I thought we where pushing the limits at the time by playback of digital audio off memory and later even streaming off a floppy drive.
This goes to show that not only could the audio have been done but video.
Now to be honest they are using a sound blaster card which didn't exist for another 6 years or so Aug 87.
The only things that's changed is optimization and algorithms, improvements in software development tools, completely open documentation and countless examples as well as easy access to video source materials.
I wasn't able to capture video till around 1984 it was a black and white threshold and looked dreadful and took several seconds to capture 1 image. A wasn't able to capture a proper grey scale till 1987 and it was a board that cost several thousand dollars. Color video capture wasn't until in 1990 on a Sun work station, all of this was exotic and super expensive at the time.
It wasn't till 1995 with the Matrox meteor at $500 that decent high quality video capture was possible. We were just reaching 90 to 120 Mhz Pentiums at that time.
Imagine what could be possible with today's hardware if only the software where optimized?