text: from __future__ import division
  
  import json
  import os
  import re
  import sys
  from contextlib import contextmanager
  from errno import ENOENT
  from subprocess import Popen, PIPE
  from math import log, ceil
  from tempfile import TemporaryFile
  from warnings import warn
  from functools import wraps
  
  from .exceptions import MissingConverter
  
  try:
      import audioop
  except ImportError:
      import pyaudioop as audioop
  
  if sys.version_info >= (3, 0):
      basestring = str
  
  FRAME_WIDTHS = {
      8: 1,
      16: 2,
      32: 4,
  }
  ARRAY_TYPES = {
      8: "b",
      16: "h",
      32: "i",
  }
  ARRAY_RANGES = {
      8: (-0x80, 0x7f),
      16: (-0x8000, 0x7fff),
      32: (-0x80000000, 0x7fffffff),
  }
  
  
  def get_frame_width(bit_depth):
      return FRAME_WIDTHS[bit_depth]
  
  
  def get_array_type(bit_depth, signed=True):
      t = ARRAY_TYPES[bit_depth]
      if not signed:
          t = t.upper()
      return t
  
  
  def get_min_max_value(bit_depth):
      return ARRAY_RANGES[bit_depth]
  
  
  def _fd_or_path_or_tempfile(fd, mode='w+b', tempfile=True):
      close_fd = False
      if fd is None and tempfile:
          fd = TemporaryFile(mode=mode)
          close_fd = True
  
      if isinstance(fd, basestring):
          fd = open(fd, mode=mode)
          close_fd = True
  
      try:
          if isinstance(fd, os.PathLike):
              fd = open(fd, mode=mode)
              close_fd = True
      except AttributeError:
          # module os has no attribute PathLike, so we're on python < 3.6.
          # The protocol we're trying to support doesn't exist, so just pass.
          pass
  
      return fd, close_fd
  
  
  def db_to_float(db, using_amplitude=True):
      """
      Converts the input db to a float, which represents the equivalent
      ratio in power.
      """
      db = float(db)
      if using_amplitude:
          return 10 ** (db / 20)
      else:  # using power
          return 10 ** (db / 10)
  
  
  def ratio_to_db(ratio, val2=None, using_amplitude=True):
      """
      Converts the input float to db, which represents the equivalent
      to the ratio in power represented by the multiplier passed in.
      """
      ratio = float(ratio)
  
      # accept 2 values and use the ratio of val1 to val2
      if val2 is not None:
          ratio = ratio / val2
  
      # special case for multiply-by-zero (convert to silence)
      if ratio == 0:
          return -float('inf')
  
      if using_amplitude:
          return 20 * log(ratio, 10)
      else:  # using power
          return 10 * log(ratio, 10)
  
  
  def register_pydub_effect(fn, name=None):
      """
      decorator for adding pydub effects to the AudioSegment objects.
      example use:
          @register_pydub_effect
          def normalize(audio_segment):
              ...
      or you can specify a name:
          @register_pydub_effect("normalize")
          def normalize_audio_segment(audio_segment):
              ...
      """
      if isinstance(fn, basestring):
          name = fn
          return lambda fn: register_pydub_effect(fn, name)
  
      if name is None:
          name = fn.__name__
  
      from .audio_segment import AudioSegment
      setattr(AudioSegment, name, fn)
      return fn
  
  
  def make_chunks(audio_segment, chunk_length):
      """
      Breaks an AudioSegment into chunks that are <chunk_length> milliseconds
      long.
      if chunk_length is 50 then you'll get a list of 50 millisecond long audio
      segments back (except the last one, which can be shorter)
      """
      number_of_chunks = ceil(len(audio_segment) / float(chunk_length))
      return [audio_segment[i * chunk_length:(i + 1) * chunk_length]
              for i in range(int(number_of_chunks))]
  
  
  def which(program):
      """
      Mimics behavior of UNIX which command.
      """
      # Add .exe program extension for windows support
      if os.name == "nt" and not program.endswith(".exe"):
          program += ".exe"
  
      envdir_list = [os.curdir] + os.environ["PATH"].split(os.pathsep)
  
      for envdir in envdir_list:
          program_path = os.path.join(envdir, program)
          if os.path.isfile(program_path) and os.access(program_path, os.X_OK):
              return program_path
  
  
  @contextmanager
  def try_run_executable():
      """Handle exception for missing application.
  
