chn_setvolume_matrix
ret = chn_setvolume_matrix(c, SND_VOL_C_MASTER, SND_CHN_T_FL, left);
ret |= chn_setvolume_matrix(c, SND_VOL_C_MASTER, SND_CHN_T_FR,
ret |= chn_setvolume_matrix(c, vc, i, left);
ret |= chn_setvolume_matrix(c, vc, i, right) << 8;
ret |= chn_setvolume_matrix(c, vc, i, center) << 16;
int chn_setvolume_matrix(struct pcm_channel *c, int vc, int vt, int val);
#define CHN_SETVOLUME(...) chn_setvolume_matrix(__VA_ARGS__)