+               pref = locale.getpreferredencoding()
+               # Mac OSX systems have this problem sometimes
+               if pref == '':
+                       return 'UTF-8'
+               return pref
+       except:
+               sys.stderr.write('WARNING: problem obtaining preferred encoding. Falling back to UTF-8.\n')
+               return 'UTF-8'
+
+class DownloadError(Exception):
+       """Download Error exception.
+       
+       This exception may be thrown by FileDownloader objects if they are not
+       configured to continue on errors. They will contain the appropriate
+       error message.
+       """
+       pass
+
+class SameFileError(Exception):
+       """Same File exception.
+
+       This exception will be thrown by FileDownloader objects if they detect
+       multiple files would have to be downloaded to the same file on disk.
+       """
+       pass
+
+class PostProcessingError(Exception):
+       """Post Processing exception.
+
+       This exception may be raised by PostProcessor's .run() method to
+       indicate an error in the postprocessing task.
+       """
+       pass
+
+class UnavailableFormatError(Exception):
+       """Unavailable Format exception.
+
+       This exception will be thrown when a video is requested
+       in a format that is not available for that video.
+       """
+       pass
+
+class ContentTooShortError(Exception):
+       """Content Too Short exception.
+
+       This exception may be raised by FileDownloader objects when a file they
+       download is too small for what the server announced first, indicating
+       the connection was probably interrupted.
+       """
+       # Both in bytes
+       downloaded = None
+       expected = None
+
+       def __init__(self, downloaded, expected):
+               self.downloaded = downloaded
+               self.expected = expected
+
+class FileDownloader(object):
+       """File Downloader class.
+
+       File downloader objects are the ones responsible of downloading the
+       actual video file and writing it to disk if the user has requested
+       it, among some other tasks. In most cases there should be one per
+       program. As, given a video URL, the downloader doesn't know how to
+       extract all the needed information, task that InfoExtractors do, it
+       has to pass the URL to one of them.
+
+       For this, file downloader objects have a method that allows
+       InfoExtractors to be registered in a given order. When it is passed
+       a URL, the file downloader handles it to the first InfoExtractor it
+       finds that reports being able to handle it. The InfoExtractor extracts
+       all the information about the video or videos the URL refers to, and
+       asks the FileDownloader to process the video information, possibly
+       downloading the video.
+
+       File downloaders accept a lot of parameters. In order not to saturate
+       the object constructor with arguments, it receives a dictionary of
+       options instead. These options are available through the params
+       attribute for the InfoExtractors to use. The FileDownloader also
+       registers itself as the downloader in charge for the InfoExtractors
+       that are added to it, so this is a "mutual registration".
+
+       Available options:
+
+       username:       Username for authentication purposes.
+       password:       Password for authentication purposes.
+       usenetrc:       Use netrc for authentication instead.
+       quiet:          Do not print messages to stdout.
+       forceurl:       Force printing final URL.
+       forcetitle:     Force printing title.
+       simulate:       Do not download the video files.
+       format:         Video format code.
+       outtmpl:        Template for output names.
+       ignoreerrors:   Do not stop on download errors.
+       ratelimit:      Download speed limit, in bytes/sec.
+       nooverwrites:   Prevent overwriting files.
+       continuedl:     Try to continue downloads if possible.
+       """
+
+       params = None
+       _ies = []
+       _pps = []
+       _download_retcode = None
+
+       def __init__(self, params):
+               """Create a FileDownloader object with the given options."""
+               self._ies = []
+               self._pps = []
+               self._download_retcode = 0
+               self.params = params
+       
+       @staticmethod
+       def pmkdir(filename):
+               """Create directory components in filename. Similar to Unix "mkdir -p"."""
