A camera or other imaging device or other system configures its JPEG engine to produce a JPEG image that is in compliance with the JPEG specification but specially constructed. The configuration is chosen such that the JPEG image information for pixels of an image is stored in 8- or 16-bit groups, unlike a typical JPEG image in which image information is stored in groups of varying numbers of bits. A final software step reads the JPEG image information and constructs an equivalent MPEG I-frame. The 8- and 16-bit grouping in the JPEG image facilitates efficient conversion from JPEG to MPEG.