An MPEG transport packet stream or the like is modified to provide concatenated synchronization bytes at an output of an interleaver receiving the modified packet stream. A conventional sync byte located in a first transport packet is replaced with a first substitute sync byte. A conventional sync byte located in a conventional sync byte position of a second transport packet is deleted. Another byte from the second transport packet is moved to the position of the deleted sync byte to open a desired byte position in the second transport packet. A second substitute sync byte is inserted into the desired byte position. The first and second transport packets and the desired byte position are selected to provide the first and second substitute sync bytes at locations in the modified packet stream where the first substitute sync byte will be concatenated with the second substitute sync byte at the output of the interleaver. The transport packet stream can be further modified to provide concatenated auxiliary bytes at the output of the interleaver.