Some embodiments provide a media-editing application. The application includes several image processing destinations for performing operations on video images. The application includes a scheduling engine for scheduling disk read, decode, and graphics processing operations to perform on images to prepare the images for the several destinations. The scheduling engine includes a first set of instructions for scheduling images based on a speed at which a particular one of the several destinations processes the images when none of the destinations require images in real-time. The scheduling engine includes a second set of instructions for scheduling images based on a real-time clock when at least one of the several destinations requires images in real-time.