text: examine our multi-masking strategy and find that sampling two masks for each clip (long-range and short-range) to 
  be more effective than sampling just a single mask for each clip. 
  
  In Figure 8c, we explore different average spatial and temporal masking ratio, i.e. the spatial/temporal ratio of 
  the area that is covered by a mask on average for a clip. Recall that each mask is constructed by sampling several 
  (possibly overlapping) blocks and taking their union. We change the average spatial or temporal masking ratio by 
  changing a block spatial or temporal size, as well as the overall number of blocks. We found that low spatial or 
  temporal coverage results in a trivial prediction task, which degrades downstream performance. Based on those 
  results, we sample masks that remove roughly 90% of the frame and extend along the entire temporal dimension of 
  the clip by default. 
  
  In Figure 8b , we explore different block size given an effective spatial masking ratio of 90% and temporal ratio of 
  100%. We keep the masking ratio approximately constant by changing the block size and the number of block at the 
  same time. We find that sampling several blocks to perform better than sampling a single large block. Figure 9 
  visually illustrates the effect of sampling several smaller blocks to construct a mask. 