Carcassonne to Barcelona by Train

It depends on which route you take. Basically you have two options. The high speed coastal route which is not very scenic, you cross the mountains in a tunnel. Or the mountain route via Latour-de-Carol which is slower but very scenic.

There is only one possible route from Carcassonne to Barcelona by train, which more or less runs along the Mediterranean coast.

The train don't go through the Pyrenees in the mountains (if this is the type of landscape you are thinking of) but along the coast.
Going through the mountains would require several connections and would take 3 to 4 times longer.

For train questions, always ask the Man in Seat 61:

https://www.seat61.com/international-trains/trains-from-Barcelona.htm#Barcelona-other-france

Thanks a lot to all. I’ll study the train routes and schedules.
What about by bus? It’s the views I’m after!!

The high-speed train goes along the coast is somewhat interesting but at the high speed, it's hard to take in.

There is another route using local trains that goes through the coastal mountains. I took it twenty years ago: Carcassonne to Narbonne, Narbonne to Port Bou, and Port Bou to Barcelona. You can also do Port Bou to Gerona and Gerona to Barcelona.

From Port Bou to Barcelona, it's more or less a commuter train.

Many thanks again to all for very useful info.