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406 lines
12 KiB
Python
406 lines
12 KiB
Python
"""
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Module to read / write wav files using numpy arrays
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Functions
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---------
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`read`: Return the sample rate (in samples/sec) and data from a WAV file.
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`write`: Write a numpy array as a WAV file.
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"""
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from __future__ import division, print_function, absolute_import
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import sys
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import numpy
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import struct
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import warnings
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__all__ = [
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'WavFileWarning',
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'read',
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'write'
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]
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class WavFileWarning(UserWarning):
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pass
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WAVE_FORMAT_PCM = 0x0001
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WAVE_FORMAT_IEEE_FLOAT = 0x0003
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WAVE_FORMAT_EXTENSIBLE = 0xfffe
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KNOWN_WAVE_FORMATS = (WAVE_FORMAT_PCM, WAVE_FORMAT_IEEE_FLOAT)
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# assumes file pointer is immediately
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# after the 'fmt ' id
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def _read_fmt_chunk(fid, is_big_endian):
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"""
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Returns
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-------
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size : int
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size of format subchunk in bytes (minus 8 for "fmt " and itself)
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format_tag : int
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PCM, float, or compressed format
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channels : int
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number of channels
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fs : int
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sampling frequency in samples per second
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bytes_per_second : int
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overall byte rate for the file
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block_align : int
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bytes per sample, including all channels
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bit_depth : int
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bits per sample
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"""
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if is_big_endian:
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fmt = '>'
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else:
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fmt = '<'
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size = res = struct.unpack(fmt+'I', fid.read(4))[0]
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bytes_read = 0
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if size < 16:
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raise ValueError("Binary structure of wave file is not compliant")
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res = struct.unpack(fmt+'HHIIHH', fid.read(16))
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bytes_read += 16
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format_tag, channels, fs, bytes_per_second, block_align, bit_depth = res
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if format_tag == WAVE_FORMAT_EXTENSIBLE and size >= (16+2):
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ext_chunk_size = struct.unpack(fmt+'H', fid.read(2))[0]
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bytes_read += 2
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if ext_chunk_size >= 22:
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extensible_chunk_data = fid.read(22)
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bytes_read += 22
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raw_guid = extensible_chunk_data[2+4:2+4+16]
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# GUID template {XXXXXXXX-0000-0010-8000-00AA00389B71} (RFC-2361)
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# MS GUID byte order: first three groups are native byte order,
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# rest is Big Endian
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if is_big_endian:
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tail = b'\x00\x00\x00\x10\x80\x00\x00\xAA\x00\x38\x9B\x71'
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else:
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tail = b'\x00\x00\x10\x00\x80\x00\x00\xAA\x00\x38\x9B\x71'
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if raw_guid.endswith(tail):
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format_tag = struct.unpack(fmt+'I', raw_guid[:4])[0]
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else:
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raise ValueError("Binary structure of wave file is not compliant")
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if format_tag not in KNOWN_WAVE_FORMATS:
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raise ValueError("Unknown wave file format")
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# move file pointer to next chunk
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if size > (bytes_read):
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fid.read(size - bytes_read)
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return (size, format_tag, channels, fs, bytes_per_second, block_align,
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bit_depth)
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# assumes file pointer is immediately after the 'data' id
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def _read_data_chunk(fid, format_tag, channels, bit_depth, is_big_endian,
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mmap=False):
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if is_big_endian:
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fmt = '>I'
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else:
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fmt = '<I'
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# Size of the data subchunk in bytes
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size = struct.unpack(fmt, fid.read(4))[0]
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# Number of bytes per sample
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bytes_per_sample = bit_depth//8
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if bit_depth == 8:
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dtype = 'u1'
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else:
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if is_big_endian:
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dtype = '>'
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else:
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dtype = '<'
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if format_tag == WAVE_FORMAT_PCM:
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dtype += 'i%d' % bytes_per_sample
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else:
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dtype += 'f%d' % bytes_per_sample
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if not mmap:
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data = numpy.frombuffer(fid.read(size), dtype=dtype)
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else:
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start = fid.tell()
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data = numpy.memmap(fid, dtype=dtype, mode='c', offset=start,
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shape=(size//bytes_per_sample,))
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fid.seek(start + size)
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if channels > 1:
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data = data.reshape(-1, channels)
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return data
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def _skip_unknown_chunk(fid, is_big_endian):
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if is_big_endian:
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fmt = '>I'
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else:
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fmt = '<I'
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data = fid.read(4)
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# call unpack() and seek() only if we have really read data from file
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# otherwise empty read at the end of the file would trigger
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# unnecessary exception at unpack() call
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# in case data equals somehow to 0, there is no need for seek() anyway
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if data:
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size = struct.unpack(fmt, data)[0]
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fid.seek(size, 1)
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def _read_riff_chunk(fid):
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str1 = fid.read(4) # File signature
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if str1 == b'RIFF':
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is_big_endian = False
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fmt = '<I'
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elif str1 == b'RIFX':
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is_big_endian = True
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fmt = '>I'
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else:
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# There are also .wav files with "FFIR" or "XFIR" signatures?
