痞子衡嵌入式：语音处理工具pzh-speech诞生记（4）- 音频录播实现(PyAudio)

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　　大家好，我是痞子衡，是正经搞技术的痞子。今天痞子衡给大家介绍的是语音处理工具pzh-py-speech诞生之音频录播实现。

　　音频录播是pzh-py-speech的主要功能，pzh-py-speech借助的是Python自带wave库以及第三方PyAudio库来实现的音频播放和录制功能，今天痞子衡为大家介绍音频录播在pzh-py-speech中是如何实现的。

一、wave简介

　　wave是python标准库，其可以实现wav音频文件的读写，并且能解析wav音频的参数。pzh-py-speech借助wave库来读写wav文件，播放音频时借助wave库来读取wav文件并获取音频参数（通道，采样宽度，采样率），录制音频时借助wave库来设置音频参数并保存成wav文件。下面列举了pzh-py-speech所用到的全部API：

• wave用法: https://docs.python.org/2/library/wave.html

wave.open()

# wav音频读API
Wave_read.getnchannels()       # 获取音频通道数
Wave_read.getsampwidth()       # 获取音频采样宽度
Wave_read.getframerate()       # 获取音频采样率
Wave_read.getnframes()         # 获取音频总帧数
Wave_read.readframes(n)        # 读取音频帧数据
Wave_read.tell()               # 获取已读取的音频帧数
Wave_read.close()

# wav音频写API
Wave_write.setnchannels(n)     # 设置音频通道数
Wave_write.setsampwidth(n)     # 设置音频采样宽度
Wave_write.setframerate(n)     # 设置音频采样率
Wave_write.writeframes(data)   # 写入音频帧数据
Wave_write.close()

二、PyAudio简介

　　PyAudio是开源跨平台音频库PortAudio的python封装，PyAudio库的维护者是Hubert Pham，该库从2006年开始推出，一直持续更新至今，pzh-py-speech使用的是PyAudio 0.2.11。
　　pzh-py-speech借助PyAudio库来实现音频数据流控制（包括从PC麦克风获取音频流，将音频流输出给PC扬声器），如果说wave库实现的是对wav文件的单纯操作，那么PyAudio库则实现的是音频相关硬件设备的交互。
　　PyAudio项目的官方主页如下：

• PortAudio官方主页: http://www.portaudio.com/
  
• PyAudio官方主页: http://people.csail.mit.edu/hubert/pyaudio/
  
• PyAudio安装方法: https://pypi.org/project/PyAudio/

　　PyAudio对音频流的控制有两种，一种是阻塞式的，另一种是非阻塞式的(callback)，前者一般用于确定的音频控制（比如单纯播放一个本地音频文件，并且中途不会有暂停/继续等操作），后者一般用于灵活的音频控制（比如录制一段音频，但是要等待一个事件响应才会结束）。pzh-py-speech用的是后者。下面是两种方式的音频播放使用示例：

import pyaudio
import wave

CHUNK = 1024

wf = wave.open(“test.wav”, 'rb')
p = pyaudio.PyAudio()

##########################################################
# 此为阻塞式，循环读取1024个byte音频数据去播放，直到test.wav文件数据被全部读出
stream = p.open(format=p.get_format_from_width(wf.getsampwidth()),
                channels=wf.getnchannels(),
                rate=wf.getframerate(),
                output=True)
data = wf.readframes(CHUNK)
while data != '':
    stream.write(data)
    data = wf.readframes(CHUNK)
##########################################################
# 此为非阻塞式的(callback)，系统会自动读取test.wav文件里的音频帧，直到播放完毕
def callback(in_data, frame_count, time_info, status):
    data = wf.readframes(frame_count)
    return (data, pyaudio.paContinue)
stream = p.open(format=p.get_format_from_width(wf.getsampwidth()),
                channels=wf.getnchannels(),
                rate=wf.getframerate(),
                output=True,
                stream_callback=callback)
stream.start_stream()
while stream.is_active():
    time.sleep(0.1)
##########################################################

stream.stop_stream()
stream.close()
p.terminate()

三、pzh-py-speech音频录播实现

3.1 播放实现

　　播放功能本身实现不算复杂，但pzh-py-speech里实现的是播放按钮的五种状态Start -> Play -> Pause -> Resume -> End控制，即播放中途实现了暂停和恢复，因此代码要稍微复杂一些。此处的重点是playAudioCallback()函数里的else分支，如果在暂停状态下，必须还是要给PyAudio返回一段空数据：

import wave
import pyaudio

AUDIO_PLAY_STATE_START = 0
AUDIO_PLAY_STATE_PLAY = 1
AUDIO_PLAY_STATE_PAUSE = 2
AUDIO_PLAY_STATE_RESUME = 3
AUDIO_PLAY_STATE_END = 4

class mainWin(win.speech_win):

    def __init__(self, parent):
        # ...
        # Start -> Play -> Pause -> Resume -> End
        self.playState = AUDIO_PLAY_STATE_START

    def viewAudio( self, event ):
        self.wavPath =  self.m_genericDirCtrl_audioDir.GetFilePath()
        if self.playState != AUDIO_PLAY_STATE_START:
            self.playState = AUDIO_PLAY_STATE_END
            self.m_button_play.SetLabel('Play Start')

