1. A method comprising: receiving object detection metadata in a metadata track corresponding to video data; determining pixel dimensions of the video data; extracting metadata from the object detection metadata to obtain extracted metadata, the extracted metadata comprising dimensions of the video data in pixel-independent space; extracting a detected-object entry from the metadata track, the detected-object entry comprising information that provides a location of an object detection perimeter and dimensions of the perimeter; scaling, by a data processing system, the information that provides the location and the dimensions of the perimeter using the pixel dimensions of the video data and dimensions of the pixel-independent space, wherein the detected-object entry includes a detected-object index value corresponding to a particular object and wherein another detected-object entry corresponding to a different frame of the video data includes the same index value, indicating that the particular object occurs in both frames.