play multiple wav files simultaneously using alsa c api

Question

I want to implement a specific functionality to my project which includes continuously playing a sample-default.wav in the background and play a sample-specific.wav file when some specific condition matches. What I really want is that, when sample-specific.wav file is running, volume of sample-default.wav file becomes 0 (or simply, I want to mute sample-default.wav file when sample-specific.wav is running).

I am trying to implement this functionality using alsa-library for c. I have tried almost every approach to achieve this but nothing seems to works for me.

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My current approach

I am trying to add two virtual sound devices using dmix plugin of alsa leaving default for system sounds. I searched google and find that I need to edit /etc/asound.conf file for creating different sound devices.

I added two sound devices, named notification and sample-sound. My current /etc/asound.conf file looks something like the one below:-

pcm.notification {
    type dmix
    ipc_key 1024
    slave {
        pcm "hw:1,0"
    }
}

ctl.notification {
     type hw
     card 2
}

pcm.sample-sound {
     type dmix
     ipc_key 1025
    slave {
         pcm "hw:1,0"
    }
}

ctl.sample-sound {
     type hw
    card 3
}

This works perfectly fine with aplay i.e. when I am playing sample-default.wav file using aplay by the following command:-

aplay -D plug:notification sample-default.wav

It works, but when i am trying to run the following code to play sample-default.wav using alsa library on my notification device:-

#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>
#include <pthread.h>

void default_sound (char * str) {
    snd_pcm_t *handle;
    snd_pcm_hw_params_t *params;
    snd_pcm_uframes_t frames;

    /* Open PCM device for playback */
    int status = snd_pcm_open(&handle, "notification", SND_PCM_STREAM_PLAYBACK, 0);
    if (status < 0) {
        printf("Unable to open pcm deveice%s\n", snd_strerror(status));
        return;
    }

    /* Allocate a hardware parameter obejct */
    snd_pcm_hw_params_alloca(&params);

    /* Fill it with default values */
    snd_pcm_hw_params_any(handle, params);

    /* Set the desired hardware parameters */

    /* Interleaved mode */
    snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);

    /* Signed 16-bit little-endian format */
    snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);

    /* Single Channel (mono) */
    snd_pcm_hw_params_set_channels(handle, params, 1);

    /* sampling rate */
    unsigned int sample_rate = 16000;
    int dir;
    snd_pcm_hw_params_set_rate_near(handle, params, &sample_rate, &dir);

    /* set period size to 32 frames */
    frames = 32;
    snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);

    /* Write the parameters to the driver */
    status = snd_pcm_hw_params(handle, params);
    if(status < 0) {
        printf("Unable to set hw params: %s\n", snd_strerror(status));
        return;
    }

    /* Use a buffer large enough to hold one period */
    snd_pcm_hw_params_get_period_size(params, &frames, &dir);

    int size = frames * 2;
    char *buffer = (char *)malloc(size);

    int readfd = open("sample-call.wav", O_RDONLY);
    if(readfd < 0) {
        printf("Error in opening wav file\n");
        exit(1);
    }


    int readval;
    while(readval = read(readfd, buffer, size) > 0) {
        status = snd_pcm_writei(handle, buffer, frames);
        if(status == -EPIPE) {
            printf("underrun occured\n");
            snd_pcm_prepare(handle);
        }
        else if(status < 0) {
            printf("Error from writei: %s\n", snd_strerror(status));
        }
    }

    snd_pcm_drain(handle);
    snd_pcm_close(handle);
    free(buffer);
}

int main() {
    pthread_t pthread_id;
    int status = pthread_create(&pthread_id, NULL, default_sound, "running");
    if (status != 0) {
        printf("Error in creating thread\n");
    }
    pthread_join(pthread_id, NULL);

    return 0;
}

It compiles successfully but throws run-time error :-

8211 segmentation fault (core dumped)  ./play-multiple-sound

I don't know what's going wrong with the above code.

If the above code works fine then I will play two sound files on two devices (notification and sample-sound) and control the volume of these devices using the alsa-mixer library which I have already implemented.

I am trying to achieve this from the past few weeks and none of the solution seems to work for me, so please help me out with this and if you know a better approach then please suggest.

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