Described is the adding of padding to a content file (e.g., image and/or audiovisual file) for anticipated subsequent use such that the content file need not be re-encoded to add metadata and other data to it. For example, padding may be added to an image file directly after an image file directory, whereby the directory can grow as needed into the padded space. Metadata can likewise be added to the padding, e.g., from the opposite direction that the directory extends into the padding. The padding may be added on the first re-encoding of the file, reducing or eliminating the need for subsequent re-encoding. The padding also may be used to track dead space in the file, with adjacent regions of dead space coalesced into a single region of dead space.