTDOWN':
                        logging.info('control node requested shutdown')
                        breakLoop = True
                        break
                    elif response['action'] == 'PROCESS':
                        # TODO Prepend input path
                        video_file_path = os.path.join(args.inputpath,
                                                       response['path'])
                        request_received = json.dumps({
                            'action': 'REQUEST_RECEIVED',
                            'video': response['path']
                        })
                        await conn.send(request_received)
                        try:
                            start_video_processor(video_file_path)
                        except Exception as e:
                            logging.error(
                                'an unknown error has occured while processing {}'
                                .format(video_file_path))
                            logging.error(e)
                    else:
                        raise ConnectionError(
                            'control node replied with unexpected response: {}'
                            .format(response))
                logging.debug('{} child processes remain enqueued'.format(
                    len(return_code_queue_map)))
                while len(return_code_queue_map) > 0:
                    #logging.debug('waiting for the final {} child processes to '
                    #              'terminate'.format(len(return_code_queue_map)))

                    total_num_processed_videos, total_num_processed_frames, \
                    total_analysis_duration = await close_completed_video_processors(
                      total_num_processed_videos, total_num_processed_frames,
                      total_analysis_duration, conn)

                    # by now, the last device_id_queue_len videos are being processed,
                    # so we can afford to poll for their completion infrequently
                    if len(return_code_queue_map) > 0:
                        #logging.debug('sleeping for {} seconds'.format(sleep_duration))
                        sleep(sleep_duration)

                end = time() - start

                processing_duration = IO.get_processing_duration(
                    end,
                    'snva {} processed a total of {} videos and {} frames in:'.
                    format(snva_version_string, total_num_processed_videos,
                           total_num_processed_frames))
                logging.info(processing_duration)

                logging.info(
                    'Video analysis alone spanned a cumulative {:.02f} '
                    'seconds'.format(total_analysis_duration))

                logging.info(
                    'exiting snva {} main process'.format(snva_version_string))
                breakLoop = True
        except socket.gaierror:
            # log something
            logging.info('gaierror')
            continue
        except ConnectionRefusedError:
            # log something else
            logging.info('connection refused')
            break
        except ws.exceptions.ConnectionClosed:
            logging.info('Connection lost.  Attempting reconnect...')
            continue
        except Exception as e:
            logging.error("Unknown Exception")
            logging.error(e)
            raise e
        if breakLoop:
            break
Exemplo n.º 3
0
def main():
  logging.info('entering snva {} main process'.format(snva_version_string))

  total_num_video_to_process = None

  def interrupt_handler(signal_number, _):
    logging.warning('Main process received interrupt signal '
                    '{}.'.format(signal_number))
    main_interrupt_queue.put_nowait('_')

    if total_num_video_to_process is None \
        or total_num_video_to_process == len(video_file_paths):

      # Signal the logging thread to finish up
      logging.debug('signaling logger thread to end service.')

      log_queue.put_nowait(None)

      logger_thread.join()

      logging.shutdown()

  signal.signal(signal.SIGINT, interrupt_handler)

  try:
    ffmpeg_path = os.environ['FFMPEG_HOME']
  except KeyError:
    logging.warning('Environment variable FFMPEG_HOME not set. Attempting '
                    'to use default ffmpeg binary location.')
    if platform.system() == 'Windows':
      ffmpeg_path = 'ffmpeg.exe'
    else:
      ffmpeg_path = '/usr/local/bin/ffmpeg'

      if not path.exists(ffmpeg_path):
        ffmpeg_path = '/usr/bin/ffmpeg'

  logging.debug('FFMPEG path set to: {}'.format(ffmpeg_path))

  try:
    ffprobe_path = os.environ['FFPROBE_HOME']
  except KeyError:
    logging.warning('Environment variable FFPROBE_HOME not set. '
                    'Attempting to use default ffprobe binary location.')
    if platform.system() == 'Windows':
      ffprobe_path = 'ffprobe.exe'
    else:
      ffprobe_path = '/usr/local/bin/ffprobe'

      if not path.exists(ffprobe_path):
        ffprobe_path = '/usr/bin/ffprobe'

  logging.debug('FFPROBE path set to: {}'.format(ffprobe_path))

