Python 音频处理：wave

1. 概述

wave 模块提供了一个处理 WAV 声音格式的便利接口。它不支持压缩/解压，但是支持单声道/立体声。

用法：wave.open(file, mode=None)，其中，mode为rb 和 wb：

• rb：生成 wav_read 对象
• wb：生成 wav_write 对象
  注意不支持同时读写。

注：关于 r、w、rb、wb
r和w是普通读和写文件（简单理解为人工编写的文件）；
rb和wb是读写二进制文件（简单理解为可以操作图片等非手工编写的文件）

1.1 Wave_read对象

import wave

# wave.read 对象方法

wr = wave.open('/Users/robin/Desktop/WavTest.wav', 'rb')

print(wr.getnchannels()) # 返回声道数量（1 为单声道，2 为立体声）
print(wr.getsampwidth()) # 返回采样字节长度
print(wr.getframerate()) # 返回采样频率
print(wr.getnframes()) # 返回音频总的帧数

print(wr.getparams()) # 返回一个 namedtuple() (nchannels, sampwidth, framerate, nframes, comptype, compname)，与 get*() 方法的输出相同。

print(wr.readframes(n))

1
2
16000
103765
_wave_params(nchannels=1, sampwidth=2, framerate=16000, nframes=103765, comptype='NONE', compname='not compressed')
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0
...

1.2 Wave_write 对象

# wave.write 对象方法
#（1）open 创建文件
ww = wave.open('/Users/robin/Desktop/WavTest.wav', 'wb')

#（2）set 设置参数
ww.setchannels(n) # 设置通道数
ww.setsampwidth(n) # 设置采样字节长度为 n
ww.setframerate(n) # 设置采样频率为 n

ww.setparams(n) # 设置所有形参，(nchannels, sampwidth, framerate, nframes, comptype, compname)，每项的值应可用于 set*() 方法。

# (3) writeframes 写入数据流
ww.writeframes(data) # 写入音频帧并确保 nframes 是正确的

# (4) close 关闭
ww.close()

2. 实际使用中的问题

2.1 音频保存

1、setsampwidth：采样字节长度 or 采样位数、量化位数

表示用多少bit表达一次采样所采集的数据，通常有8bit、16bit、24bit和32bit等几种，
需要注意的是，在设置setsampwidth时，采用的单位是bytes而不是bit。比如，16 bits per sample (= 2 bytes)，应该设置setsampwidth=2而不是setsampwidth=16，否则可能会报错：raise Error('sample width not specified')

代码示例：

channel = 1
bits = 2  # 16 bits = 2 bytes(wave模块中使用byte！！！注意除以8进行转换)
rates = 16000

# read（or resample） wav and save
def write_wav(file_name, input_data):
    wavfile = wave.open(file_name, 'wb')  # 创建（空）文件
    wavfile.setparams((channel, bits,  rates, 0, 'NONE', 'NONE'))
    print("wav文件信息：", wavfile.getparams()[:4])
    wavfile.writeframes(input_data)  # 写入数据
    wavfile.close()

3. 源代码：Lib/wave.py

"""Stuff to parse WAVE files.
Usage.
Reading WAVE files:
      f = wave.open(file, 'r')
where file is either the name of a file or an open file pointer.
The open file pointer must have methods read(), seek(), and close().
When the setpos() and rewind() methods are not used, the seek()
method is not  necessary.
This returns an instance of a class with the following public methods:
      getnchannels()  -- returns number of audio channels (1 for
                         mono, 2 for stereo)
      getsampwidth()  -- returns sample width in bytes
      getframerate()  -- returns sampling frequency
      getnframes()    -- returns number of audio frames
      getcomptype()   -- returns compression type ('NONE' for linear samples)
      getcompname()   -- returns human-readable version of
                         compression type ('not compressed' linear samples)
      getparams()     -- returns a namedtuple consisting of all of the
                         above in the above order
      getmarkers()    -- returns None (for compatibility with the
                         aifc module)
      getmark(id)     -- raises an error since the mark does not
                         exist (for compatibility with the aifc module)
      readframes(n)   -- returns at most n frames of audio
      rewind()        -- rewind to the beginning of the audio stream
      setpos(pos)     -- seek to the specified position
      tell()          -- return the current position
      close()         -- close the instance (make it unusable)
The position returned by tell() and the position given to setpos()
are compatible and have nothing to do with the actual position in the
file.
The close() method is called automatically when the class instance
is destroyed.
Writing WAVE files:
      f = wave.open(file, 'w')
where file is either the name of a file or an open file pointer.
The open file pointer must have methods write(), tell(), seek(), and
close().
This returns an instance of a class with the following public methods:
      setnchannels(n) -- set the number of channels
      setsampwidth(n) -- set the sample width
      setframerate(n) -- set the frame rate
      setnframes(n)   -- set the number of frames
      setcomptype(type, name)
                      -- set the compression type and the
                         human-readable compression type
      setparams(tuple)
                      -- set all parameters at once
      tell()          -- return current position in output file
      writeframesraw(data)
                      -- write audio frames without patching up the
                         file header
      writeframes(data)
                      -- write audio frames and patch up the file header
      close()         -- patch up the file header and close the
                         output file
You should set the parameters before the first writeframesraw or
writeframes.  The total number of frames does not need to be set,
but when it is set to the correct value, the header does not have to
be patched up.
It is best to first set all parameters, perhaps possibly the
compression type, and then write audio frames using writeframesraw.
When all frames have been written, either call writeframes(b'') or
close() to patch up the sizes in the header.
The close() method is called automatically when the class instance
is destroyed.
"""

