Finding all the devices I can use to play PCM with ALSA - linux

Question

I use ALSA to play PCM samples. I open the PCM stream with this function:
int snd_pcm_open(snd_pcm_t** pcmp,
const char* name,
snd_pcm_stream_t stream,
int mode);
I'm currently using "default" as the name parameter. I would like to be able to choose other devices. What I cannot understand is how I can determine what are the names of the other available devices.
I attached a USB microphone to my system and aplay and amixer seems to detect the new device. How do I determine the name of that device? Is there any ALSA function to get a list of available devices with their respective names?

Answer 1

I think you can use snd_device_name_hint for enumerating devices.
Here is an example. Beware that I haven't compiled it !
char **hints;
/* Enumerate sound devices */
int err = snd_device_name_hint(-1, "pcm", (void***)&hints);
if (err != 0)
return;//Error! Just return
char** n = hints;
while (*n != NULL) {
char *name = snd_device_name_get_hint(*n, "NAME");
if (name != NULL && 0 != strcmp("null", name)) {
//Copy name to another buffer and then free it
free(name);
}
n++;
}//End of while
//Free hint buffer too
snd_device_name_free_hint((void**)hints);

Answer 2

It was my first requirements to a linux/unix projects where I need to know about all of the available audio devices capability and name. Then I need to use these devices to capture and plaback 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 programme 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#~]# ./IdeaAudioEngineTest
HDA Intel plughw:0,0
HDA Intel plughw:0,2
USB Audio Device plughw:1,0
This library can also capture and playback the real-time audio data.
It is available with documentation in IdeaAudio library with Duplex Alsa Audio

Answer 3

Just for grins, your program reformatted:
#include <stdio.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <alsa/asoundlib.h>
void listdev(char *devname)
{
char** hints;
int err;
char** n;
char* name;
char* desc;
char* ioid;
/* Enumerate sound devices */
err = snd_device_name_hint(-1, devname, (void***)&hints);
if (err != 0) {
fprintf(stderr, "*** Cannot get device names\n");
exit(1);
}
n = hints;
while (*n != NULL) {
name = snd_device_name_get_hint(*n, "NAME");
desc = snd_device_name_get_hint(*n, "DESC");
ioid = snd_device_name_get_hint(*n, "IOID");
printf("Name of device: %s\n", name);
printf("Description of device: %s\n", desc);
printf("I/O type of device: %s\n", ioid);
printf("\n");
if (name && strcmp("null", name)) free(name);
if (desc && strcmp("null", desc)) free(desc);
if (ioid && strcmp("null", ioid)) free(ioid);
n++;
}
//Free hint buffer too
snd_device_name_free_hint((void**)hints);
}
int main(void)
{
printf("PCM devices:\n");
printf("\n");
listdev("pcm");
printf("MIDI devices:\n");
printf("\n");
listdev("rawmidi");
return 0;
}