  # TODO validate all video file paths in the provided text file if args.inputpath is a text file
  if path.isdir(args.inputpath):
    video_file_names = set(IO.read_video_file_names(args.inputpath))
    video_file_paths = [path.join(args.inputpath, video_file_name)
                        for video_file_name in video_file_names]
  elif path.isfile(args.inputpath):
    if args.inputpath[-3:] == 'txt':
      if args.inputlistrootdirpath is None:
        raise ValueError('--inputlistrootdirpath must be specified when using a'
                         ' text file as the input.')
      with open(args.inputpath, newline='') as input_file:
        video_file_paths = []

        for line in input_file.readlines():
          line = line.rstrip()
          video_file_path = line.lstrip(args.inputlistrootdirpath)
          video_file_path = path.join('/media/root', video_file_path)

          if path.isfile(video_file_path):
            video_file_paths.append(video_file_path)
          else:
            logging.warning('The video file at host path {} could not be found '
                            'at mapped path {} and will not be processed'.
              format(line, video_file_path))
    else:
      video_file_paths = [args.inputpath]
  else:
    raise ValueError('The video file/folder specified at the path {} could '
                     'not be found.'.format(args.inputpath))

  models_root_dir_path = path.join(snva_home, args.modelsdirpath)

  models_dir_path = path.join(models_root_dir_path, args.modelname)

  logging.debug('models_dir_path set to {}'.format(models_dir_path))

  model_file_path = path.join(models_dir_path, args.protobuffilename)

  if not path.isfile(model_file_path):
    raise ValueError('The model specified at the path {} could not be '
                     'found.'.format(model_file_path))

  logging.debug('model_file_path set to {}'.format(model_file_path))

  model_input_size_file_path = path.join(models_dir_path, 'input_size.txt')

  if not path.isfile(model_input_size_file_path):
    raise ValueError('The model input size file specified at the path {} '
                     'could not be found.'.format(model_input_size_file_path))

  logging.debug('model_input_size_file_path set to {}'.format(
    model_input_size_file_path))

  with open(model_input_size_file_path) as file:
    model_input_size_string = file.readline().rstrip()

    valid_size_set = ['224', '299']

    if model_input_size_string not in valid_size_set:
      raise ValueError('The model input size is not in the set {}.'.format(
        valid_size_set))

    model_input_size = int(model_input_size_string)

  # if logpath is the default value, expand it using the SNVA_HOME prefix,
  # otherwise, use the value explicitly passed by the user
  if args.outputpath == 'reports':
    output_dir_path = path.join(snva_home, args.outputpath)
  else:
    output_dir_path = args.outputpath

  if not path.isdir(output_dir_path):
    os.makedirs(output_dir_path)

  if args.excludepreviouslyprocessed:
    inference_report_dir_path = path.join(output_dir_path, 'inference_reports')

    if args.writeinferencereports and path.isdir(inference_report_dir_path):
      inference_report_file_names = os.listdir(inference_report_dir_path)
      inference_report_file_names = [path.splitext(name)[0]
                                     for name in inference_report_file_names]
      print('previously generated inference reports: {}'.format(
        inference_report_file_names))
    else:
      inference_report_file_names = None
    event_report_dir_path = path.join(output_dir_path, 'event_reports')

    if args.writeeventreports and path.isdir(event_report_dir_path):
      event_report_file_names = os.listdir(event_report_dir_path)
      event_report_file_names = [path.splitext(name)[0]
                                 for name in event_report_file_names]
      print('previously generated event reports: {}'.format(
        event_report_file_names))
    else:
      event_report_file_names = None

    file_paths_to_exclude = set()

