349 lines
11 KiB
Python
349 lines
11 KiB
Python
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# This file is part of audioread.
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# Copyright 2011, Adrian Sampson.
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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"""Read audio files using CoreAudio on Mac OS X."""
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import copy
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import ctypes
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import ctypes.util
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import os
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import sys
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from .exceptions import DecodeError
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from .base import AudioFile
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# CoreFoundation and CoreAudio libraries along with their function
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# prototypes.
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def _load_framework(name):
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return ctypes.cdll.LoadLibrary(ctypes.util.find_library(name))
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_coreaudio = _load_framework('AudioToolbox')
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_corefoundation = _load_framework('CoreFoundation')
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# Convert CFStrings to C strings.
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_corefoundation.CFStringGetCStringPtr.restype = ctypes.c_char_p
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_corefoundation.CFStringGetCStringPtr.argtypes = [ctypes.c_void_p,
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ctypes.c_int]
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# Free memory.
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_corefoundation.CFRelease.argtypes = [ctypes.c_void_p]
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# Create a file:// URL.
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_corefoundation.CFURLCreateFromFileSystemRepresentation.restype = \
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ctypes.c_void_p
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_corefoundation.CFURLCreateFromFileSystemRepresentation.argtypes = \
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[ctypes.c_int, ctypes.c_char_p, ctypes.c_int, ctypes.c_bool]
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# Get a string representation of a URL.
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_corefoundation.CFURLGetString.restype = ctypes.c_void_p
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_corefoundation.CFURLGetString.argtypes = [ctypes.c_void_p]
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# Open an audio file for reading.
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_coreaudio.ExtAudioFileOpenURL.restype = ctypes.c_int
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_coreaudio.ExtAudioFileOpenURL.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
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# Set audio file property.
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_coreaudio.ExtAudioFileSetProperty.restype = ctypes.c_int
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_coreaudio.ExtAudioFileSetProperty.argtypes = \
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[ctypes.c_void_p, ctypes.c_uint, ctypes.c_uint, ctypes.c_void_p]
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# Get audio file property.
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_coreaudio.ExtAudioFileGetProperty.restype = ctypes.c_int
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_coreaudio.ExtAudioFileGetProperty.argtypes = \
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[ctypes.c_void_p, ctypes.c_uint, ctypes.c_void_p, ctypes.c_void_p]
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# Read from an audio file.
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_coreaudio.ExtAudioFileRead.restype = ctypes.c_int
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_coreaudio.ExtAudioFileRead.argtypes = \
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[ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]
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# Close/free an audio file.
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_coreaudio.ExtAudioFileDispose.restype = ctypes.c_int
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_coreaudio.ExtAudioFileDispose.argtypes = [ctypes.c_void_p]
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# Constants used in CoreAudio.
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def multi_char_literal(chars):
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"""Emulates character integer literals in C. Given a string "abc",
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returns the value of the C single-quoted literal 'abc'.
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"""
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num = 0
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for index, char in enumerate(chars):
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shift = (len(chars) - index - 1) * 8
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num |= ord(char) << shift
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return num
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PROP_FILE_DATA_FORMAT = multi_char_literal('ffmt')
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PROP_CLIENT_DATA_FORMAT = multi_char_literal('cfmt')
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PROP_LENGTH = multi_char_literal('#frm')
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AUDIO_ID_PCM = multi_char_literal('lpcm')
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PCM_IS_FLOAT = 1 << 0
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PCM_IS_BIG_ENDIAN = 1 << 1
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PCM_IS_SIGNED_INT = 1 << 2
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PCM_IS_PACKED = 1 << 3
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ERROR_TYPE = multi_char_literal('typ?')
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ERROR_FORMAT = multi_char_literal('fmt?')
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ERROR_NOT_FOUND = -43
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# Check for errors in functions that return error codes.
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class MacError(DecodeError):
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def __init__(self, code):
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if code == ERROR_TYPE:
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msg = 'unsupported audio type'
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elif code == ERROR_FORMAT:
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msg = 'unsupported format'
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else:
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msg = 'error %i' % code
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super().__init__(msg)
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def check(err):
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"""If err is nonzero, raise a MacError exception."""
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if err == ERROR_NOT_FOUND:
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raise OSError('file not found')
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elif err != 0:
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raise MacError(err)
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# CoreFoundation objects.
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class CFObject:
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def __init__(self, obj):
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if obj == 0:
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raise ValueError('object is zero')
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self._obj = obj
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def __del__(self):
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if _corefoundation:
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_corefoundation.CFRelease(self._obj)
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class CFURL(CFObject):
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def __init__(self, filename):
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if not isinstance(filename, bytes):
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filename = filename.encode(sys.getfilesystemencoding())
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filename = os.path.abspath(os.path.expanduser(filename))
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url = _corefoundation.CFURLCreateFromFileSystemRepresentation(
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0, filename, len(filename), False
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)
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super().__init__(url)
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def __str__(self):
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cfstr = _corefoundation.CFURLGetString(self._obj)
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out = _corefoundation.CFStringGetCStringPtr(cfstr, 0)
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# Resulting CFString does not need to be released according to docs.
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return out
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# Structs used in CoreAudio.
