Editor Thelma Schoonmaker has not seen an entire scene yet with the actors de-aged.
There seems to still be a lot of work to be done on the motion-capture side, as Schoonmaker still hasn't seen a single scene yet where the cast is de-aged. So though the plan is to have the first half of the movie all in flashback, that could change once she can finally show Scorsese what she gets out of the footage after editing it.
"I haven’t gotten a whole scene where they’re young," Schoonmaker told Yahoo, "And what I’m going to have to see, and what Marty’s going to have to see is, ‘How is it affecting the rest of the movie when you see them young?’"
A legendary Scorsese movie was used to test the de-aging motion capture for De Niro.
Business Insider spoke to De Niro in May 2017 and brought up "The Irishman," which he said he had already begun doing motion-capture tests for.
"I did a scene from 'Goodfellas' and they worked on that piece and we've been slowly moving along," he said. "We're going to make it great."
"The Irishman" could show De Niro as young as his late 20s.
"The Irishman" producer Gastón Pavlovich gave Cinemablend in 2017 a glimpse of how extensive Industrial Light & Magic may go with the de-aging.
"We were able to film Bob and just do a scene, and we saw it come down to when he was like 20, 40, 60, so we're looking forward to that," he said. "Imagine seeing what De Niro looked like in 'The Godfather 2' days, that's pretty much how you're going to see him again."
De Niro was in his late 20s when he played young Vito Corleone in the flashbacks scenes of "Godfather II."