How to find out ALSA audio device capabilities programmatically in Linux without opening the device

Use snd_ctl_next to iterate over all devices, then snd_ctl_open to get info about the device - this is not the same as snd_pcm_open, which could fail if another program has the device open or if you have bad settings.

It's quite dense, but here's some open-source code that iterates over all ALSA devices you could look at: https://app.assembla.com/spaces/portaudio/git/source/master/src/hostapi/alsa/pa_linux_alsa.c - search for BuildDeviceList to get started.

It was my first requirements to a linux/unix projects where I need to know about all of the available audio devices capability. Then I need to use these devices to capture and playback the audio. What I have done is pretty simple. There is a linux/unix command which is used to find the devices through alsa utility in linux.

It is:

aplay -l

Now what I did is just make a program to give the out as like as this by alsa.

For everyone's help I have made a (.so) library and a sample Application demonstrating the use of this library in c++.

The output of my library is like-

[root@~]# ./IdeaAudioEngineTestHDA Intel plughw:0,0HDA Intel plughw:0,2

This library can also capture and playback the real-time audio data.

It is available with documentation in IdeaAudio library with Duplex Alsa Audio

No, there is no other way to query number of channels, sample rate etc. other than opening the card with snd_pcm_open.