      raises:
          MissingConverter: Prompt user to install missing dependency.
      """
      try:
          yield
      except EnvironmentError as e:
          if e.errno == ENOENT:
              message = "{0}\n\n{1}\n".format(
                  str(sys.exc_info()),
                  "Check if ffmpeg or avlib are installed."
              )
              raise MissingConverter(message)
  
  
  def get_encoder_name():
      """
      Return enconder default application for system, either avconv or ffmpeg
      """
      if which("avconv"):
          return "avconv"
      elif which("ffmpeg"):
          return "ffmpeg"
      else:
          warn("Couldn't find ffmpeg or avconv - defaulting to ffmpeg, but may not work", RuntimeWarning)
          return "ffmpeg"
  
  
  def get_player_name():
      """
      Return enconder default application for system, either avconv or ffmpeg
      """
      if which("avplay"):
          return "avplay"
      elif which("ffplay"):
          return "ffplay"
      else:
          warn("Couldn't find ffplay or avplay - defaulting to ffplay, but may not work", RuntimeWarning)
          return "ffplay"
  
  
  def get_prober_name():
      """
      Return probe application, either avconv or ffmpeg
      """
      if which("avprobe"):
          return "avprobe"
      elif which("ffprobe"):
          return "ffprobe"
      else:
          warn("Couldn't find ffprobe or avprobe - defaulting to ffprobe, but may not work", RuntimeWarning)
          return "ffprobe"
  
  
  def fsdecode(filename):
      """Wrapper for os.fsdecode which was introduced in python 3.2 ."""
  
      if sys.version_info >= (3, 2):
          PathLikeTypes = (basestring, bytes)
          if sys.version_info >= (3, 6):
              PathLikeTypes += (os.PathLike,)
          if isinstance(filename, PathLikeTypes):
              return os.fsdecode(filename)
      else:
          if isinstance(filename, bytes):
              return filename.decode(sys.getfilesystemencoding())
          if isinstance(filename, basestring):
              return filename
  
      raise TypeError("type {0} not accepted by fsdecode".format(type(filename)))
  
  
  def get_extra_info(stderr):
      """
      avprobe sometimes gives more information on stderr than
      on the json output. The information has to be extracted
      from stderr of the format of:
      '    Stream #0:0: Audio: flac, 88200 Hz, stereo, s32 (24 bit)'
      or (macOS version):
      '    Stream #0:0: Audio: vorbis'
      '      44100 Hz, stereo, fltp, 320 kb/s'
  
      :type stderr: str
      :rtype: list of dict
      """
      extra_info = {}
  
      re_stream = r'(?P<space_start> +)Stream #0[:\.](?P<stream_id>([0-9]+))(?P<content_0>.+)\n?(?! *Stream)((?P<space_end> +)(?P<content_1>.+))?'
      for i in re.finditer(re_stream, stderr):
          if i.group('space_end') is not None and len(i.group('space_start')) <= len(
                  i.group('space_end')):
              content_line = ','.join([i.group('content_0'), i.group('content_1')])
          else:
              content_line = i.group('content_0')
          tokens = [x.strip() for x in re.split('[:,]', content_line) if x]
          extra_info[int(i.group('stream_id'))] = tokens
      return extra_info
  
  
  def mediainfo_json(filepath, read_ahead_limit=-1):
      """Return json dictionary with media info(codec, duration, size, bitrate...) from filepath
      """
      prober = get_prober_name()
      command_args = [
          "-v", "info",
          "-show_format",
          "-show_streams",
      ]
      try:
          command_args += [fsdecode(filepath)]
          stdin_parameter = None
          stdin_data = None
      except TypeError:
          if prober == 'ffprobe':
              command_args += ["-read_ahead_limit", str(read_ahead_limit),
                               "cache:pipe:0"]
          else:
              command_args += ["-"]
          stdin_parameter = PIPE
          file, close_file = _fd_or_path_or_tempfile(filepath, 'rb', tempfile=False)
          file.seek(0)
          stdin_data = file.read()
          if close_file:
              file.close()
  
      command = [prober, '-of', 'json'] + command_args
      with try_run_executable():
          res = Popen(command, stdin=stdin_parameter, stdout=PIPE, stderr=PIPE)
      output, stderr = res.communicate(input=stdin_data)
      output = output.decode("utf-8", 'ignore')
      stderr = stderr.decode("utf-8", 'ignore')
  
      info = json.loads(output)
  
      if not info:
          # If ffprobe didn't give any information, just return it
          # (for example, because the file doesn't exist)
          return info
  
      extra_info = get_extra_info(stderr)
  
      audio_streams = [x for x in info['streams'] if x['codec_type'] == 'audio']
      if len(audio_streams) == 0:
          return info
  