    def playAudioCallback(self, in_data, frame_count, time_info, status):
        if self.playState == AUDIO_PLAY_STATE_PLAY or self.playState == AUDIO_PLAY_STATE_RESUME:
            data = self.wavFile.readframes(frame_count)
            if self.wavFile.getnframes() == self.wavFile.tell():
                status = pyaudio.paComplete
                self.playState = AUDIO_PLAY_STATE_END
                self.m_button_play.SetLabel('Play Start')
            else:
                status = pyaudio.paContinue
            return (data, status)
        else:
            # Note!!!:
            data = numpy.zeros(frame_count*self.wavFile.getnchannels()).tostring()
            return (data, pyaudio.paContinue)

    def playAudio( self, event ):
        if os.path.isfile(self.wavPath):
            if self.playState == AUDIO_PLAY_STATE_END:
                self.playState = AUDIO_PLAY_STATE_START
                self.wavStream.stop_stream()
                self.wavStream.close()
                self.wavPyaudio.terminate()
                self.wavFile.close()
            if self.playState == AUDIO_PLAY_STATE_START:
                self.playState = AUDIO_PLAY_STATE_PLAY
                self.m_button_play.SetLabel('Play Pause')
                self.wavFile =  wave.open(self.wavPath, "rb")
                self.wavPyaudio = pyaudio.PyAudio()
                self.wavStream = self.wavPyaudio.open(format=self.wavPyaudio.get_format_from_width(self.wavFile.getsampwidth()),
                                                      channels=self.wavFile.getnchannels(),
                                                      rate=self.wavFile.getframerate(),
                                                      output=True,
                                                      stream_callback=self.playAudioCallback)
                self.wavStream.start_stream()
            elif self.playState == AUDIO_PLAY_STATE_PLAY or self.playState == AUDIO_PLAY_STATE_RESUME:
                self.playState = AUDIO_PLAY_STATE_PAUSE
                self.m_button_play.SetLabel('Play Resume')
            elif self.playState == AUDIO_PLAY_STATE_PAUSE:
                self.playState = AUDIO_PLAY_STATE_RESUME
                self.m_button_play.SetLabel('Play Pause')
            else:
                pass

3.2 录制实现

　　相比播放功能，录制功能就简单了些，因为录制按钮状态就两种Start -> End，暂不支持中断后继续录制。这里的重点主要是音频三大参数（采样宽度，采样率，通道数）设置的支持：

import wave
import pyaudio

class mainWin(win.speech_win):

    def recordAudioCallback(self, in_data, frame_count, time_info, status):
        if not self.isRecording:
            status = pyaudio.paComplete
        else:
            self.wavFrames.append(in_data)
            status = pyaudio.paContinue
        return (in_data, status)

    def recordAudio( self, event ):
        if not self.isRecording:
            self.isRecording = True
            self.m_button_record.SetLabel('Record Stop')
            # Get the wave parameter from user settings
            fileName = self.m_textCtrl_recFileName.GetLineText(0)
            if fileName == '':
                fileName = 'rec_untitled1.wav'
            self.wavPath = os.path.join(os.path.dirname(os.path.abspath(os.path.dirname(__file__))), 'conv', 'rec', fileName)
            self.wavSampRate = int(self.m_choice_sampRate.GetString(self.m_choice_sampRate.GetSelection()))
            channels = self.m_choice_channels.GetString(self.m_choice_channels.GetSelection())
            if channels == 'Mono':
                self.wavChannels = 1
            else: #if channels == 'Stereo':
                self.wavChannels = 2
            bitDepth = int(self.m_choice_bitDepth.GetString(self.m_choice_bitDepth.GetSelection()))
            if bitDepth == 8:
                self.wavBitFormat = pyaudio.paInt8
            elif bitDepth == 24:
                self.wavBitFormat = pyaudio.paInt24
            elif bitDepth == 32:
                self.wavBitFormat = pyaudio.paFloat32
            else:
                self.wavBitFormat = pyaudio.paInt16
            # Record audio according to wave parameters
            self.wavFrames = []
            self.wavPyaudio = pyaudio.PyAudio()
            self.wavStream = self.wavPyaudio.open(format=self.wavBitFormat,
                                                  channels=self.wavChannels,
                                                  rate=self.wavSampRate,
                                                  input=True,
                                                  frames_per_buffer=AUDIO_CHUNK_SIZE,
                                                  stream_callback=self.recordAudioCallback)
            self.wavStream.start_stream()
        else:
            self.isRecording = False
            self.m_button_record.SetLabel('Record Start')
            self.wavStream.stop_stream()
            self.wavStream.close()
            self.wavPyaudio.terminate()
            # Save the wave data into file
            wavFile = wave.open(self.wavPath, 'wb')
            wavFile.setnchannels(self.wavChannels)
            wavFile.setsampwidth(self.wavPyaudio.get_sample_size(self.wavBitFormat))
            wavFile.setframerate(self.wavSampRate)
            wavFile.writeframes(b''.join(self.wavFrames))
            wavFile.close()

　　至此，语音处理工具pzh-py-speech诞生之音频录播实现痞子衡便介绍完毕了，掌声在哪里~~~

参考文档

1. Python解析Wav文件并绘制波形的方法