+               components = filename.split(os.sep)
+               aggregate = [os.sep.join(components[0:x]) for x in xrange(1, len(components))]
+               aggregate = ['%s%s' % (x, os.sep) for x in aggregate] # Finish names with separator
+               for dir in aggregate:
+                       if not os.path.exists(dir):
+                               os.mkdir(dir)
+       
+       @staticmethod
+       def format_bytes(bytes):
+               if bytes is None:
+                       return 'N/A'
+               if type(bytes) is str:
+                       bytes = float(bytes)
+               if bytes == 0.0:
+                       exponent = 0
+               else:
+                       exponent = long(math.log(bytes, 1024.0))
+               suffix = 'bkMGTPEZY'[exponent]
+               converted = float(bytes) / float(1024**exponent)
+               return '%.2f%s' % (converted, suffix)
+
+       @staticmethod
+       def calc_percent(byte_counter, data_len):
+               if data_len is None:
+                       return '---.-%'
+               return '%6s' % ('%3.1f%%' % (float(byte_counter) / float(data_len) * 100.0))
+
+       @staticmethod
+       def calc_eta(start, now, total, current):
+               if total is None:
+                       return '--:--'
+               dif = now - start
+               if current == 0 or dif < 0.001: # One millisecond
+                       return '--:--'
+               rate = float(current) / dif
+               eta = long((float(total) - float(current)) / rate)
+               (eta_mins, eta_secs) = divmod(eta, 60)
+               if eta_mins > 99:
+                       return '--:--'
+               return '%02d:%02d' % (eta_mins, eta_secs)
+
+       @staticmethod
+       def calc_speed(start, now, bytes):
+               dif = now - start
+               if bytes == 0 or dif < 0.001: # One millisecond
+                       return '%10s' % '---b/s'
+               return '%10s' % ('%s/s' % FileDownloader.format_bytes(float(bytes) / dif))
+
+       @staticmethod
+       def best_block_size(elapsed_time, bytes):
+               new_min = max(bytes / 2.0, 1.0)
+               new_max = min(max(bytes * 2.0, 1.0), 4194304) # Do not surpass 4 MB
+               if elapsed_time < 0.001:
+                       return long(new_max)
+               rate = bytes / elapsed_time
+               if rate > new_max:
+                       return long(new_max)
+               if rate < new_min:
+                       return long(new_min)
+               return long(rate)
+
+       @staticmethod
+       def parse_bytes(bytestr):
+               """Parse a string indicating a byte quantity into a long integer."""
+               matchobj = re.match(r'(?i)^(\d+(?:\.\d+)?)([kMGTPEZY]?)$', bytestr)
+               if matchobj is None:
+                       return None
+               number = float(matchobj.group(1))
+               multiplier = 1024.0 ** 'bkmgtpezy'.index(matchobj.group(2).lower())
+               return long(round(number * multiplier))
+
+       @staticmethod
+       def verify_url(url):
+               """Verify a URL is valid and data could be downloaded. Return real data URL."""
+               request = urllib2.Request(url, None, std_headers)
+               data = urllib2.urlopen(request)
+               data.read(1)
+               url = data.geturl()
+               data.close()
+               return url
+
+       def add_info_extractor(self, ie):
+               """Add an InfoExtractor object to the end of the list."""
+               self._ies.append(ie)
+               ie.set_downloader(self)
+       
+       def add_post_processor(self, pp):
+               """Add a PostProcessor object to the end of the chain."""
+               self._pps.append(pp)
+               pp.set_downloader(self)
+       
+       def to_stdout(self, message, skip_eol=False):
+               """Print message to stdout if not in quiet mode."""
+               if not self.params.get('quiet', False):
+                       print (u'%s%s' % (message, [u'\n', u''][skip_eol])).encode(preferredencoding()),
+                       sys.stdout.flush()
+       
+       def to_stderr(self, message):
+               """Print message to stderr."""
+               print >>sys.stderr, message.encode(preferredencoding())
+       
+       def fixed_template(self):
+               """Checks if the output template is fixed."""
+               return (re.search(ur'(?u)%\(.+?\)s', self.params['outtmpl']) is None)
+
+       def trouble(self, message=None):
+               """Determine action to take when a download problem appears.
+
+               Depending on if the downloader has been configured to ignore
+               download errors or not, this method may throw an exception or
+               not when errors are found, after printing the message.
+               """
+               if message is not None:
+                       self.to_stderr(message)
+               if not self.params.get('ignoreerrors', False):
+                       raise DownloadError(message)
+               self._download_retcode = 1
+
+       def slow_down(self, start_time, byte_counter):
+               """Sleep if the download speed is over the rate limit."""
+               rate_limit = self.params.get('ratelimit', None)
+               if rate_limit is None or byte_counter == 0:
+                       return
+               now = time.time()
+               elapsed = now - start_time
+               if elapsed <= 0.0:
+                       return
+               speed = float(byte_counter) / elapsed
+               if speed > rate_limit:
+                       time.sleep((byte_counter - rate_limit * (now - start_time)) / rate_limit)
+
+       def report_destination(self, filename):
+               """Report destination filename."""
