2011年12月20日 星期二

主音量控制

【轉貼】Fred's blog

#include <stdio.h>
#include <alsa/asoundlib.h>  <--- libasound2-dev
int main(void) { int unmute, chn; int al, ar; snd_mixer_t *mixer; snd_mixer_elem_t *master_element; snd_mixer_open(&mixer, 0); snd_mixer_attach(mixer, "default"); snd_mixer_selem_register(mixer, NULL, NULL); snd_mixer_load(mixer); /* 取得第一個 element,也就是 Master */ master_element = snd_mixer_first_elem(mixer); /* 設定音量的範圍 0 ~ 100 */ snd_mixer_selem_set_playback_volume_range(master_element, 0, 100); /* 取得 Master 是否靜音 */ snd_mixer_selem_get_playback_switch(master_element, 0, &unmute); if (unmute) printf("Master is Unmute.\n"); else printf("Master is Mute.\n"); /* 取得左右聲道的音量 */ snd_mixer_selem_get_playback_volume(master_element, SND_MIXER_SCHN_FRONT_LEFT, &al); snd_mixer_selem_get_playback_volume(master_element, SND_MIXER_SCHN_FRONT_RIGHT, &ar); /* 兩聲道相加除以二求平均音量 */ printf("Master volume is %d\n", (al + ar) >> 1); /* 設定 Master 音量 */ snd_mixer_selem_set_playback_volume(master_element, SND_MIXER_SCHN_FRONT_LEFT, 99); snd_mixer_selem_set_playback_volume(master_element, SND_MIXER_SCHN_FRONT_RIGHT, 99); /* 將 Master 切換為靜音 */ for (chn=0;chn<=SND_MIXER_SCHN_LAST;chn++) { snd_mixer_selem_set_playback_switch(master_element, chn, 0); } /* 將 Master 切換為非靜音 */ for (chn=0;chn<=SND_MIXER_SCHN_LAST;chn++) { snd_mixer_selem_set_playback_switch(master_element, chn, 1); } return 0; }

compiler :

gcc  t1.c  -o  t1  -lasound


ref :
1. Fred's blog
2. Andes Core

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