Each segment of the trailer is a different MP4. They are all hosted on the AWS CloudFront CDN. My guess is, like somebody stated, they pre-rendered many videos, and use a lambda at the edge to decode a GUID in the URL into a S3 path.
We're not far from emotive TTS + photo realistic rendering in a real time engine, potentially with neurally generated models to match real time events or camera input.
Matrix 5 will be this, but you'll be in the trailer, and it'll reference real world events. And that's just the start.
The future of audio and video is going to be crazy.
And you can try the alpha of "version 2" by visiting this, which has improvements in synthesis and vocoder quality, and also lets people contribute:
This is far from state of the art, but you can see at the other end of the spectrum that it's an easy toy that anybody can use.
I'm working on a photo -> 3D rigged model system and model style transfer. You can follow me on Twitch or Twitter to see that when it's ready.
https://vo.codes/tts/result/TR:s1rj02g34ppc7bhq1m8bf6p3thny6
A few areas for improvement in the clip you posted:
I need to add better duration estimation. It's unfortunately truncated.
A lot of the community-trained voices don't fully leverage phonetic annotation, so some of the words fall flat.
I think the synthesizer has too much noise in it (you can see this in the image). The person who trained it probably used noisy data.
Finally, the universal vocoder isn't handling James Earl Jones' deep voice very well. It should be fine tuned.