The 17-year-old who makes funny movies for deaf children

“Seeing my son being able to sit down and understand the film and see things he hasn’t seen before in eight years is amazing.”

For Toby, an eight-year-old who is deaf, watching movies or TV on streaming platforms can sometimes be a little pointless, because many of them don’t have sign language versions.

“We have captions, but they don’t really do anything for him because he goes pretty fast. He just watched and didn’t get much out of it,” his father Jarod Mills told Radio 1 Newsbeat.

But now, Toby has some help thanks to an app developed by a 17-year-old student.

Mariella Satow, who has dual UK-US citizenship, lives in the UK but has been stuck in New York since summer 2020 due to Covid travel restrictions.

In that new blocking phase, Mariella created a signature app called SignUp.

She came up with the idea while teaching American Sign Language (ASL) on her own, one of hundreds of sign languages ​​used around the world.

Mariella wanted to watch TV shows to help her learn, so she was disappointed to find that few had signed versions.

According to research from The Big Hack from the disability charity Scope, many streaming platforms offer subtitles and audio descriptions, but not sign language.

It took Mariella a year to develop the technology, with lots of help from ASL teachers and the deaf community.

The app is available in the US as a Google Chrome extension, with an interpreter appearing in a box once the movie starts playing.

At the moment it only works on Disney Plus movies, because that’s where Mariella thought she could help most of the kids.

“My sister and I were avid movie viewers when we were younger, and I couldn’t imagine it wasn’t part of our childhood,” he tells Newsbeat from New York.

Jarod, who works in Kentucky at a school for deaf children, says it was “exciting” to see Toby use Mariella’s invention.

“The app creates a level playing field,” he says.

“Children are getting that understanding and information like any hearing child does: they learn a language even before they go to school.”

Deaf people in the UK face many of the same barriers when it comes to film and TV.

“A hearing person can spontaneously go to the movies. While people who rely on subtitles have to make sure there is adequate viewing at a time when we are free,” says Cardiff-based 27-year-old Stacey Worboys.

“I wish I could go anytime without having to change my plans or book a break from work.”

Stacey says she has never encountered any signing service “that will allow you to add an interpreter to play the whole movie.”

He has learned British Sign Language (BSL) and is comfortable with subtitles when watching TV shows and movies.

But he feels that having an interpreter would make things “more inclusive”, especially for someone who might have a hard time with subtitles.

Stacey and Toby aren’t the only people welcoming Mariella’s app. It now has thousands of users and has been working hard to juggle its A-level studies.

The time difference from New York to his school in Rugby, Warwickshire means he sets his alarm for 5am.

She admits it’s “a bit difficult” – but the upside is that it gives her time to work on SignUp once the lessons are over.

The positive reaction from teachers and parents kept Mariella motivated to face early departures.

“The most significant comments are when it’s the first time a child has full access to a movie. The numbers don’t matter much, it’s the messages,” she says.

Stacey says a UK version of an app like SignUp would make movies and TV “more accessible” to the deaf community, especially since sign language is often the first language of deaf people.

Mariella is up for the challenge and hopes to make a British Sign Language version of her app for other streaming platforms like Netflix and Amazon Prime.

“There are more than 300 sign languages ​​used all over the world, so it’s going to take a long time to get all those versions,” he says.

Disney hits like Frozen, Moana and The Incredibles – Mariella’s favorite film – have all been signed to SignUp and Mariella has had requests to do hundreds of other films.

“I can’t believe how big it got,” he says.

“I had no idea what I was throwing into the universe.”

Follow Newsbeat on Instagram, Facebook, Twitter And Youtube.

Listen to Newsbeat inhabit at 12:45 pm and 5:45 pm on weekdays – or listen again here.