    for video_file_path in video_file_paths:
      video_file_name = path.splitext(path.split(video_file_path)[1])[0]
      if (event_report_file_names and video_file_name 
      in event_report_file_names) \
          or (inference_report_file_names and video_file_name 
          in inference_report_file_names):
        file_paths_to_exclude.add(video_file_path)

    video_file_paths -= file_paths_to_exclude

  if args.ionodenamesfilepath is None \
      or not path.isfile(args.ionodenamesfilepath):
    io_node_names_path = path.join(models_dir_path, 'io_node_names.txt')
  else:
    io_node_names_path = args.ionodenamesfilepath
  logging.debug('io tensors path set to: {}'.format(io_node_names_path))

  node_name_map = IO.read_node_names(io_node_names_path)

  if args.classnamesfilepath is None \
      or not path.isfile(args.classnamesfilepath):
    class_names_path = path.join(models_root_dir_path, 'class_names.txt')
  else:
    class_names_path = args.classnamesfilepath
  logging.debug('labels path set to: {}'.format(class_names_path))

  if args.cpuonly:
    device_id_list = ['0']
    device_type = 'cpu'
  else:
    device_id_list = IO.get_device_ids()
    device_type = 'gpu'

  physical_device_count = len(device_id_list)

  logging.info('Found {} physical {} device(s).'.format(
    physical_device_count, device_type))

  valid_num_processes_list = get_valid_num_processes_per_device(device_type)

  if args.numprocessesperdevice not in valid_num_processes_list:
      raise ValueError(
        'The the number of processes to assign to each {} device is expected '
        'to be in the set {}.'.format(device_type, valid_num_processes_list))

  for i in range(physical_device_count,
                 physical_device_count * args.numprocessesperdevice):
    device_id_list.append(str(i))

  logical_device_count = len(device_id_list)

  logging.info('Generated an additional {} logical {} device(s).'.format(
    logical_device_count - physical_device_count, device_type))

  # child processes will dequeue and enqueue device names
  device_id_queue = Queue(logical_device_count)

  for device_id in device_id_list:
    device_id_queue.put(device_id)

  class_name_map = IO.read_class_names(class_names_path)

  logging.debug('loading model at path: {}'.format(model_file_path))

  return_code_queue_map = {}
  child_logger_thread_map = {}
  child_process_map = {}

  total_num_video_to_process = len(video_file_paths)

  total_num_processed_videos = 0
  total_num_processed_frames = 0
  total_analysis_duration = 0

  logging.info('Processing {} videos using {}'.format(
    total_num_video_to_process, args.modelname))

  def start_video_processor(video_file_path):
    # Before popping the next video off of the list and creating a process to
    # scan it, check to see if fewer than logical_device_count + 1 processes are
    # active. If not, Wait for a child process to release its semaphore
    # acquisition. If so, acquire the semaphore, pop the next video name,
    # create the next child process, and pass the semaphore to it
    video_dir_path, video_file_name = path.split(video_file_path)

    return_code_queue = Queue()

    return_code_queue_map[video_file_name] = return_code_queue

    logging.debug('creating new child process.')

    child_log_queue = Queue()

    child_logger_thread = Thread(target=child_logger_fn,
                                 args=(log_queue, child_log_queue))

    child_logger_thread.start()

    child_logger_thread_map[video_file_name] = child_logger_thread

    gpu_memory_fraction = args.gpumemoryfraction / args.numprocessesperdevice

    child_process = Process(
      target=process_video, name=path.splitext(video_file_name)[0],
      args=(video_file_path, output_dir_path, class_name_map, model_input_size,
            device_id_queue, return_code_queue, child_log_queue, log_level,
            device_type, logical_device_count, physical_device_count,
            ffmpeg_path, ffprobe_path, model_file_path, node_name_map,
            gpu_memory_fraction, args.crop, args.cropwidth, args.cropheight,
            args.cropx, args.cropy, args.extracttimestamps,
            args.timestampmaxwidth, args.timestampheight, args.timestampx,
            args.timestampy, args.deinterlace, args.numchannels, args.batchsize,
            args.smoothprobs, args.smoothingfactor, args.binarizeprobs))

    logging.debug('starting child process.')

