基于Alsa lib进行音量调节以及静音操作

你的名字 2022-08-05 00:51 682阅读 0赞

#include <stdio.h>
    #include <stdlib.h>
    #include <sys/ioctl.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <alsa/asoundlib.h>
    #include <fcntl.h>
    #include <unistd.h>
    #include <errno.h>
    #include <string.h>
    #include <sys/soundcard.h>
    
    #include "volume_interface.h"
    
    #define DEBUG(x,y...)	//{printf("[ %s : %s : %d] ",__FILE__, __func__, __LINE__); printf(x,##y); printf("\n");}
    #define ERROR(x,y...)	{printf("[ %s : %s : %d] ",__FILE__, __func__, __LINE__); printf(x,##y); printf("\n");}
    
    static char *alsa_mix_dev = "default";
    static char *alsa_mix_headphone_ctrl = "Headphone";
    static char *alsa_mix_digital_ctrl = "Digital";
    
    static void volume_init(char *alsa_mix_ctrl, snd_mixer_t **alsa_mix_handle_p, snd_mixer_elem_t **alsa_mix_elem_p)
    {
    	int alsa_mix_index = 0;
    	snd_mixer_selem_id_t *alsa_mix_sid = NULL;
    
    	snd_mixer_selem_id_alloca(&alsa_mix_sid);
    	snd_mixer_selem_id_set_index(alsa_mix_sid, alsa_mix_index);
    	snd_mixer_selem_id_set_name(alsa_mix_sid, alsa_mix_ctrl);
    
    	if ((snd_mixer_open(alsa_mix_handle_p, 0)) < 0)
    		DEBUG ("Failed to open mixer");
    	if ((snd_mixer_attach(*alsa_mix_handle_p, alsa_mix_dev)) < 0)
    		DEBUG ("Failed to attach mixer");
    	if ((snd_mixer_selem_register(*alsa_mix_handle_p, NULL, NULL)) < 0)
    		DEBUG ("Failed to register mixer element");
    
    	if (snd_mixer_load(*alsa_mix_handle_p) < 0)
    		DEBUG ("Failed to load mixer element");
    	*alsa_mix_elem_p = snd_mixer_find_selem(*alsa_mix_handle_p, alsa_mix_sid);
    	if (!*alsa_mix_elem_p)
    		DEBUG ("Failed to find mixer element");
    	if (snd_mixer_selem_set_playback_volume_range (*alsa_mix_elem_p, 0, 100) < 0)
    		DEBUG("Failed to set playback volume range");
    }
    
    static void volume_uninit(snd_mixer_t *alsa_mix_handle)
    {
    	if(alsa_mix_handle){
    		snd_mixer_close(alsa_mix_handle);
    	}
    }
    
    int volume_get(void)
    {
    	long ll, lr, vol;
    	snd_mixer_t *alsa_mix_headphone_handle = NULL;
    	snd_mixer_elem_t *alsa_mix_headphone_elem = NULL;
    
    	//Headphone channel
    	volume_init(alsa_mix_headphone_ctrl, &alsa_mix_headphone_handle, &alsa_mix_headphone_elem);
    	//处理事件
    	snd_mixer_handle_events(alsa_mix_headphone_handle);
    	//左声道
    	snd_mixer_selem_get_playback_volume(alsa_mix_headphone_elem, SND_MIXER_SCHN_FRONT_LEFT, &ll);
    	//右声道
    	snd_mixer_selem_get_playback_volume(alsa_mix_headphone_elem, SND_MIXER_SCHN_FRONT_RIGHT, &lr);
    	volume_uninit(alsa_mix_headphone_handle);
    
