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我正在尝试让 PyAudio 在我的 Raspberry Pi 3 上运行 SDR (rtl_fm) 并从耳机插孔播放音频。除了 USB SDR 作为源 fm 音频外，我没有其他任何东西，其他一切都是库存。

我已经通过他们的网站按照有关如何安装和设置 PyAudio 的说明进行操作。（https://people.csail.mit.edu/hubert/pyaudio/）

这是我当前的测试代码：

import pyaudio
import subprocess

CHUNK = 1024
WIDTH = 2
CHANNELS = 2
RATE = 44100
RECORD_SECONDS = 5

pipe1a = subprocess.Popen(['rtl_fm', '-f92.5M', '-Mfm', '-s170k', '-Afast', '-l0', '-Edeemp'], stdout=subprocess.PIPE)
pipe1b = subprocess.Popen(['play', '-r170k', '-traw', '-es', '-b16', '-c1', '-V1', '-'], stdin=pipe1a.stdout, stdout=subprocess.PIPE)

p = pyaudio.PyAudio()

stream = p.open(format=p.get_format_from_width(WIDTH),
            channels=CHANNELS,
            rate=RATE,
            input=True,
            output=True,
            frames_per_buffer=CHUNK)

print("* recording")

for i in range(0, int(RATE / CHUNK * RECORD_SECONDS)):
    data = stream.read(CHUNK)
    stream.write(data, CHUNK)

print("* done")

stream.stop_stream()
stream.close()

它尝试执行，我收到此错误：

>> python pyaudio_test_1.py
Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Generic RTL2832U OEM
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.front
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround21
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround21
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround40
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround41
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround50
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround51
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround71
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.iec958
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.iec958
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.iec958
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.hdmi
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.hdmi
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline
ALSA lib pulse.c:243:(pulse_connect) PulseAudio: Unable to connect: Connection refused

ALSA lib pulse.c:243:(pulse_connect) PulseAudio: Unable to connect: Connection refused

Traceback (most recent call last):
  File "pyaudio_test_1.py", line 28, in <module>
    frames_per_buffer=CHUNK)
  File "/usr/lib/python2.7/dist-packages/pyaudio.py", line 747, in open
    stream = Stream(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/pyaudio.py", line 442, in __init__
    self._stream = pa.open(**arguments)
IOError: [Errno Invalid input device (no default output device)] -9996
pi@raspberrypi:~/pyaudio_test $ Found Rafael Micro R820T tuner
Tuner gain set to automatic.
Tuned to 92755000 Hz.
Oversampling input by: 6x.
Oversampling output by: 1x.
Buffer size: 8.03ms
Exact sample rate is: 1020000.026345 Hz
Sampling at 1020000 S/s.
Output at 170000 Hz.
Signal caught, exiting!

User cancel, exiting...

我不知道如何处理 IOError。

我还认为 rtl_fm 和 pyaudio 设置可能存在设置不匹配，但我还是新手，不知道我在哪里不匹配，因为命名法略有不同。

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