Sparse in Space and Time: Audio-visual Synchronisation with Trainable Selectors
It addresses synchronisation for videos 'in the wild' where cues are infrequent and spatially small, which is an incremental improvement over dense cases like talking heads.
The paper tackles audio-visual synchronisation in general videos where cues are sparse in space and time, proposing a multi-modal transformer with trainable selectors to handle long sequences and showing effectiveness on both dense and sparse datasets with quantitative and qualitative results.
The objective of this paper is audio-visual synchronisation of general videos 'in the wild'. For such videos, the events that may be harnessed for synchronisation cues may be spatially small and may occur only infrequently during a many seconds-long video clip, i.e. the synchronisation signal is 'sparse in space and time'. This contrasts with the case of synchronising videos of talking heads, where audio-visual correspondence is dense in both time and space. We make four contributions: (i) in order to handle longer temporal sequences required for sparse synchronisation signals, we design a multi-modal transformer model that employs 'selectors' to distil the long audio and visual streams into small sequences that are then used to predict the temporal offset between streams. (ii) We identify artefacts that can arise from the compression codecs used for audio and video and can be used by audio-visual models in training to artificially solve the synchronisation task. (iii) We curate a dataset with only sparse in time and space synchronisation signals; and (iv) the effectiveness of the proposed model is shown on both dense and sparse datasets quantitatively and qualitatively. Project page: v-iashin.github.io/SparseSync