    	/*
    	//Digital channel
    	snd_mixer_t *alsa_mix_digital_handle = NULL;
    	snd_mixer_elem_t *alsa_mix_digital_elem = NULL;
    	volume_init(alsa_mix_digital_ctrl, &alsa_mix_digital_handle, &alsa_mix_digital_elem);
    	//处理事件
    	snd_mixer_handle_events(alsa_mix_digital_handle);
    	//左声道
    	snd_mixer_selem_get_playback_volume(alsa_mix_digital_elem, SND_MIXER_SCHN_FRONT_LEFT, &ll);
    	//右声道
    	snd_mixer_selem_get_playback_volume(alsa_mix_digital_elem, SND_MIXER_SCHN_FRONT_RIGHT, &lr);
    	volume_uninit(alsa_mix_digital_handle);
    	*/
    
    	vol = (int)((ll + lr) >> 1);
    	//DEBUG("volume_get vol %d, ll %ld, lr %ld", vol, ll, lr);
    	return vol;
    }
    
    int volume_set(int vol, volume_domain domain)
    {
    	snd_mixer_t *alsa_mix_headphone_handle = NULL;
    	snd_mixer_t *alsa_mix_digital_handle = NULL;
    	snd_mixer_elem_t *alsa_mix_headphone_elem = NULL;
    	snd_mixer_elem_t *alsa_mix_digital_elem = NULL;
    
    	if(vol > 100)
    		vol = 100;
    	if(vol < 0)
    		vol = 0;
    
    	if(vol == 0){
    		volume_mute();
    	}else{
    		volume_unmute();
    	}
    
    	//Headphone channel
    	volume_init(alsa_mix_headphone_ctrl, &alsa_mix_headphone_handle, &alsa_mix_headphone_elem);
    	//左音量
    	snd_mixer_selem_set_playback_volume(alsa_mix_headphone_elem, SND_MIXER_SCHN_FRONT_LEFT, vol);
    	//右音量
    	snd_mixer_selem_set_playback_volume(alsa_mix_headphone_elem, SND_MIXER_SCHN_FRONT_RIGHT, vol);
    	volume_uninit(alsa_mix_headphone_handle);
    
    	//Digital channel
    	//Digital channel 修改量减半，防止音量太大失真
    	volume_init(alsa_mix_digital_ctrl, &alsa_mix_digital_handle, &alsa_mix_digital_elem);
    	//左音量
    	snd_mixer_selem_set_playback_volume(alsa_mix_digital_elem, SND_MIXER_SCHN_FRONT_LEFT, vol / 2);
    	//右音量
    	snd_mixer_selem_set_playback_volume(alsa_mix_digital_elem, SND_MIXER_SCHN_FRONT_RIGHT, vol / 2);
    	volume_uninit(alsa_mix_digital_handle);
    	return 0;
    }
    
    int set_volume_mute_value(int val)
    {
    	int err = 0;
    	char *card = alsa_mix_dev;
    	snd_ctl_t *handle = NULL;
    	snd_ctl_elem_value_t *ctl_elem_value;
    
    	if (handle == NULL && (err = snd_ctl_open(&handle, card, 0)) < 0) {
    		ERROR("Control %s open error: %s", card, snd_strerror(err));
    		return err;
    	}
    
    	if((err = snd_ctl_elem_value_malloc (&ctl_elem_value)) < 0){
    		ERROR("Control %s open error: %s", card, snd_strerror(err));
    		snd_ctl_close(handle);
    		handle = NULL;
    		return err;
    	}
    
    	snd_ctl_elem_value_set_numid (ctl_elem_value, 11);
    	snd_ctl_elem_value_set_interface (ctl_elem_value, SND_CTL_ELEM_IFACE_MIXER);
    	snd_ctl_elem_value_set_name (ctl_elem_value, "Digital Playback mute");
    	snd_ctl_elem_value_set_integer(ctl_elem_value, 0, val);
    
    	if ((err = snd_ctl_elem_write(handle, ctl_elem_value)) < 0) {
    		ERROR("Control %s element write error: %s", card, snd_strerror(err));
    	}
    
    	snd_ctl_close(handle);
    	handle = NULL;
    	snd_ctl_elem_value_free (ctl_elem_value);
    	return err;
    }
    
    int volume_mute()
    {
    	return set_volume_mute_value(1);
    }
    
    int volume_unmute()
    {
    	return set_volume_mute_value(0);
    }