The conditioning embeddings reach the generator through cross-attention. In cross-attention, the spatial positions of the video latent act as queries, while the prompt token embeddings act as keys and values. Each position computes how strongly it matches each token and pulls in a weighted mixture. That is why different regions of the frame can attend to different words: the region containing the boat queries "boat" most strongly, while the region containing rain queries "rainy". The prompt is therefore a control signal applied at every generation step, not a key that retrieves a stored video.
How Text-to-Video AI Works Under the Hood
From Prompt to Conditioning Signal
How Conditioning Enters the Generator
4 / 4
So how does that sequence actually steer the video? It enters through cross-attention. Picture the spatial grid of the video as a set of queries, and the prompt tokens as keys and values.
0:00 / 0:00