Well, in the PGCs there are two interesting flags: -seamless joint -STC discontinuity The first one indicates that the cells are linked in a seamless way or not The second one indicates the main clock has to be reset, because a new mux sequence starts. The new STC sequence should start at zero, to be compliant, thought..., but using VobBlanker or dvdshrink to cut titles it may start in a non-zero value. What VobBlanker does is to put STC flag accordingly to the VOB files, as it must be. A seamless flag not correctly set can produce playback problems, but I do not know any issue with a wrong STC discontinuity flag. Usually a STC discontinuity implies a non seamless joint, and my intention was to modify both flags. ... But I'm not completely sure so I decided to modify only the STC flag. jsoto EDIT: too many typos...