  Visual Speech Recognition (VSR) is the task of predicting spoken words from
silent lip movements. VSR is regarded as a challenging task because of the
insufficient information on lip movements. In this paper, we propose an Audio
Knowledge empowered Visual Speech Recognition framework (AKVSR) to complement
the insufficient speech information of visual modality by using audio modality.
Different from the previous methods, the proposed AKVSR 1) utilizes rich audio
knowledge encoded by a large-scale pretrained audio model, 2) saves the
linguistic information of audio knowledge in compact audio memory by discarding
the non-linguistic information from the audio through quantization, and 3)
includes Audio Bridging Module which can find the best-matched audio features
from the compact audio memory, which makes our training possible without audio
inputs, once after the compact audio memory is composed. We validate the
effectiveness of the proposed method through extensive experiments, and achieve
new state-of-the-art performances on the widely-used LRS3 dataset.
