PyAudio抛出“无法打开从属”错误

Question

嗨，每次执行pyauido.PyAudio（）时，我都会遇到以下错误。 我尝试使用以下说明显示麦克风录制的音频：https://swharden.com/wp/2016-07-19-realtime-audio-visualization-in-python/ 使用我的USB麦克风和raspberry pi 3+的耳机插孔

Expression 'alsa_snd_pcm_hw_params_set_period_size_near( pcm, hwParams, &alsaPer                                  iodFrames, &dir )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 924
Expression 'alsa_snd_pcm_hw_params_set_period_size_near( pcm, hwParams, &alsaPer                                   iodFrames, &dir )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 924
ALSA lib pcm_dmix.c:1108:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.hdmi
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.hdmi
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline
ALSA lib pcm.c:2565:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline
ALSA lib pcm_dmix.c:1108:(snd_pcm_dmix_open) unable to open slave
Expression 'alsa_snd_pcm_hw_params_set_period_size_near( pcm, hwParams, &alsaPer                                   iodFrames, &dir )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 924 

更新：如评论中所述，我通过编辑alsa.conf文件摆脱了“未知PCM”，但我意识到回溯并没有添加到我在这里发布的代码片段中，因此这里是“新的，完整的”-消息：

Expression 'alsa_snd_pcm_hw_params_set_period_size_near( pcm, hwParams, &alsaPeriodFrames, &dir )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 924
ALSA lib pcm_dsnoop.c:638:(snd_pcm_dsnoop_open) unable to open slave
ALSA lib pcm_dmix.c:1108:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm_dmix.c:1108:(snd_pcm_dmix_open) unable to open slave
Expression 'alsa_snd_pcm_hw_params_set_period_size_near( pcm, hwParams, &alsaPeriodFrames, &dir )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 924
Traceback (most recent call last):
  File "sound.py", line 9, in <module>
    frames_per_buffer=CHUNK)
  File "/usr/lib/python2.7/dist-packages/pyaudio.py", line 750, in open
    stream = Stream(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/pyaudio.py", line 441, in __init__
    self._stream = pa.open(**arguments)
IOError: [Errno -9996] Invalid input device (no default output device)

其他信息：

**** List of CAPTURE Hardware Devices ****
card 2: Device [USB PnP Audio Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

[12:06:02] openhabian@openhab:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: b1 [bcm2835 HDMI 1], device 0: bcm2835 HDMI 1 [bcm2835 HDMI 1]
  Subdevices: 4/4
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
card 1: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones]
  Subdevices: 4/4
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3

.asoundrc-配置：

pcm.!default {
  type asym
  capture.pcm "hw:2,0"
  playback.pcm "hw:1,0"
}

Answer 1

如果有其他人出现此问题，至少有一个解决方案可用于删除“未知…”-消息：

PyAudio working, but spits out error messages each time