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class AudioStreamBasicDescription(ctypes.Structure):
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_fields_ = [
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("mSampleRate", ctypes.c_double),
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("mFormatID", ctypes.c_uint),
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("mFormatFlags", ctypes.c_uint),
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("mBytesPerPacket", ctypes.c_uint),
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("mFramesPerPacket", ctypes.c_uint),
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("mBytesPerFrame", ctypes.c_uint),
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("mChannelsPerFrame", ctypes.c_uint),
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("mBitsPerChannel", ctypes.c_uint),
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("mReserved", ctypes.c_uint),
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]
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class AudioBuffer(ctypes.Structure):
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_fields_ = [
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("mNumberChannels", ctypes.c_uint),
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("mDataByteSize", ctypes.c_uint),
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("mData", ctypes.c_void_p),
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]
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class AudioBufferList(ctypes.Structure):
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_fields_ = [
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("mNumberBuffers", ctypes.c_uint),
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("mBuffers", AudioBuffer * 1),
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]
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# Main functionality.
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class ExtAudioFile(AudioFile):
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"""A CoreAudio "extended audio file". Reads information and raw PCM
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audio data from any file that CoreAudio knows how to decode.
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>>> with ExtAudioFile('something.m4a') as f:
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>>> print f.samplerate
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>>> print f.channels
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>>> print f.duration
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>>> for block in f:
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>>> do_something(block)
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"""
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def __init__(self, filename):
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url = CFURL(filename)
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try:
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self._obj = self._open_url(url)
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except:
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self.closed = True
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raise
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del url
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self.closed = False
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self._file_fmt = None
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self._client_fmt = None
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self.setup()
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@classmethod
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def _open_url(cls, url):
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"""Given a CFURL Python object, return an opened ExtAudioFileRef.
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"""
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file_obj = ctypes.c_void_p()
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check(_coreaudio.ExtAudioFileOpenURL(
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url._obj, ctypes.byref(file_obj)
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))
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return file_obj
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def set_client_format(self, desc):
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"""Get the client format description. This describes the
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encoding of the data that the program will read from this
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object.
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"""
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assert desc.mFormatID == AUDIO_ID_PCM
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check(_coreaudio.ExtAudioFileSetProperty(
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self._obj, PROP_CLIENT_DATA_FORMAT, ctypes.sizeof(desc),
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ctypes.byref(desc)
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))
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self._client_fmt = desc
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def get_file_format(self):
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"""Get the file format description. This describes the type of
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data stored on disk.
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"""
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# Have cached file format?
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if self._file_fmt is not None:
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return self._file_fmt
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# Make the call to retrieve it.
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desc = AudioStreamBasicDescription()
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size = ctypes.c_int(ctypes.sizeof(desc))
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check(_coreaudio.ExtAudioFileGetProperty(
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self._obj, PROP_FILE_DATA_FORMAT, ctypes.byref(size),
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ctypes.byref(desc)
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))
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# Cache result.
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self._file_fmt = desc
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return desc
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@property
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def channels(self):
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"""The number of channels in the audio source."""
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return int(self.get_file_format().mChannelsPerFrame)
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@property
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def samplerate(self):
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"""Gets the sample rate of the audio."""
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return int(self.get_file_format().mSampleRate)
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@property
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def duration(self):
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"""Gets the length of the file in seconds (a float)."""
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return float(self.nframes) / self.samplerate
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@property
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def nframes(self):
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"""Gets the number of frames in the source file."""
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length = ctypes.c_long()
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size = ctypes.c_int(ctypes.sizeof(length))
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check(_coreaudio.ExtAudioFileGetProperty(
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self._obj, PROP_LENGTH, ctypes.byref(size), ctypes.byref(length)
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))
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return length.value
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def setup(self, bitdepth=16):
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"""Set the client format parameters, specifying the desired PCM
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audio data format to be read from the file. Must be called
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before reading from the file.
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"""
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fmt = self.get_file_format()
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newfmt = copy.copy(fmt)
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newfmt.mFormatID = AUDIO_ID_PCM
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newfmt.mFormatFlags = \
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PCM_IS_SIGNED_INT | PCM_IS_PACKED
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newfmt.mBitsPerChannel = bitdepth
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newfmt.mBytesPerPacket = \
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(fmt.mChannelsPerFrame * newfmt.mBitsPerChannel // 8)
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newfmt.mFramesPerPacket = 1
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newfmt.mBytesPerFrame = newfmt.mBytesPerPacket
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self.set_client_format(newfmt)
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def read_data(self, blocksize=4096):
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"""Generates byte strings reflecting the audio data in the file.
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"""
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frames = ctypes.c_uint(blocksize // self._client_fmt.mBytesPerFrame)
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buf = ctypes.create_string_buffer(blocksize)
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buflist = AudioBufferList()
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buflist.mNumberBuffers = 1
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buflist.mBuffers[0].mNumberChannels = \
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self._client_fmt.mChannelsPerFrame
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buflist.mBuffers[0].mDataByteSize = blocksize
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buflist.mBuffers[0].mData = ctypes.cast(buf, ctypes.c_void_p)
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while True:
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check(_coreaudio.ExtAudioFileRead(
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self._obj, ctypes.byref(frames), ctypes.byref(buflist)
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))
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assert buflist.mNumberBuffers == 1
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size = buflist.mBuffers[0].mDataByteSize
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if not size:
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break
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data = ctypes.cast(buflist.mBuffers[0].mData,
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ctypes.POINTER(ctypes.c_char))
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blob = data[:size]
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yield blob
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def close(self):
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"""Close the audio file and free associated memory."""
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if not self.closed:
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check(_coreaudio.ExtAudioFileDispose(self._obj))
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self.closed = True
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def __del__(self):
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if _coreaudio:
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self.close()
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# Context manager methods.
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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self.close()
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return False
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# Iteration.
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def __iter__(self):
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return self.read_data()
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