400 lines (327 sloc) 12.1 KB
"""
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.
"""
from __future__ import division, print_function, absolute_import
import sys
import numpy
import struct
import warnings
__all__ = [
'WavFileWarning',
'read',
'write'
]
class WavFileWarning(UserWarning):
pass
WAVE_FORMAT_PCM = 0x0001
WAVE_FORMAT_IEEE_FLOAT = 0x0003
WAVE_FORMAT_EXTENSIBLE = 0xfffe
KNOWN_WAVE_FORMATS = (WAVE_FORMAT_PCM, WAVE_FORMAT_IEEE_FLOAT)
# assumes file pointer is immediately
# after the 'fmt ' id
def _read_fmt_chunk(fid, is_big_endian):
"""
Returns
-------
size : int
size of format subchunk in bytes (minus 8 for "fmt " and itself)
format_tag : int
PCM, float, or compressed format
channels : int
number of channels
fs : int
sampling frequency in samples per second
bytes_per_second : int
overall byte rate for the file
block_align : int
bytes per sample, including all channels
bit_depth : int
bits per sample
"""
if is_big_endian:
fmt = '>'
else:
fmt = '<'
size = res = struct.unpack(fmt+'I', fid.read(4))[0]
bytes_read = 0
if size < 16:
raise ValueError("Binary structure of wave file is not compliant")
res = struct.unpack(fmt+'HHIIHH', fid.read(16))
bytes_read += 16
format_tag, channels, fs, bytes_per_second, block_align, bit_depth = res
if format_tag == WAVE_FORMAT_EXTENSIBLE and size >= (16+2):
ext_chunk_size = struct.unpack(fmt+'H', fid.read(2))[0]
bytes_read += 2
if ext_chunk_size >= 22:
extensible_chunk_data = fid.read(22)
bytes_read += 22
raw_guid = extensible_chunk_data[2+4:2+4+16]
# GUID template {XXXXXXXX-0000-0010-8000-00AA00389B71} (RFC-2361)
# MS GUID byte order: first three groups are native byte order,
# rest is Big Endian
if is_big_endian:
tail = b'\x00\x00\x00\x10\x80\x00\x00\xAA\x00\x38\x9B\x71'
else:
tail = b'\x00\x00\x10\x00\x80\x00\x00\xAA\x00\x38\x9B\x71'
if raw_guid.endswith(tail):
format_tag = struct.unpack(fmt+'I', raw_guid[:4])[0]
else:
raise ValueError("Binary structure of wave file is not compliant")
if format_tag not in KNOWN_WAVE_FORMATS:
raise ValueError("Unknown wave file format")
# move file pointer to next chunk
if size > (bytes_read):
fid.read(size - bytes_read)
return (size, format_tag, channels, fs, bytes_per_second, block_align,
bit_depth)
# assumes file pointer is immediately after the 'data' id
def _read_data_chunk(fid, format_tag, channels, bit_depth, is_big_endian,
mmap=False):
if is_big_endian:
fmt = '>I'
else:
fmt = '<I'
# Size of the data subchunk in bytes
size = struct.unpack(fmt, fid.read(4))[0]
# Number of bytes per sample
bytes_per_sample = bit_depth//8
if bit_depth == 8:
dtype = 'u1'
else:
if is_big_endian:
dtype = '>'
else:
dtype = '<'
if format_tag == WAVE_FORMAT_PCM:
dtype += 'i%d' % bytes_per_sample
else:
dtype += 'f%d' % bytes_per_sample
if not mmap:
data = numpy.fromstring(fid.read(size), dtype=dtype)
else:
start = fid.tell()
data = numpy.memmap(fid, dtype=dtype, mode='c', offset=start,
shape=(size//bytes_per_sample,))
fid.seek(start + size)
if channels > 1:
data = data.reshape(-1, channels)
return data
def _skip_unknown_chunk(fid, is_big_endian):
if is_big_endian:
fmt = '>I'
else:
fmt = '<I'
data = fid.read(4)
# call unpack() and seek() only if we have really read data from file
# otherwise empty read at the end of the file would trigger
# unnecessary exception at unpack() call
# in case data equals somehow to 0, there is no need for seek() anyway
if data:
size = struct.unpack(fmt, data)[0]
fid.seek(size, 1)
def _read_riff_chunk(fid):
str1 = fid.read(4) # File signature
if str1 == b'RIFF':
is_big_endian = False
fmt = '<I'
elif str1 == b'RIFX':
is_big_endian = True
fmt = '>I'
else:
# There are also .wav files with "FFIR" or "XFIR" signatures?
raise ValueError("File format {}... not "
"understood.".format(repr(str1)))
# Size of entire file
file_size = struct.unpack(fmt, fid.read(4))[0] + 8
str2 = fid.read(4)
if str2 != b'WAVE':
raise ValueError("Not a WAV file.")
return file_size, is_big_endian
def read(filename, mmap=False):
"""
Open a WAV file
Return the sample rate (in samples/sec) and data from a WAV file.
Parameters
----------
filename : string or open file handle
Input wav file.
mmap : bool, optional
Whether to read data as memory-mapped.
Only to be used on real files (Default: False).
.. versionadded:: 0.12.0
Returns
-------
rate : int
Sample rate of wav file.
data : numpy array
Data read from wav file. Data-type is determined from the file;
see Notes.
Notes
-----
This function cannot read wav files with 24-bit data.
Common data types: [1]_
===================== =========== =========== =============
WAV format Min Max NumPy dtype
===================== =========== =========== =============
32-bit floating-point -1.0 +1.0 float32
32-bit PCM -2147483648 +2147483647 int32
16-bit PCM -32768 +32767 int16
8-bit PCM 0 255 uint8
===================== =========== =========== =============
Note that 8-bit PCM is unsigned.
