  This brief literature review studies the problem of audiovisual speech
synthesis, which is the problem of generating an animated talking head given a
text as input. Due to the high complexity of this problem, we approach it as
the composition of two problems. Specifically, that of Text-to-Speech (TTS)
synthesis as well as the voice-driven talking head animation. For TTS, we
present models that are used to map text to intermediate acoustic
representations, e.g. mel-spectrograms, as well as models that generate voice
signals conditioned on these intermediate representations, i.e vocoders. For
the talking-head animation problem, we categorize approaches based on whether
they produce human faces or anthropomorphic figures. An attempt is also made to
discuss the importance of the choice of facial models in the second case.
Throughout the review, we briefly describe the most important work in
audiovisual speech synthesis, trying to highlight the advantages and
disadvantages of the various approaches.
