SV_REG_ADC_INPUT
[SOUND_MIXER_RECLEV] = {SV_REG_ADC_INPUT, 1, 0, 0, SV_ADC_MAX, 0},
v = sv_indirect_get(sc, SV_REG_ADC_INPUT) & SV_INPUT_GAIN_MASK;
sv_indirect_set(sc, SV_REG_ADC_INPUT, v);