from chunk import Chunk
from collections import namedtuple
import audioop
import builtins
import struct
import sys


__all__ = ["open", "Error", "Wave_read", "Wave_write"]

class Error(Exception):
    pass

WAVE_FORMAT_PCM = 0x0001

_array_fmts = None, 'b', 'h', None, 'i'

_wave_params = namedtuple('_wave_params',
                     'nchannels sampwidth framerate nframes comptype compname')

class Wave_read:
    """Variables used in this class:
    These variables are available to the user though appropriate
    methods of this class:
    _file -- the open file with methods read(), close(), and seek()
              set through the __init__() method
    _nchannels -- the number of audio channels
              available through the getnchannels() method
    _nframes -- the number of audio frames
              available through the getnframes() method
    _sampwidth -- the number of bytes per audio sample
              available through the getsampwidth() method
    _framerate -- the sampling frequency
              available through the getframerate() method
    _comptype -- the AIFF-C compression type ('NONE' if AIFF)
              available through the getcomptype() method
    _compname -- the human-readable AIFF-C compression type
              available through the getcomptype() method
    _soundpos -- the position in the audio stream
              available through the tell() method, set through the
              setpos() method
    These variables are used internally only:
    _fmt_chunk_read -- 1 iff the FMT chunk has been read
    _data_seek_needed -- 1 iff positioned correctly in audio
              file for readframes()
    _data_chunk -- instantiation of a chunk class for the DATA chunk
    _framesize -- size of one frame in the file
    """

    def initfp(self, file):
        self._convert = None
        self._soundpos = 0
        self._file = Chunk(file, bigendian = 0)
        if self._file.getname() != b'RIFF':
            raise Error('file does not start with RIFF id')
        if self._file.read(4) != b'WAVE':
            raise Error('not a WAVE file')
        self._fmt_chunk_read = 0
        self._data_chunk = None
        while 1:
            self._data_seek_needed = 1
            try:
                chunk = Chunk(self._file, bigendian = 0)
            except EOFError:
                break
            chunkname = chunk.getname()
            if chunkname == b'fmt ':
                self._read_fmt_chunk(chunk)
                self._fmt_chunk_read = 1
            elif chunkname == b'data':
                if not self._fmt_chunk_read:
                    raise Error('data chunk before fmt chunk')
                self._data_chunk = chunk
                self._nframes = chunk.chunksize // self._framesize
                self._data_seek_needed = 0
                break
            chunk.skip()
        if not self._fmt_chunk_read or not self._data_chunk:
            raise Error('fmt chunk and/or data chunk missing')

    def __init__(self, f):
        self._i_opened_the_file = None
        if isinstance(f, str):
            f = builtins.open(f, 'rb')
            self._i_opened_the_file = f
        # else, assume it is an open file object already
        try:
            self.initfp(f)
        except:
            if self._i_opened_the_file:
                f.close()
            raise

    def __del__(self):
        self.close()

    def __enter__(self):
        return self

    def __exit__(self, *args):
        self.close()

