In an MPEG file, a sequence header is placed before one or more groups of pictures (GOPs) and contains encoding and displaying parameters. The sequence header can be repeated in order to allow random access, but all the data elements of the repeated sequence header, except those concerning quantisation matrices, must have the same values as in the first sequence header. The repeated sequence header must precede in the bitstream either an I Frame or a P Frame.

To allow for better access and editing, many people place a sequence header after every GOP. In final output, some place fewer sequence headers in (every 5 GOPs, etc.) to save bitrate or make the file smaller.

If you need to add sequence headers to a file you can use the tool MPEG SequenceMaker in the Tools Section.