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"""
Module to read / write wav files using numpy arrays
Functions
---------
`read`: Return the sample rate (in samples/sec) and data from a WAV file.
`write`: Write a numpy array as a WAV file.
"""
import numpy
from numpy.compat import asbytes
import struct
import warnings
class WavFileWarning(UserWarning):
pass
_big_endian = False
# assumes file pointer is immediately
# after the 'fmt ' id
def _read_fmt_chunk(fid):
if _big_endian:
fmt = '>'
else:
fmt = '<'
res = struct.unpack(fmt+'ihHIIHH',fid.read(20))
size, comp, noc, rate, sbytes, ba, bits = res
if (comp != 1 or size > 16):
warnings.warn("Unfamiliar format bytes", WavFileWarning)
if (size>16):
fid.read(size-16)
return size, comp, noc, rate, sbytes, ba, bits
# assumes file pointer is immediately
# after the 'data' id
def _read_data_chunk(fid, noc, bits):
if _big_endian:
fmt = '>i'
else:
fmt = '<i'
size = struct.unpack(fmt,fid.read(4))[0]
if bits == 8:
data = numpy.fromfile(fid, dtype=numpy.ubyte, count=size)
if noc > 1:
data = data.reshape(-1,noc)
else:
bytes = bits//8
if _big_endian:
dtype = '>i%d' % bytes
else:
dtype = '<i%d' % bytes
data = numpy.fromfile(fid, dtype=dtype, count=size//bytes)
if noc > 1:
data = data.reshape(-1,noc)
return data
def _read_riff_chunk(fid):
global _big_endian
str1 = fid.read(4)
if str1 == asbytes('RIFX'):
_big_endian = True
elif str1 != asbytes('RIFF'):
raise ValueError("Not a WAV file.")
if _big_endian:
fmt = '>I'
else:
fmt = '<I'
fsize = struct.unpack(fmt, fid.read(4))[0] + 8
str2 = fid.read(4)
if (str2 != asbytes('WAVE')):
raise ValueError("Not a WAV file.")
if str1 == asbytes('RIFX'):
_big_endian = True
return fsize
# open a wave-file
def read(file):
"""
Return the sample rate (in samples/sec) and data from a WAV file
Parameters
----------
file : file
Input wav file.
Returns
-------
rate : int
Sample rate of wav file
data : numpy array
Data read from wav file
Notes
-----
* The file can be an open file or a filename.
* The returned sample rate is a Python integer
* The data is returned as a numpy array with a
data-type determined from the file.
"""
if hasattr(file,'read'):
fid = file
else:
fid = open(file, 'rb')
fsize = _read_riff_chunk(fid)
noc = 1
bits = 8
while (fid.tell() < fsize):
# read the next chunk
chunk_id = fid.read(4)
if chunk_id == asbytes('fmt '):
size, comp, noc, rate, sbytes, ba, bits = _read_fmt_chunk(fid)
elif chunk_id == asbytes('data'):
data = _read_data_chunk(fid, noc, bits)
else:
warnings.warn("chunk not understood", WavFileWarning)
data = fid.read(4)
if _big_endian:
fmt = '>i'
else:
fmt = '<i'
size = struct.unpack(fmt, data)[0]
fid.seek(size, 1)
fid.close()
return rate, data
# Write a wave-file
# sample rate, data
def write(filename, rate, data):
"""
Write a numpy array as a WAV file
Parameters
----------
filename : file
The name of the file to write (will be over-written).
rate : int
The sample rate (in samples/sec).
data : ndarray
A 1-D or 2-D numpy array of integer data-type.
Notes
-----
* Writes a simple uncompressed WAV file.
* The bits-per-sample will be determined by the data-type.
* To write multiple-channels, use a 2-D array of shape
(Nsamples, Nchannels).
"""
fid = open(filename, 'wb')
fid.write(asbytes('RIFF'))
fid.write(asbytes('\x00\x00\x00\x00'))
fid.write(asbytes('WAVE'))
# fmt chunk
fid.write(asbytes('fmt '))
if data.ndim == 1:
noc = 1
else:
noc = data.shape[1]
bits = data.dtype.itemsize * 8
sbytes = rate*(bits // 8)*noc
ba = noc * (bits // 8)
fid.write(struct.pack('<ihHIIHH', 16, 1, noc, rate, sbytes, ba, bits))
# data chunk
fid.write(asbytes('data'))
fid.write(struct.pack('<i', data.nbytes))
import sys
if data.dtype.byteorder == '>' or (data.dtype.byteorder == '=' and sys.byteorder == 'big'):
data = data.byteswap()
data.tofile(fid)
# Determine file size and place it in correct
# position at start of the file.
size = fid.tell()
fid.seek(4)
fid.write(struct.pack('<i', size-8))
fid.close()
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