    #
    # User visible methods.
    #
    def getfp(self):
        return self._file

    def rewind(self):
        self._data_seek_needed = 1
        self._soundpos = 0

    def close(self):
        self._file = None
        file = self._i_opened_the_file
        if file:
            self._i_opened_the_file = None
            file.close()

    def tell(self):
        return self._soundpos

    def getnchannels(self):
        return self._nchannels

    def getnframes(self):
        return self._nframes

    def getsampwidth(self):
        return self._sampwidth

    def getframerate(self):
        return self._framerate

    def getcomptype(self):
        return self._comptype

    def getcompname(self):
        return self._compname

    def getparams(self):
        return _wave_params(self.getnchannels(), self.getsampwidth(),
                       self.getframerate(), self.getnframes(),
                       self.getcomptype(), self.getcompname())

    def getmarkers(self):
        return None

    def getmark(self, id):
        raise Error('no marks')

    def setpos(self, pos):
        if pos < 0 or pos > self._nframes:
            raise Error('position not in range')
        self._soundpos = pos
        self._data_seek_needed = 1

    def readframes(self, nframes):
        if self._data_seek_needed:
            self._data_chunk.seek(0, 0)
            pos = self._soundpos * self._framesize
            if pos:
                self._data_chunk.seek(pos, 0)
            self._data_seek_needed = 0
        if nframes == 0:
            return b''
        data = self._data_chunk.read(nframes * self._framesize)
        if self._sampwidth != 1 and sys.byteorder == 'big':
            data = audioop.byteswap(data, self._sampwidth)
        if self._convert and data:
            data = self._convert(data)
        self._soundpos = self._soundpos + len(data) // (self._nchannels * self._sampwidth)
        return data

    #
    # Internal methods.
    #

    def _read_fmt_chunk(self, chunk):
        try:
            wFormatTag, self._nchannels, self._framerate, dwAvgBytesPerSec, wBlockAlign = struct.unpack_from(', chunk.read(14))
        except struct.error:
            raise EOFError from None
        if wFormatTag == WAVE_FORMAT_PCM:
            try:
                sampwidth = struct.unpack_from(', chunk.read(2))[0]
            except struct.error:
                raise EOFError from None
            self._sampwidth = (sampwidth + 7) // 8
            if not self._sampwidth:
                raise Error('bad sample width')
        else:
            raise Error('unknown format: %r' % (wFormatTag,))
        if not self._nchannels:
            raise Error('bad # of channels')
        self._framesize = self._nchannels * self._sampwidth
        self._comptype = 'NONE'
        self._compname = 'not compressed'

class Wave_write:
    """Variables used in this class:
    These variables are user settable through appropriate methods
    of this class:
    _file -- the open file with methods write(), close(), tell(), seek()
              set through the __init__() method
    _comptype -- the AIFF-C compression type ('NONE' in AIFF)
              set through the setcomptype() or setparams() method
    _compname -- the human-readable AIFF-C compression type
              set through the setcomptype() or setparams() method
    _nchannels -- the number of audio channels
              set through the setnchannels() or setparams() method
    _sampwidth -- the number of bytes per audio sample
              set through the setsampwidth() or setparams() method
    _framerate -- the sampling frequency
              set through the setframerate() or setparams() method
    _nframes -- the number of audio frames written to the header
              set through the setnframes() or setparams() method
    These variables are used internally only:
    _datalength -- the size of the audio samples written to the header
    _nframeswritten -- the number of frames actually written
    _datawritten -- the size of the audio samples actually written
    """

    def __init__(self, f):
        self._i_opened_the_file = None
        if isinstance(f, str):
            f = builtins.open(f, 'wb')
            self._i_opened_the_file = f
        try:
            self.initfp(f)
        except:
            if self._i_opened_the_file:
                f.close()
            raise

    def initfp(self, file):
        self._file = file
        self._convert = None
        self._nchannels = 0
        self._sampwidth = 0
        self._framerate = 0
        self._nframes = 0
        self._nframeswritten = 0
        self._datawritten = 0
        self._datalength = 0
        self._headerwritten = False

    def __del__(self):
        self.close()

    def __enter__(self):
        return self

    def __exit__(self, *args):
        self.close()

    #
    # User visible methods.
    #
    def setnchannels(self, nchannels):
        if self._datawritten:
            raise Error('cannot change parameters after starting to write')
        if nchannels < 1:
            raise Error('bad # of channels')
        self._nchannels = nchannels

    def getnchannels(self):
        if not self._nchannels:
            raise Error('number of channels not set')
        return self._nchannels

    def setsampwidth(self, sampwidth):
        if self._datawritten:
            raise Error('cannot change parameters after starting to write')
        if sampwidth < 1 or sampwidth > 4:
            raise Error('bad sample width')
        self._sampwidth = sampwidth

    def getsampwidth(self):
        if not self._sampwidth:
            raise Error('sample width not set')
        return self._sampwidth

    def setframerate(self, framerate):
        if self._datawritten:
            raise Error('cannot change parameters after starting to write')
        if framerate <= 0:
            raise Error('bad frame rate')
        self._framerate = int(round(framerate))

