Determination of the absolute energy scale of cosmic-ray measurements is one of the present goals of great importance for astroparticle physics. Recently, significant progress towards this direction has been achieved by the Auger Radio Engineering Array (AERA), a digital detector of air-shower radio emission within the Pierre Auger Observatory. AERA pioneered the use of well physically motivated values in the analysis of radio emission of air showers such as energy fluence, and in application of the axially asymmetrical radio-emission footprint models for sparse arrays. For the time being, AERA is approaching a new milestone --- validation of the absolute energy scale of cosmic-ray observations with radio measurements. This analysis consists of several steps on different levels. The proper signal processing is the foundation of all higher level steps for a correct estimation of the energy scale. In the talk I will present a comprehensive evaluation of the signal processing pipeline of AERA from the perspective of a consistent estimation of the energy fluence.