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raise ValueError("File format {}... not "
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"understood.".format(repr(str1)))
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# Size of entire file
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file_size = struct.unpack(fmt, fid.read(4))[0] + 8
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str2 = fid.read(4)
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if str2 != b'WAVE':
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raise ValueError("Not a WAV file.")
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return file_size, is_big_endian
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def read(filename, mmap=False):
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"""
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Open a WAV file
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Return the sample rate (in samples/sec) and data from a WAV file.
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Parameters
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----------
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filename : string or open file handle
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Input wav file.
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mmap : bool, optional
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Whether to read data as memory-mapped.
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Only to be used on real files (Default: False).
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.. versionadded:: 0.12.0
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Returns
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-------
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rate : int
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Sample rate of wav file.
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data : numpy array
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Data read from wav file. Data-type is determined from the file;
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see Notes.
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Notes
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-----
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This function cannot read wav files with 24-bit data.
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Common data types: [1]_
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===================== =========== =========== =============
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WAV format Min Max NumPy dtype
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===================== =========== =========== =============
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32-bit floating-point -1.0 +1.0 float32
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32-bit PCM -2147483648 +2147483647 int32
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16-bit PCM -32768 +32767 int16
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8-bit PCM 0 255 uint8
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===================== =========== =========== =============
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Note that 8-bit PCM is unsigned.
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References
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----------
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.. [1] IBM Corporation and Microsoft Corporation, "Multimedia Programming
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Interface and Data Specifications 1.0", section "Data Format of the
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Samples", August 1991
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http://www.tactilemedia.com/info/MCI_Control_Info.html
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"""
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if hasattr(filename, 'read'):
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fid = filename
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mmap = False
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else:
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fid = open(filename, 'rb')
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try:
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file_size, is_big_endian = _read_riff_chunk(fid)
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fmt_chunk_received = False
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channels = 1
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bit_depth = 8
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format_tag = WAVE_FORMAT_PCM
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while fid.tell() < file_size:
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# read the next chunk
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chunk_id = fid.read(4)
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if not chunk_id:
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raise ValueError("Unexpected end of file.")
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elif len(chunk_id) < 4:
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raise ValueError("Incomplete wav chunk.")
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if chunk_id == b'fmt ':
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fmt_chunk_received = True
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fmt_chunk = _read_fmt_chunk(fid, is_big_endian)
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format_tag, channels, fs = fmt_chunk[1:4]
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bit_depth = fmt_chunk[6]
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if bit_depth not in (8, 16, 32, 64, 96, 128):
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raise ValueError("Unsupported bit depth: the wav file "
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"has {}-bit data.".format(bit_depth))
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elif chunk_id == b'fact':
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_skip_unknown_chunk(fid, is_big_endian)
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elif chunk_id == b'data':
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if not fmt_chunk_received:
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raise ValueError("No fmt chunk before data")
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data = _read_data_chunk(fid, format_tag, channels, bit_depth,
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is_big_endian, mmap)
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elif chunk_id == b'LIST':
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# Someday this could be handled properly but for now skip it
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_skip_unknown_chunk(fid, is_big_endian)
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elif chunk_id in (b'JUNK', b'Fake'):
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# Skip alignment chunks without warning
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_skip_unknown_chunk(fid, is_big_endian)
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else:
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warnings.warn("Chunk (non-data) not understood, skipping it.",
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WavFileWarning)
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_skip_unknown_chunk(fid, is_big_endian)
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finally:
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if not hasattr(filename, 'read'):
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fid.close()
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else:
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fid.seek(0)
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return fs, data
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def write(filename, rate, data):
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"""
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Write a numpy array as a WAV file.