      # We just operate on the first audio stream in case there are more
      stream = audio_streams[0]
  
      def set_property(stream, prop, value):
          if prop not in stream or stream[prop] == 0:
              stream[prop] = value
  
      for token in extra_info[stream['index']]:
          m = re.match('([su]([0-9]{1,2})p?) \(([0-9]{1,2}) bit\)$', token)
          m2 = re.match('([su]([0-9]{1,2})p?)( \(default\))?$', token)
          if m:
              set_property(stream, 'sample_fmt', m.group(1))
              set_property(stream, 'bits_per_sample', int(m.group(2)))
              set_property(stream, 'bits_per_raw_sample', int(m.group(3)))
          elif m2:
              set_property(stream, 'sample_fmt', m2.group(1))
              set_property(stream, 'bits_per_sample', int(m2.group(2)))
              set_property(stream, 'bits_per_raw_sample', int(m2.group(2)))
          elif re.match('(flt)p?( \(default\))?$', token):
              set_property(stream, 'sample_fmt', token)
              set_property(stream, 'bits_per_sample', 32)
              set_property(stream, 'bits_per_raw_sample', 32)
          elif re.match('(dbl)p?( \(default\))?$', token):
              set_property(stream, 'sample_fmt', token)
              set_property(stream, 'bits_per_sample', 64)
              set_property(stream, 'bits_per_raw_sample', 64)
      return info
  
  
  def mediainfo(filepath):
      """Return dictionary with media info(codec, duration, size, bitrate...) from filepath
      """
  
      prober = get_prober_name()
      command_args = [
          "-v", "quiet",
          "-show_format",
          "-show_streams",
          filepath
      ]
  
      command = [prober, '-of', 'old'] + command_args
      with try_run_executable():
          res = Popen(command, stdout=PIPE)
      output = res.communicate()[0].decode("utf-8")
  
      if res.returncode != 0:
          command = [prober] + command_args
          with try_run_executable():
              output = (
                  Popen(command, stdout=PIPE)
                  .communicate()[0]
                  .decode("utf-8")
              )
  
      rgx = re.compile(r"(?:(?P<inner_dict>.*?):)?(?P<key>.*?)\=(?P<value>.*?)$")
      info = {}
  
      if sys.platform == 'win32':
          output = output.replace("\r", "")
  
      for line in output.split("\n"):
          # print(line)
          mobj = rgx.match(line)
  
          if mobj:
              # print(mobj.groups())
              inner_dict, key, value = mobj.groups()
  
              if inner_dict:
                  try:
                      info[inner_dict]
                  except KeyError:
                      info[inner_dict] = {}
                  info[inner_dict][key] = value
              else:
                  info[key] = value
  
      return info
  
  
  def cache_codecs(function):
      cache = {}
  
      @wraps(function)
      def wrapper():
          try:
              return cache[0]
          except:
              cache[0] = function()
              return cache[0]
  
      return wrapper
  
  
  @cache_codecs
  def get_supported_codecs():
      encoder = get_encoder_name()
      command = [encoder, "-codecs"]
      with try_run_executable():
          res = Popen(command, stdout=PIPE, stderr=PIPE)
      output = res.communicate()[0].decode("utf-8")
      if res.returncode != 0:
          return []
  
      if sys.platform == 'win32':
          output = output.replace("\r", "")
  
  
      rgx = re.compile(r"^([D.][E.][AVS.][I.][L.][S.]) (\w*) +(.*)")
      decoders = set()
      encoders = set()
      for line in output.split('\n'):
          match = rgx.match(line.strip())
          if not match:
              continue
          flags, codec, name = match.groups()
  
          if flags[0] == 'D':
              decoders.add(codec)
  
          if flags[1] == 'E':
              encoders.add(codec)
  
      return (decoders, encoders)
  
  
  def get_supported_decoders():
      return get_supported_codecs()[0]
  
  
  def get_supported_encoders():
      return get_supported_codecs()[1]
  
  def stereo_to_ms(audio_segment):
  	'''
  	Left-Right -> Mid-Side
  	'''
  	channel = audio_segment.split_to_mono()
  	channel = [channel[0].overlay(channel[1]), channel[0].overlay(channel[1].invert_phase())]
  	return AudioSegment.from_mono_audiosegments(channel[0], channel[1])
  
  def ms_to_stereo(audio_segment):
  	'''
  	Mid-Side -> Left-Right
  	'''
  	channel = audio_segment.split_to_mono()
  	channel = [channel[0].overlay(channel[1]) - 3, channel[0].overlay(channel[1].invert_phase()) - 3]
  	return AudioSegment.from_mono_audiosegments(channel[0], channel[1])
  
  