    child_process.start()

    child_process_map[video_file_name] = child_process

  def close_completed_video_processors(
      total_num_processed_videos, total_num_processed_frames,
      total_analysis_duration):
    for video_file_name in list(return_code_queue_map.keys()):
      return_code_queue = return_code_queue_map[video_file_name]

      try:
        return_code_map = return_code_queue.get_nowait()

        return_code = return_code_map['return_code']
        return_value = return_code_map['return_value']

        child_process = child_process_map[video_file_name]

        logging.debug(
          'child process {} returned with exit code {} and exit value '
          '{}'.format(child_process.pid, return_code, return_value))

        if return_code == 'success':
          total_num_processed_videos += 1
          total_num_processed_frames += return_value
          total_analysis_duration += return_code_map['analysis_duration']

        child_logger_thread = child_logger_thread_map[video_file_name]
        
        logging.debug('joining logger thread for child process {}'.format(
          child_process.pid))

        child_logger_thread.join(timeout=15)

        if child_logger_thread.is_alive():
          logging.warning(
            'logger thread for child process {} remained alive following join '
            'timeout'.format(child_process.pid))
        
        logging.debug('joining child process {}'.format(child_process.pid))
        
        child_process.join(timeout=15)

        # if the child process has not yet terminated, kill the child process at
        # the risk of losing any log message not yet buffered by the main logger
        try:
          os.kill(child_process.pid, signal.SIGKILL)
          logging.warning(
            'child process {} remained alive following join timeout and had to '
            'be killed'.format(child_process.pid))
        except:
          pass
        
        return_code_queue.close()
        
        return_code_queue_map.pop(video_file_name)
        child_logger_thread_map.pop(video_file_name)
        child_process_map.pop(video_file_name)
      except Empty:
        pass

    return total_num_processed_videos, total_num_processed_frames, \
           total_analysis_duration

  start = time()

  while len(video_file_paths) > 0:
    # block if logical_device_count + 1 child processes are active
    while len(return_code_queue_map) > logical_device_count:
      total_num_processed_videos, total_num_processed_frames, \
      total_analysis_duration = close_completed_video_processors(
        total_num_processed_videos, total_num_processed_frames,
        total_analysis_duration)

    try:
      _ = main_interrupt_queue.get_nowait()
      logging.debug(
        'breaking out of child process generation following interrupt signal')
      break
    except:
      pass

    video_file_path = video_file_paths.pop()

    try:
      start_video_processor(video_file_path)
    except Exception as e:
      logging.error('an unknown error has occured while processing '
                    '{}'.format(video_file_path))
      logging.error(e)

  while len(return_code_queue_map) > 0:
    logging.debug('waiting for the final {} child processes to '
                  'terminate'.format(len(return_code_queue_map)))

    total_num_processed_videos, total_num_processed_frames, \
    total_analysis_duration = close_completed_video_processors(
      total_num_processed_videos, total_num_processed_frames,
      total_analysis_duration)

    # by now, the last device_id_queue_len videos are being processed,
    # so we can afford to poll for their completion infrequently
    if len(return_code_queue_map) > 0:
      sleep_duration = 10
      logging.debug('sleeping for {} seconds'.format(sleep_duration))
      sleep(sleep_duration)

  end = time() - start

  processing_duration = IO.get_processing_duration(
    end, 'snva {} processed a total of {} videos and {} frames in:'.format(
      snva_version_string, total_num_processed_videos,
      total_num_processed_frames))
  logging.info(processing_duration)

  logging.info('Video analysis alone spanned a cumulative {:.02f} '
               'seconds'.format(total_analysis_duration))

  logging.info('exiting snva {} main process'.format(snva_version_string))