最近使用Python的Struct Unpack遇到的问题

问题描述 投票:0回答:1

[在Python脚本中,我使用以下命令录制一些音频:

import subprocess
import wave
self.rec_args =['arecord', '--device=pulse', '-f', 'cd', '-t', '/home/USER/audioFile.wav')]
self.rec = subprocess.Popen(self.rec_args, shell=False)

然后我打开文件:

self.wave_file = wave.open('/home/USER/audioFile.wav', 'rb')

并通过以下方式获得通道数(2)和采样率(44100):

self.num_channels, self.sample_rate = self.getWaveParameters(self.wave_file)

然后我可以使用getWaveIntegers的代码来获取声音的振幅:

wi = self.getWaveIntegers(self.wave_file, self.sample_rate, self.num_channels, 0, 20)

其中clipStart = 0,然后要分析的样本长度= 20秒。

########################################
    def getWaveIntegers(self, stream, sample_rate, num_channels, clipStart, timeLength):
# https://stackoverflow.com/questions/2226853/
# stream = the already opened wave file to navigate through
# clipStart = the starting position of the clip in the wave file
# timeLength = the length of time of the clip to take from the wave file
# set start of clip
        startPosition = sample_rate * clipStart # converts clipStart time to samplewidth
        stream.setpos(startPosition) # set the starting position in the wave file
# length of clip
        clipLength = sample_rate*timeLength*num_channels # timeLength in terms of channels and sample rate ####?
        clipData = stream.readframes(sample_rate*timeLength) # the clip of the wave file starting at startPosition for time in sample_rate
        integer_data = wave.struct.unpack("%dh"%(clipLength), clipData)
        channels = [ [] for time in range(num_channels) ]
        for index, value in enumerate(integer_data):
            bucket = index % num_channels
            channels[bucket].append(value)
        del clipData
# keep only left? channel
        sampleChannel = []
        for c in range(0, len(channels[0]):
           sampleChannel.append(abs(int(channels[0][c]/100)))
        return sampleChannel
########################################
    def getWaveParameters(self, stream):
# https://stackoverflow.com/questions/2226853/
        num_channels = stream.getnchannels()
        sample_rate = stream.getframerate()
        sample_width = stream.getsampwidth()
        num_frames = stream.getnframes()
        raw_data = stream.readframes( num_frames ) # Returns byte data
        total_samples = num_frames * num_channels
        if sample_width == 1: 
            fmt = "%iB" % total_samples # read unsigned chars
        elif sample_width == 2:
            fmt = "%ih" % total_samples # read signed 2 byte shorts
        else:
            raise ValueError("Only supports 8 and 16 bit audio formats.")
        return num_channels, sample_rate#, sample_width, num_frames, total_samples, fmt # do not need these values for this code
########################################

直到最近,它一直可以正常工作。我现在收到以下错误:

Traceback (most recent call last):
  File "myfile.py", line 167, in getWaveIntegers
    integer_data = wave.struct.unpack("%dh"%(clipLength), clipData)
struct.error: unpack requires a buffer of 3528000 bytes

某些文件的clipLength似乎是:1764000字节(恰好是错误中3528000字节的一半)

[我注意到过去几天中各种Python库已更新为以下版本:Python 3.6:amd64(3.6.8-1〜18.04.3,3.6.9-1〜18.04)

我尝试了https://docs.python.org/3.6/library/struct.html上的示例

>>> from struct import *
>>> pack('hhl', 1, 2, 3)
b'\x00\x01\x00\x02\x00\x00\x00\x03'
>>> unpack('hhl', b'\x00\x01\x00\x02\x00\x00\x00\x03')
(1, 2, 3)

当我在系统上执行此操作时(Python 3.6.9(默认值,Nov 7 2019,10:44:02)和Linux上的[GCC 8.3.0]:]]

>>> from struct import *
>>> pack('hhl', 1, 2, 3)
b'\x01\x00\x02\x00\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00'

长度是示例中长度的两倍。使用:

>>> unpack('hhl', b'\x00\x01\x00\x02\x00\x00\x00\x03')

我收到错误:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
struct.error: unpack requires a buffer of 16 bytes

但是当我这样做时:

>>> unpack('hhl', b'\x01\x00\x02\x00\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00')
(1, 2, 3)

我得到正确的答案。

我做了些奇怪的事情,还是Python更新中的错误?老实说,我没有完全理解struct命令。非常感谢您阅读像我这样的挡风玻璃上的贴子!约翰

在Python脚本中,我使用以下命令录制一些音频:import子进程import wave self.rec_args = ['arecord','--device = pulse','-f','cd','-t', '/home/USER/audioFile.wav')] ...

python struct unpack
1个回答
0
投票

如上所述,我无法弄清struct unpack的问题,所以我围绕它进行了编程并使用了numpy。因此,getWaveIntegers的代码应为:

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