CODEWITHSUNDEEP
linuxalsalibalsalibasound
Brain
Brain

Reputation: 321

How to get PCM device path in ALSA?

What is the easiest way in ALSA library to get the file name of the physical playback device from a pcm handle or name?

For example for the pcm device hw:0,0 I would like to get the /dev/snd/pcmC0D0p. This is rather simple (just transfer the indexes), but for "default" or any other alias it is not so obvious.

Upvotes: 3

Views: 4126

Answers (1)

Brain
Brain

Reputation: 321

To answer myself. There is an indirect way to do this by obtaining the card and device number from the snd_pcm_info.

    int err;
    const char *device_name = "default";
    snd_pcm_t *pcm;

    err = snd_pcm_open(&pcm, device_name, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
    if (err < 0) {
        fprintf(stderr, "Failed to open audio device '%s': %s\n", device_name, snd_strerror(err));
        return false;
    }

    snd_pcm_info_t *info;
    err = snd_pcm_info_malloc(&info);
    if (err < 0) {
        fprintf(stderr, "Failed to allocate PCM info: %s\n", snd_strerror(err));
        goto fail;
    }
    err = snd_pcm_info(pcm, info);
    if (err < 0) {
        fprintf(stderr, "Failed to get PCM device info: %s\n", snd_strerror(err));
        snd_pcm_info_free(info);
        goto fail;
    }

    int card_no = snd_pcm_info_get_card(info);
    if (card_no < 0) {
        fprintf(stderr, "Failed to get PCM card number: %s\n", snd_strerror(card_no));
        snd_pcm_info_free(info);
        goto fail;
    }

    unsigned dev_no = snd_pcm_info_get_device(info);

    printf("The ALSA path is: /dev/snd/pcmC%dD%up\n", card_no, dev_no);
    snd_pcm_info_free(info);
fail:
    snd_pcm_close(pcm);

Upvotes: 2

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