Set ALSA master volume from C code

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花落未央
花落未央 2020-11-27 15:20

I\'ve been looking for a simple C code example to set the master volume of the ALSA mixer but could not find anything simple for this supposedly common operation.

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  • 2020-11-27 15:43

    The following works for me. The parameter volume is to be given in the range [0, 100]. Beware, there is no error handling!

    void SetAlsaMasterVolume(long volume)
    {
        long min, max;
        snd_mixer_t *handle;
        snd_mixer_selem_id_t *sid;
        const char *card = "default";
        const char *selem_name = "Master";
    
        snd_mixer_open(&handle, 0);
        snd_mixer_attach(handle, card);
        snd_mixer_selem_register(handle, NULL, NULL);
        snd_mixer_load(handle);
    
        snd_mixer_selem_id_alloca(&sid);
        snd_mixer_selem_id_set_index(sid, 0);
        snd_mixer_selem_id_set_name(sid, selem_name);
        snd_mixer_elem_t* elem = snd_mixer_find_selem(handle, sid);
    
        snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
        snd_mixer_selem_set_playback_volume_all(elem, volume * max / 100);
    
        snd_mixer_close(handle);
    }
    
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