References
----------
.. [1] IBM Corporation and Microsoft Corporation, "Multimedia Programming
Interface and Data Specifications 1.0", section "Data Format of the
Samples", August 1991
http://www-mmsp.ece.mcgill.ca/documents/audioformats/wave/Docs/riffmci.pdf
"""
if hasattr(filename, 'read'):
fid = filename
mmap = False
else:
fid = open(filename, 'rb')
try:
file_size, is_big_endian = _read_riff_chunk(fid)
fmt_chunk_received = False
channels = 1
bit_depth = 8
format_tag = WAVE_FORMAT_PCM
while fid.tell() < file_size:
# read the next chunk
chunk_id = fid.read(4)
if chunk_id == b'fmt ':
fmt_chunk_received = True
fmt_chunk = _read_fmt_chunk(fid, is_big_endian)
format_tag, channels, fs = fmt_chunk[1:4]
bit_depth = fmt_chunk[6]
if bit_depth not in (8, 16, 32, 64, 96, 128):
raise ValueError("Unsupported bit depth: the wav file "
"has {}-bit data.".format(bit_depth))
elif chunk_id == b'fact':
_skip_unknown_chunk(fid, is_big_endian)
elif chunk_id == b'data':
if not fmt_chunk_received:
raise ValueError("No fmt chunk before data")
data = _read_data_chunk(fid, format_tag, channels, bit_depth,
is_big_endian, mmap)
elif chunk_id == b'LIST':
# Someday this could be handled properly but for now skip it
_skip_unknown_chunk(fid, is_big_endian)
elif chunk_id in (b'JUNK', b'Fake'):
# Skip alignment chunks without warning
_skip_unknown_chunk(fid, is_big_endian)
else:
warnings.warn("Chunk (non-data) not understood, skipping it.",
WavFileWarning)
_skip_unknown_chunk(fid, is_big_endian)
finally:
if not hasattr(filename, 'read'):
fid.close()
else:
fid.seek(0)
return fs, data
def write(filename, rate, data):
"""
Write a numpy array as a WAV file.
Parameters
----------
filename : string or open file handle
Output wav file.
rate : int
The sample rate (in samples/sec).
data : ndarray
A 1-D or 2-D numpy array of either integer or float data-type.
Notes
-----
* Writes a simple uncompressed WAV file.
* To write multiple-channels, use a 2-D array of shape
(Nsamples, Nchannels).
* The bits-per-sample and PCM/float will be determined by the data-type.
Common data types: [1]_
===================== =========== =========== =============
WAV format Min Max NumPy dtype
===================== =========== =========== =============
32-bit floating-point -1.0 +1.0 float32
32-bit PCM -2147483648 +2147483647 int32
16-bit PCM -32768 +32767 int16
8-bit PCM 0 255 uint8
===================== =========== =========== =============
Note that 8-bit PCM is unsigned.
References
----------
.. [1] IBM Corporation and Microsoft Corporation, "Multimedia Programming
Interface and Data Specifications 1.0", section "Data Format of the
Samples", August 1991
http://www-mmsp.ece.mcgill.ca/documents/audioformats/wave/Docs/riffmci.pdf
"""
if hasattr(filename, 'write'):
fid = filename
else:
fid = open(filename, 'wb')
fs = rate
try:
dkind = data.dtype.kind
if not (dkind == 'i' or dkind == 'f' or (dkind == 'u' and
data.dtype.itemsize == 1)):
raise ValueError("Unsupported data type '%s'" % data.dtype)
header_data = b''
header_data += b'RIFF'
header_data += b'\x00\x00\x00\x00'
header_data += b'WAVE'
# fmt chunk
header_data += b'fmt '
if dkind == 'f':
format_tag = WAVE_FORMAT_IEEE_FLOAT
else:
format_tag = WAVE_FORMAT_PCM
if data.ndim == 1:
channels = 1
else:
channels = data.shape[1]
bit_depth = data.dtype.itemsize * 8
bytes_per_second = fs*(bit_depth // 8)*channels
block_align = channels * (bit_depth // 8)
fmt_chunk_data = struct.pack('<HHIIHH', format_tag, channels, fs,
bytes_per_second, block_align, bit_depth)
if not (dkind == 'i' or dkind == 'u'):
# add cbSize field for non-PCM files
fmt_chunk_data += b'\x00\x00'
header_data += struct.pack('<I', len(fmt_chunk_data))
header_data += fmt_chunk_data
# fact chunk (non-PCM files)
if not (dkind == 'i' or dkind == 'u'):
header_data += b'fact'
header_data += struct.pack('<II', 4, data.shape[0])
# check data size (needs to be immediately before the data chunk)
if ((len(header_data)-4-4) + (4+4+data.nbytes)) > 0xFFFFFFFF:
raise ValueError("Data exceeds wave file size limit")
fid.write(header_data)
# data chunk
fid.write(b'data')
fid.write(struct.pack('<I', data.nbytes))
if data.dtype.byteorder == '>' or (data.dtype.byteorder == '=' and
sys.byteorder == 'big'):
data = data.byteswap()
_array_tofile(fid, data)
# 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))
finally:
if not hasattr(filename, 'write'):
fid.close()
else:
fid.seek(0)
if sys.version_info[0] >= 3:
def _array_tofile(fid, data):
# ravel gives a c-contiguous buffer
fid.write(data.ravel().view('b').data)
else:
def _array_tofile(fid, data):
fid.write(data.tostring())