portaudio pa_devs report 0 device - portaudio

Question

My system is ubuntu 15.10. I am very sure my audio works,
arecord -l
**** List of CAPTURE Hardware Devices ****
card 1: PCH [HDA Intel PCH], device 0: ALC887-VD Analog [ALC887-VD Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 2: ALC887-VD Alt Analog [ALC887-VD Alt Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
but pa_devs, which is a official provided execuatble file in portaudio, reports 0 device as below,
PortAudio version number = 1899
PortAudio version text = 'PortAudio V19-devel (built Jan 30 2016 19:22:45)'
Number of devices = 0
And I can get devices number with pyAudio
import pyaudio
pa = pyaudio.PyAudio()
print(pa.get_default_input_device_info())
print(pa.get_device_count())
--- output ---
{'defaultHighInputLatency': 0.034829931972789115, 'maxInputChannels': 32, 'defaultLowOutputLatency': 0.008707482993197279, 'defaultLowInputLatency': 0.008707482993197279, 'defaultSampleRate': 44100.0, 'hostApi': 0, 'structVersion': 2, 'maxOutputChannels': 32, 'defaultHighOutputLatency': 0.034829931972789115, 'name': 'default', 'index': 6}
7
Should I install something or re-built portaudio with some special settings? Thanks!

Answer 1

I ran into this exact same problem. It was because portaudio was built with only support for OSS. You need to build it with ALSA support. Note that even if you specify --with-alsa to the ./configure script it still "succeeds" even if it can't find ALSA - you have to manually check the configuration summary for a line like this:
ALSA ........................ no
(Don't you love autotools?)
Anyway do this:
sudo apt-get install libasound2-dev
./configure
And so on. I unfortunately couldn't find a way to get pa_devs to list what backends it supports, so you just have to guess this is the problem and try it. Worked for me anyway!