+               self.to_stdout(u'[download] Destination: %s' % filename)
+       
+       def report_progress(self, percent_str, data_len_str, speed_str, eta_str):
+               """Report download progress."""
+               self.to_stdout(u'\r[download] %s of %s at %s ETA %s' %
+                               (percent_str, data_len_str, speed_str, eta_str), skip_eol=True)
+
+       def report_resuming_byte(self, resume_len):
+               """Report attemtp to resume at given byte."""
+               self.to_stdout(u'[download] Resuming download at byte %s' % resume_len)
+       
+       def report_file_already_downloaded(self, file_name):
+               """Report file has already been fully downloaded."""
+               self.to_stdout(u'[download] %s has already been downloaded' % file_name)
+       
+       def report_unable_to_resume(self):
+               """Report it was impossible to resume download."""
+               self.to_stdout(u'[download] Unable to resume')
+       
+       def report_finish(self):
+               """Report download finished."""
+               self.to_stdout(u'')
+
+       def process_info(self, info_dict):
+               """Process a single dictionary returned by an InfoExtractor."""
+               # Do nothing else if in simulate mode
+               if self.params.get('simulate', False):
+                       try:
+                               info_dict['url'] = self.verify_url(info_dict['url'])
+                       except (OSError, IOError, urllib2.URLError, httplib.HTTPException, socket.error), err:
+                               raise UnavailableFormatError
+
+                       # Forced printings
+                       if self.params.get('forcetitle', False):
+                               print info_dict['title'].encode(preferredencoding())
+                       if self.params.get('forceurl', False):
+                               print info_dict['url'].encode(preferredencoding())
+
+                       return
+                       
+               try:
+                       template_dict = dict(info_dict)
+                       template_dict['epoch'] = unicode(long(time.time()))
+                       filename = self.params['outtmpl'] % template_dict
+               except (ValueError, KeyError), err:
+                       self.trouble('ERROR: invalid output template or system charset: %s' % str(err))
+               if self.params['nooverwrites'] and os.path.exists(filename):
+                       self.to_stderr(u'WARNING: file exists: %s; skipping' % filename)
+                       return
+
+               try:
+                       self.pmkdir(filename)
+               except (OSError, IOError), err:
+                       self.trouble('ERROR: unable to create directories: %s' % str(err))
+                       return
+
+               try:
+                       success = self._do_download(filename, info_dict['url'])
+               except (OSError, IOError), err:
+                       raise UnavailableFormatError
+               except (urllib2.URLError, httplib.HTTPException, socket.error), err:
+                       self.trouble('ERROR: unable to download video data: %s' % str(err))
+                       return
+               except (ContentTooShortError, ), err:
+                       self.trouble('ERROR: content too short (expected %s bytes and served %s)' % (err.expected, err.downloaded))
+                       return
+
+               if success:
+                       try:
+                               self.post_process(filename, info_dict)
+                       except (PostProcessingError), err:
+                               self.trouble('ERROR: postprocessing: %s' % str(err))
+                               return
+
+       def download(self, url_list):
+               """Download a given list of URLs."""
+               if len(url_list) > 1 and self.fixed_template():
+                       raise SameFileError(self.params['outtmpl'])
+
+               for url in url_list:
+                       suitable_found = False
+                       for ie in self._ies:
+                               # Go to next InfoExtractor if not suitable
+                               if not ie.suitable(url):
+                                       continue
+
+                               # Suitable InfoExtractor found
+                               suitable_found = True
+
+                               # Extract information from URL and process it
+                               ie.extract(url)
+
+                               # Suitable InfoExtractor had been found; go to next URL
+                               break
+
+                       if not suitable_found:
+                               self.trouble('ERROR: no suitable InfoExtractor: %s' % url)
+
+               return self._download_retcode
+
+       def post_process(self, filename, ie_info):
+               """Run the postprocessing chain on the given file."""
