test application

/*
 *  This extra small demo sends a random samples to your speakers.
 */

#include <alsa/asoundlib.h>
#include <unistd.h>

static char *device = "MEDIA_playback_0";           /* playback device */

static snd_pcm_uframes_t last_size = 20; /* Will be modifed by gdb */

snd_output_t *output = NULL;
unsigned char buffer[2*8*1024];              /* some random data */
unsigned char last_buff[4096*2];

int main(void)
{
    int err;
    unsigned int i;
    snd_pcm_t *handle;
    snd_pcm_sframes_t frames;
    static snd_output_t *output = NULL;
    long a, b, c;

    snd_pcm_hw_params_t *hwparams;
    snd_pcm_sw_params_t *swparams;

    err = snd_output_stdio_attach(&output, stdout, 0);
    if (err < 0) {
        printf("Output failed: %s\n", snd_strerror(err));
        return 0;
    }

    for (i = 0; i < sizeof(buffer); i++)
            buffer[i] = random() & 0xff;

    for (i = 0; i < sizeof(last_buff); i++)
        last_buff[i] = random() & 0xff;

    if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
        printf("Playback open error: %s\n", snd_strerror(err));
        exit(EXIT_FAILURE);
    }

    err = snd_pcm_hw_params_malloc(&hwparams);
    if (err < 0)
        goto exit;

    err = snd_pcm_hw_params_any(handle, hwparams);
        if (err < 0)
        goto exit;
    err = snd_pcm_hw_params_set_access(handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
        if (err < 0)
        goto exit;
    err = snd_pcm_hw_params_set_format(handle, hwparams, SND_PCM_FORMAT_S16_LE);
    //err = snd_pcm_hw_params_set_format(handle, hwparams, SND_PCM_FORMAT_U8);
        if (err < 0)
        goto exit;
    err = snd_pcm_hw_params_set_channels(handle, hwparams, 1);
        if (err < 0)
        goto exit;
    unsigned int rate = 18900;
    err = snd_pcm_hw_params_set_rate_near(handle, hwparams, &rate, 0);
        if (err < 0)
        goto exit;
    snd_pcm_uframes_t  size = 1024;
    err = snd_pcm_hw_params_set_period_size_near(handle, hwparams, &size, 0);
        if (err < 0)
        goto exit;
    snd_pcm_uframes_t  buffer2 = 16384;
    err = snd_pcm_hw_params_set_buffer_size_near(handle, hwparams, &buffer2);
        if (err < 0)
        goto exit;
    err = snd_pcm_hw_params(handle, hwparams);
        if (err < 0)
        goto exit;
    snd_pcm_hw_params_free(hwparams);

    err = snd_pcm_sw_params_malloc(&swparams);
        if (err < 0)
        goto exit;
    err = snd_pcm_sw_params_current(handle, swparams);
        if (err < 0)
        goto exit;
    err = snd_pcm_sw_params(handle, swparams);
        if (err < 0)
        goto exit;
    snd_pcm_sw_params_free(swparams);

    snd_pcm_dump(handle, output);

// (3) PREPARE
    err = snd_pcm_prepare(handle);
        if (err < 0)
        goto exit;

    a = snd_pcm_avail(handle);
    printf("a: %ld\n", a);

// (4) Start playback

    b = snd_pcm_avail_update(handle);
    printf("b: %ld\n", b);

    for (i = 0; i < 64; i++) {
        usleep(50000);
        b = snd_pcm_avail_update(handle);
        if( b > 1024 ) {
            frames = snd_pcm_writei(handle, buffer, size);
            if (frames < 0)
                frames = snd_pcm_recover(handle, frames, 0);
            if (frames < 0) {
                printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
                break;
            }
            if (frames > 0 && frames < (long)sizeof(buffer))
                printf("Short write (expected %li, wrote %li), c:%ld\n", (long)sizeof(buffer), frames, (a-b));
        }
    }

// LAST WRITE - NOT COMPLETE

    printf("frames: %ld, sizeof(buffer): %d\n", (long int)frames, sizeof(last_buff));
    frames = snd_pcm_writei(handle, last_buff, last_size);
    if (frames < 0)
        frames = snd_pcm_recover(handle, frames, 0);
    if (frames < 0) {
        printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
    }
    if (frames > 0 && frames < (long)sizeof(last_buff))
        printf("Short write (expected %li, wrote %li)\n", (long)sizeof(last_buff), frames);

// check buffer fill level every 100ms
    do {
        b = snd_pcm_avail(handle);
        c = a - b;
        printf("c:%ld\n", c);
        usleep(100000);
    } while(c > 4096);

    snd_pcm_drain(handle);
    snd_pcm_drop(handle);
    usleep(100000);
    snd_pcm_hw_free(handle);
    snd_pcm_close(handle);
    return 0;

exit:
    printf("Error occured!\n");
    return -1;
}