150 lines
4.2 KiB
Python
150 lines
4.2 KiB
Python
# 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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"""Uses standard-library modules to read AIFF, AIFF-C, and WAV files."""
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import aifc
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import audioop
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import struct
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import sunau
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import wave
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from .exceptions import DecodeError
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from .base import AudioFile
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# Produce two-byte (16-bit) output samples.
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TARGET_WIDTH = 2
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# Python 3.4 added support for 24-bit (3-byte) samples.
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SUPPORTED_WIDTHS = (1, 2, 3, 4)
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class UnsupportedError(DecodeError):
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"""File is not an AIFF, WAV, or Au file."""
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class BitWidthError(DecodeError):
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"""The file uses an unsupported bit width."""
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def byteswap(s):
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"""Swaps the endianness of the bytestring s, which must be an array
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of shorts (16-bit signed integers). This is probably less efficient
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than it should be.
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"""
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assert len(s) % 2 == 0
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parts = []
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for i in range(0, len(s), 2):
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chunk = s[i:i + 2]
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newchunk = struct.pack('<h', *struct.unpack('>h', chunk))
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parts.append(newchunk)
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return b''.join(parts)
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class RawAudioFile(AudioFile):
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"""An AIFF, WAV, or Au file that can be read by the Python standard
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library modules ``wave``, ``aifc``, and ``sunau``.
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"""
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def __init__(self, filename):
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self._fh = open(filename, 'rb')
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try:
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self._file = aifc.open(self._fh)
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except aifc.Error:
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# Return to the beginning of the file to try the next reader.
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self._fh.seek(0)
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else:
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self._needs_byteswap = True
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self._check()
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return
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try:
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self._file = wave.open(self._fh)
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except wave.Error:
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self._fh.seek(0)
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pass
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else:
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self._needs_byteswap = False
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self._check()
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return
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try:
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self._file = sunau.open(self._fh)
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except sunau.Error:
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self._fh.seek(0)
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pass
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else:
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self._needs_byteswap = True
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self._check()
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return
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# None of the three libraries could open the file.
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self._fh.close()
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raise UnsupportedError()
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def _check(self):
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"""Check that the files' parameters allow us to decode it and
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raise an error otherwise.
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"""
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if self._file.getsampwidth() not in SUPPORTED_WIDTHS:
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self.close()
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raise BitWidthError()
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def close(self):
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"""Close the underlying file."""
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self._file.close()
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self._fh.close()
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@property
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def channels(self):
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"""Number of audio channels."""
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return self._file.getnchannels()
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@property
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def samplerate(self):
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"""Sample rate in Hz."""
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return self._file.getframerate()
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@property
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def duration(self):
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"""Length of the audio in seconds (a float)."""
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return float(self._file.getnframes()) / self.samplerate
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def read_data(self, block_samples=1024):
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"""Generates blocks of PCM data found in the file."""
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old_width = self._file.getsampwidth()
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while True:
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data = self._file.readframes(block_samples)
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if not data:
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break
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# Make sure we have the desired bitdepth and endianness.
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data = audioop.lin2lin(data, old_width, TARGET_WIDTH)
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if self._needs_byteswap and self._file.getcomptype() != 'sowt':
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# Big-endian data. Swap endianness.
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data = byteswap(data)
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yield data
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# Context manager.
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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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