+               info = dict(ie_info)
+               info['filepath'] = filename
+               for pp in self._pps:
+                       info = pp.run(info)
+                       if info is None:
+                               break
+       
+       def _do_download(self, filename, url):
+               stream = None
+               open_mode = 'ab'
+
+               basic_request = urllib2.Request(url, None, std_headers)
+               request = urllib2.Request(url, None, std_headers)
+
+               # Attempt to resume download with "continuedl" option
+               if os.path.isfile(filename):
+                       resume_len = os.path.getsize(filename)
+               else:
+                       resume_len = 0
+               if self.params['continuedl'] and resume_len != 0:
+                       self.report_resuming_byte(resume_len)
+                       request.add_header('Range','bytes=%d-' % resume_len)
+
+               # Establish connection
+               try:
+                       data = urllib2.urlopen(request)
+               except (urllib2.HTTPError, ), err:
+                       if err.code != 416: #  416 is 'Requested range not satisfiable'
+                               raise
+                       data = urllib2.urlopen(basic_request)
+                       content_length = data.info()['Content-Length']
+                       if content_length is not None and long(content_length) == resume_len:
+                               self.report_file_already_downloaded(filename)
+                               return True
+                       else:
+                               self.report_unable_to_resume()
+                               open_mode = 'wb'
+
+               data_len = data.info().get('Content-length', None)
+               data_len_str = self.format_bytes(data_len)
+               byte_counter = 0
+               block_size = 1024
+               start = time.time()
+               while True:
+                       # Download and write
+                       before = time.time()
+                       data_block = data.read(block_size)
+                       after = time.time()
+                       data_block_len = len(data_block)
+                       if data_block_len == 0:
+                               break
+                       byte_counter += data_block_len
+
+                       # Open file just in time
+                       if stream is None:
+                               try:
+                                       stream = open(filename, open_mode)
+                                       self.report_destination(filename)
+                               except (OSError, IOError), err:
+                                       self.trouble('ERROR: unable to open for writing: %s' % str(err))
+                                       return False
+                       stream.write(data_block)
+                       block_size = self.best_block_size(after - before, data_block_len)
+
+                       # Progress message
+                       percent_str = self.calc_percent(byte_counter, data_len)
+                       eta_str = self.calc_eta(start, time.time(), data_len, byte_counter)
+                       speed_str = self.calc_speed(start, time.time(), byte_counter)
+                       self.report_progress(percent_str, data_len_str, speed_str, eta_str)
+
+                       # Apply rate limit
+                       self.slow_down(start, byte_counter)
+
+               self.report_finish()
+               if data_len is not None and str(byte_counter) != data_len:
+                       raise ContentTooShortError(byte_counter, long(data_len))
+               return True
+
+class InfoExtractor(object):
+       """Information Extractor class.
+
+       Information extractors are the classes that, given a URL, extract
+       information from the video (or videos) the URL refers to. This
+       information includes the real video URL, the video title and simplified
+       title, author and others. The information is stored in a dictionary
+       which is then passed to the FileDownloader. The FileDownloader
+       processes this information possibly downloading the video to the file
+       system, among other possible outcomes. The dictionaries must include
+       the following fields:
+
+       id:             Video identifier.
+       url:            Final video URL.
+       uploader:       Nickname of the video uploader.
+       title:          Literal title.
+       stitle:         Simplified title.
+       ext:            Video filename extension.
+
+       Subclasses of this one should re-define the _real_initialize() and
+       _real_extract() methods, as well as the suitable() static method.
+       Probably, they should also be instantiated and added to the main
+       downloader.
+       """
+
+       _ready = False
+       _downloader = None
+
+       def __init__(self, downloader=None):
+               """Constructor. Receives an optional downloader."""
+               self._ready = False
+               self.set_downloader(downloader)
+
+       @staticmethod
+       def suitable(url):
+               """Receives a URL and returns True if suitable for this IE."""
+               return False
+
+       def initialize(self):
+               """Initializes an instance (authentication, etc)."""
+               if not self._ready:
+                       self._real_initialize()
+                       self._ready = True
+
+       def extract(self, url):
+               """Extracts URL information and returns it in list of dicts."""
+               self.initialize()
+               return self._real_extract(url)
+
+       def set_downloader(self, downloader):
+               """Sets the downloader for this IE."""
+               self._downloader = downloader
+       
+       def _real_initialize(self):
+               """Real initialization process. Redefine in subclasses."""
+               pass
+
+       def _real_extract(self, url):
+               """Real extraction process. Redefine in subclasses."""