    def getframerate(self):
        if not self._framerate:
            raise Error('frame rate not set')
        return self._framerate

    def setnframes(self, nframes):
        if self._datawritten:
            raise Error('cannot change parameters after starting to write')
        self._nframes = nframes

    def getnframes(self):
        return self._nframeswritten

    def setcomptype(self, comptype, compname):
        if self._datawritten:
            raise Error('cannot change parameters after starting to write')
        if comptype not in ('NONE',):
            raise Error('unsupported compression type')
        self._comptype = comptype
        self._compname = compname

    def getcomptype(self):
        return self._comptype

    def getcompname(self):
        return self._compname

    def setparams(self, params):
        nchannels, sampwidth, framerate, nframes, comptype, compname = params
        if self._datawritten:
            raise Error('cannot change parameters after starting to write')
        self.setnchannels(nchannels)
        self.setsampwidth(sampwidth)
        self.setframerate(framerate)
        self.setnframes(nframes)
        self.setcomptype(comptype, compname)

    def getparams(self):
        if not self._nchannels or not self._sampwidth or not self._framerate:
            raise Error('not all parameters set')
        return _wave_params(self._nchannels, self._sampwidth, self._framerate,
              self._nframes, self._comptype, self._compname)

    def setmark(self, id, pos, name):
        raise Error('setmark() not supported')

    def getmark(self, id):
        raise Error('no marks')

    def getmarkers(self):
        return None

    def tell(self):
        return self._nframeswritten

    def writeframesraw(self, data):
        if not isinstance(data, (bytes, bytearray)):
            data = memoryview(data).cast('B')
        self._ensure_header_written(len(data))
        nframes = len(data) // (self._sampwidth * self._nchannels)
        if self._convert:
            data = self._convert(data)
        if self._sampwidth != 1 and sys.byteorder == 'big':
            data = audioop.byteswap(data, self._sampwidth)
        self._file.write(data)
        self._datawritten += len(data)
        self._nframeswritten = self._nframeswritten + nframes

    def writeframes(self, data):
        self.writeframesraw(data)
        if self._datalength != self._datawritten:
            self._patchheader()

    def close(self):
        try:
            if self._file:
                self._ensure_header_written(0)
                if self._datalength != self._datawritten:
                    self._patchheader()
                self._file.flush()
        finally:
            self._file = None
            file = self._i_opened_the_file
            if file:
                self._i_opened_the_file = None
                file.close()

    #
    # Internal methods.
    #

    def _ensure_header_written(self, datasize):
        if not self._headerwritten:
            if not self._nchannels:
                raise Error('# channels not specified')
            if not self._sampwidth:
                raise Error('sample width not specified')
            if not self._framerate:
                raise Error('sampling rate not specified')
            self._write_header(datasize)

    def _write_header(self, initlength):
        assert not self._headerwritten
        self._file.write(b'RIFF')
        if not self._nframes:
            self._nframes = initlength // (self._nchannels * self._sampwidth)
        self._datalength = self._nframes * self._nchannels * self._sampwidth
        try:
            self._form_length_pos = self._file.tell()
        except (AttributeError, OSError):
            self._form_length_pos = None
        self._file.write(struct.pack(',
            36 + self._datalength, b'WAVE', b'fmt ', 16,
            WAVE_FORMAT_PCM, self._nchannels, self._framerate,
            self._nchannels * self._framerate * self._sampwidth,
            self._nchannels * self._sampwidth,
            self._sampwidth * 8, b'data'))
        if self._form_length_pos is not None:
            self._data_length_pos = self._file.tell()
        self._file.write(struct.pack(', self._datalength))
        self._headerwritten = True

    def _patchheader(self):
        assert self._headerwritten
        if self._datawritten == self._datalength:
            return
        curpos = self._file.tell()
        self._file.seek(self._form_length_pos, 0)
        self._file.write(struct.pack(', 36 + self._datawritten))
        self._file.seek(self._data_length_pos, 0)
        self._file.write(struct.pack(', self._datawritten))
        self._file.seek(curpos, 0)
        self._datalength = self._datawritten

def open(f, mode=None):
    if mode is None:
        if hasattr(f, 'mode'):
            mode = f.mode
        else:
            mode = 'rb'
    if mode in ('r', 'rb'):
        return Wave_read(f)
    elif mode in ('w', 'wb'):
        return Wave_write(f)
    else:
        raise Error("mode must be 'r', 'rb', 'w', or 'wb'")

参考：

1. wave — 读写WAV格式文件
2. python 3x - about writing with the python wave module