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I am trying to create a videofile and it gets to about 20% then stops. The file is M2TSfootage with jpegs so nothing unusual, approx 1 hr40mins. I have never had this problem before so any ideas would be grateful. Is making an iso file an alternative? If so how can I do this? Thanks.

Do you have any transitions, effects, etc. that would appear around the 20% mark? Could also be a corrupt clip at that point.