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Parameters
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----------
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filename : string or open file handle
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Output wav file.
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rate : int
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The sample rate (in samples/sec).
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data : ndarray
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A 1-D or 2-D numpy array of either integer or float data-type.
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Notes
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-----
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* Writes a simple uncompressed WAV file.
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* To write multiple-channels, use a 2-D array of shape
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(Nsamples, Nchannels).
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* The bits-per-sample and PCM/float will be determined by the data-type.
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Common data types: [1]_
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===================== =========== =========== =============
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WAV format Min Max NumPy dtype
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===================== =========== =========== =============
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32-bit floating-point -1.0 +1.0 float32
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32-bit PCM -2147483648 +2147483647 int32
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16-bit PCM -32768 +32767 int16
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8-bit PCM 0 255 uint8
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===================== =========== =========== =============
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Note that 8-bit PCM is unsigned.
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References
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----------
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.. [1] IBM Corporation and Microsoft Corporation, "Multimedia Programming
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Interface and Data Specifications 1.0", section "Data Format of the
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Samples", August 1991
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http://www.tactilemedia.com/info/MCI_Control_Info.html
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"""
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if hasattr(filename, 'write'):
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fid = filename
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else:
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fid = open(filename, 'wb')
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fs = rate
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try:
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dkind = data.dtype.kind
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if not (dkind == 'i' or dkind == 'f' or (dkind == 'u' and
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data.dtype.itemsize == 1)):
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raise ValueError("Unsupported data type '%s'" % data.dtype)
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header_data = b''
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header_data += b'RIFF'
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header_data += b'\x00\x00\x00\x00'
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header_data += b'WAVE'
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# fmt chunk
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header_data += b'fmt '
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if dkind == 'f':
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format_tag = WAVE_FORMAT_IEEE_FLOAT
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else:
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format_tag = WAVE_FORMAT_PCM
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if data.ndim == 1:
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channels = 1
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else:
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channels = data.shape[1]
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bit_depth = data.dtype.itemsize * 8
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bytes_per_second = fs*(bit_depth // 8)*channels
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block_align = channels * (bit_depth // 8)
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fmt_chunk_data = struct.pack('<HHIIHH', format_tag, channels, fs,
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bytes_per_second, block_align, bit_depth)
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if not (dkind == 'i' or dkind == 'u'):
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# add cbSize field for non-PCM files
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fmt_chunk_data += b'\x00\x00'
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header_data += struct.pack('<I', len(fmt_chunk_data))
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header_data += fmt_chunk_data
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# fact chunk (non-PCM files)
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if not (dkind == 'i' or dkind == 'u'):
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header_data += b'fact'
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header_data += struct.pack('<II', 4, data.shape[0])
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# check data size (needs to be immediately before the data chunk)
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if ((len(header_data)-4-4) + (4+4+data.nbytes)) > 0xFFFFFFFF:
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raise ValueError("Data exceeds wave file size limit")
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fid.write(header_data)
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# data chunk
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fid.write(b'data')
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fid.write(struct.pack('<I', data.nbytes))
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if data.dtype.byteorder == '>' or (data.dtype.byteorder == '=' and
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sys.byteorder == 'big'):
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data = data.byteswap()
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_array_tofile(fid, data)
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# Determine file size and place it in correct
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# position at start of the file.
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size = fid.tell()
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fid.seek(4)
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fid.write(struct.pack('<I', size-8))
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finally:
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if not hasattr(filename, 'write'):
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fid.close()
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else:
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fid.seek(0)
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if sys.version_info[0] >= 3:
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def _array_tofile(fid, data):
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# ravel gives a c-contiguous buffer
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fid.write(data.ravel().view('b').data)
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else:
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def _array_tofile(fid, data):
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fid.write(data.tostring())
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