python - PyAudio 工作，但每次都吐出错误消息

Question

我正在使用 PyAudio 记录麦克风的输入。

既然音频对我来说录制得很好，我应该尝试简单地抑制它的错误消息吗？或者有办法解决吗？

ALSA lib pcm.c:2212:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2212:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2212:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib audio/pcm_bluetooth.c:1613:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib audio/pcm_bluetooth.c:1613:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib audio/pcm_bluetooth.c:1613:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib audio/pcm_bluetooth.c:1613:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib pcm_dmix.c:957:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave
Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started

Answer 1

您可以尝试清理您的 ALSA 配置，例如，

ALSA lib pcm.c:2212:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2212:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2212:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side

是由/usr/share/alsa/alsa.conf引起的:

pcm.rear cards.pcm.rear
pcm.center_lfe cards.pcm.center_lfe
pcm.side cards.pcm.side

一旦你注释掉这些行，那些错误信息就会消失。您可能还需要检查 ~/.asoundrc 和 /etc/asound.conf。

也就是说，其中一些消息表明您的配置有问题，尽管它们不会导致任何真正的问题。我不建议你清理 alsa.conf，因为它最初来自 ALSA，当你更新 alsa-lib 时可能会被覆盖。

在 Python 中有一种抑制消息的方法，这里是一个示例代码:

#!/usr/bin/env python
from ctypes import *
import pyaudio

# From alsa-lib Git 3fd4ab9be0db7c7430ebd258f2717a976381715d
# $ grep -rn snd_lib_error_handler_t
# include/error.h:59:typedef void (*snd_lib_error_handler_t)(const char *file, int line, const char *function, int err, const char *fmt, ...) /* __attribute__ ((format (printf, 5, 6))) */;
# Define our error handler type
ERROR_HANDLER_FUNC = CFUNCTYPE(None, c_char_p, c_int, c_char_p, c_int, c_char_p)
def py_error_handler(filename, line, function, err, fmt):
  print 'messages are yummy'
c_error_handler = ERROR_HANDLER_FUNC(py_error_handler)

asound = cdll.LoadLibrary('libasound.so')
# Set error handler
asound.snd_lib_error_set_handler(c_error_handler)
# Initialize PyAudio
p = pyaudio.PyAudio()
p.terminate()

print '-'*40
# Reset to default error handler
asound.snd_lib_error_set_handler(None)
# Re-initialize
p = pyaudio.PyAudio()
p.terminate()

我电脑的输出:

messages are yummy
messages are yummy
messages are yummy
messages are yummy
messages are yummy
messages are yummy
----------------------------------------
ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_dmix.c:957:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave

这些消息是由 alsa-lib 打印出来的，而不是 PyAudio 或 PortAudio。该代码直接使用 alsa-lib snd_lib_error_set_handler 函数设置错误处理程序 py_error_handler，您可以使用它来丢弃任何消息。

我检查了其他 Python ALSA 绑定(bind)，pyalsa 和 PyAlsaAudio，它们不支持设置错误处理程序。但是，有 an issue在 PortAudio 上，之前似乎所有 ALSA 错误消息都被抑制了。