I'm getting a better understanding of how f**ked up my source video is. It's the 1st disc of a 4 disc set. A 2:20 prologue was jammed onto the movie. Discs 2..4 are okay. In the span of 22 frames, 'side data - GOP timecode:' goes from 00:02:53:10 to 00:00:00:00 to 00:05:25:03. In that span and thereafter, GOPs are permanently misaligned relative to keyframes. Any suggestions for fixing them? Since GOPs are part of the PES extension, is there a way to simply delete them as a test? Thanks -- Mark.