Editing Simultaneous substitution (section)

===Portions of programming lost===
Due to the high number of simultaneous substitutions requested by Canadian broadcasters, portions of programs are sometimes lost. This may occur for a variety of reasons, including the cable provider erroneously timing the substitution or substituting over the incorrect distant signal, the Canadian broadcaster making a scheduling error when requesting a substitution, the American broadcaster making a last minute change to its schedule, or adverse weather conditions sometimes affecting a Canadian station's local signal. In addition, should a Canadian network interrupt its programming to provide information on a [[breaking news]] event while simsubbing an American show, the American program cannot be telecast.

With the increasingly common practice of American networks extending programs by one to two minutes into the start of the next hour in order to avoid audience loss,<ref name="HouseExtend">{{cite web|title=Extended episode of ''House'' could plague DVR users|url=http://latimesblogs.latimes.com/showtracker/2008/11/house-runover-m.html|newspaper=[[Los Angeles Times]]|date=November 2008|access-date=September 13, 2009}}</ref> such errors are sometimes unavoidable if the Canadian station is not able to match the altered start time. This slight differentiation in timing between the Canadian and American stations can lead to a short period during which the Canadian viewer is watching the original American station's signal before the Canadian network starts its simsubbing, resulting in the show's jumping back to the start again. This is not a problem for American viewers who choose to watch the same network across time slots, but Canadian viewers could miss critical content. The timing is often rectified by tape delaying the overlaid content and forgoing a minute of ad time in the following commercial break to quickly catch back up with the American broadcast.