+               pass
+
+class YoutubeIE(InfoExtractor):
+       """Information extractor for youtube.com."""
+
+       _VALID_URL = r'^((?:http://)?(?:\w+\.)?youtube\.com/(?:(?:v/)|(?:(?:watch(?:\.php)?)?\?(?:.+&)?v=)))?([0-9A-Za-z_-]+)(?(1).+)?$'
+       _LANG_URL = r'http://uk.youtube.com/?hl=en&persist_hl=1&gl=US&persist_gl=1&opt_out_ackd=1'
+       _LOGIN_URL = 'http://www.youtube.com/signup?next=/&gl=US&hl=en'
+       _AGE_URL = 'http://www.youtube.com/verify_age?next_url=/&gl=US&hl=en'
+       _NETRC_MACHINE = 'youtube'
+       _available_formats = ['22', '35', '18', '5', '17', '13', None] # listed in order of priority for -b flag
+       _video_extensions = {
+               '13': '3gp',
+               '17': 'mp4',
+               '18': 'mp4',
+               '22': 'mp4',
+       }
+
+       @staticmethod
+       def suitable(url):
+               return (re.match(YoutubeIE._VALID_URL, url) is not None)
+
+       @staticmethod
+       def htmlentity_transform(matchobj):
+               """Transforms an HTML entity to a Unicode character."""
+               entity = matchobj.group(1)
+
+               # Known non-numeric HTML entity
+               if entity in htmlentitydefs.name2codepoint:
+                       return unichr(htmlentitydefs.name2codepoint[entity])
+
+               # Unicode character
+               mobj = re.match(ur'(?u)#(x?\d+)', entity)
+               if mobj is not None:
+                       numstr = mobj.group(1)
+                       if numstr.startswith(u'x'):
+                               base = 16
+                               numstr = u'0%s' % numstr
+                       else:
+                               base = 10
+                       return unichr(long(numstr, base))
+
+               # Unknown entity in name, return its literal representation
+               return (u'&%s;' % entity)
+
+       def report_lang(self):
+               """Report attempt to set language."""
+               self._downloader.to_stdout(u'[youtube] Setting language')
+
+       def report_login(self):
+               """Report attempt to log in."""
+               self._downloader.to_stdout(u'[youtube] Logging in')
+       
+       def report_age_confirmation(self):
+               """Report attempt to confirm age."""
+               self._downloader.to_stdout(u'[youtube] Confirming age')
+       
+       def report_video_info_webpage_download(self, video_id):
+               """Report attempt to download video info webpage."""
+               self._downloader.to_stdout(u'[youtube] %s: Downloading video info webpage' % video_id)
+       
+       def report_information_extraction(self, video_id):
+               """Report attempt to extract video information."""
+               self._downloader.to_stdout(u'[youtube] %s: Extracting video information' % video_id)
+       
+       def report_unavailable_format(self, video_id, format):
+               """Report extracted video URL."""
+               self._downloader.to_stdout(u'[youtube] %s: Format %s not available' % (video_id, format))
+       
+       def _real_initialize(self):
+               if self._downloader is None:
+                       return
+
+               username = None
+               password = None
+               downloader_params = self._downloader.params
+
+               # Attempt to use provided username and password or .netrc data
+               if downloader_params.get('username', None) is not None:
+                       username = downloader_params['username']
+                       password = downloader_params['password']
+               elif downloader_params.get('usenetrc', False):
+                       try:
+                               info = netrc.netrc().authenticators(self._NETRC_MACHINE)
+                               if info is not None:
+                                       username = info[0]
+                                       password = info[2]
+                               else:
+                                       raise netrc.NetrcParseError('No authenticators for %s' % self._NETRC_MACHINE)
+                       except (IOError, netrc.NetrcParseError), err:
+                               self._downloader.to_stderr(u'WARNING: parsing .netrc: %s' % str(err))
+                               return
+
+               # Set language
+               request = urllib2.Request(self._LANG_URL, None, std_headers)
+               try:
+                       self.report_lang()
+                       urllib2.urlopen(request).read()
+               except (urllib2.URLError, httplib.HTTPException, socket.error), err:
+                       self._downloader.to_stderr(u'WARNING: unable to set language: %s' % str(err))
+                       return
+
+               # No authentication to be performed
+               if username is None:
+                       return
+