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# This file is part of audioread.
# Copyright 2013, Adrian Sampson.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
"""Decode audio files."""
from . import ffdec
from .exceptions import DecodeError, NoBackendError
from .version import version as __version__ # noqa
from .base import AudioFile # noqa
def _gst_available():
"""Determine whether Gstreamer and the Python GObject bindings are
installed.
"""
try:
import gi
except ImportError:
return False
try:
gi.require_version('Gst', '1.0')
except (ValueError, AttributeError):
return False
try:
from gi.repository import Gst # noqa
except ImportError:
return False
return True
def _ca_available():
"""Determines whether CoreAudio is available (i.e., we're running on
Mac OS X).
"""
import ctypes.util
lib = ctypes.util.find_library('AudioToolbox')
return lib is not None
def _mad_available():
"""Determines whether the pymad bindings are available."""
try:
import mad # noqa
except ImportError:
return False
else:
return True
# A cache for the available backends.
BACKENDS = []
def available_backends(flush_cache=False):
"""Returns a list of backends that are available on this system.
The list of backends is cached after the first call.
If the parameter `flush_cache` is set to `True`, then the cache
will be flushed and the backend list will be reconstructed.
"""
if BACKENDS and not flush_cache:
return BACKENDS
# Standard-library WAV and AIFF readers.
from . import rawread
result = [rawread.RawAudioFile]
# Core Audio.
if _ca_available():
from . import macca
result.append(macca.ExtAudioFile)
# GStreamer.
if _gst_available():
from . import gstdec
result.append(gstdec.GstAudioFile)
# MAD.
if _mad_available():
from . import maddec
result.append(maddec.MadAudioFile)
# FFmpeg.
if ffdec.available():
result.append(ffdec.FFmpegAudioFile)
# Cache the backends we found
BACKENDS[:] = result
return BACKENDS
def audio_open(path, backends=None):
"""Open an audio file using a library that is available on this
system.
The optional `backends` parameter can be a list of audio file
classes to try opening the file with. If it is not provided,
`audio_open` tries all available backends. If you call this function
many times, you can avoid the cost of checking for available
backends every time by calling `available_backends` once and passing
the result to each `audio_open` call.
If all backends fail to read the file, a NoBackendError exception is
raised.
"""
if backends is None:
backends = available_backends()
for BackendClass in backends:
try:
return BackendClass(path)
except DecodeError:
pass
# All backends failed!
raise NoBackendError()
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