  Unity is a software specifically designed for the development of video games.
However, due to its programming possibilities and the polyvalence of its
architecture, it can prove to be a versatile tool for stimuli presentation in
research experiments. Nevertheless, it also has some limitations and conditions
that need to be taken into account to ensure optimal performance in particular
experimental situations. Such is the case if we want to use it in an
experimental design that includes the acquisition of biometric signals
synchronized with the broadcasting of video and audio in real time. In the
present paper, we analyse how Unity (version 5.5.1f1) reacts in one such
experimental design that requires the execution of audio-visual material. From
the analysis of an experimental procedure in which the video was executed
following the standard software specifications, we have detected the following
problems desynchronization between the emission of the video and the audio;
desynchronization between the temporary counter and the video; a delay in the
execution of the screenshot; and depending on the encoding of the video a bad
fluency in the video playback, which even though it maintains the total
playback time, it causes Unity to freeze frames and proceed to compensate with
little temporary jumps in the video. Finally, having detected all the problems,
a compensation and verification process is designed to be able to work with
audio-visual material in Unity (version 5.5.1f1) in an accurate way. We present
a protocol for checks and compensations that allows solving these problems to
ensure the execution of robust experiments in terms of reliability.
