Douwe Osinga's Blog: The unbearable lightness of Movies

Monday, October 4, 2004

I was watching a not quite so interesting movie the other day with my wife; my wife expressed her opinion on the movie by falling soundly asleep. There’s this thing about movies you know that are not good but you haven’t finished. I know the movie is not going to get better, but I feel that if the movie does get better, it will save the lost time. Of course on another level I know the time is lost already; that’s were technology comes to the rescue.


WinDVD has this interesting feature that allows you to speed up the movie in steps of 5%. And they have a nice DSP trick that makes the sound, well, sound normal, only faster. So it turns out you can watch a bad movie 40% faster than normal, a normal movie 25% faster and a really good movie still 10% or 15% faster than normal.


It is an interesting experiment in data-compression of movies. As always, the more information something contains, the hardest it is to compress. A completely blue photo compresses better than a detailed picture, better movies are more complex, so they compress less easy.


Compressed movies are strange; I downloaded something to watch on the train. Unfortunately, the download didn’t finish in time, but it did almost. 97% or so. This was with bittorrent. Bittorrent doesn’t download files sequentially, it downloads bits in random order. So the file I had was almost the complete file, with just 3% random bits missing. The funny thing is, it played pretty well. Sure it had some hick-ups and scrambled frames, but it made me think.


What if we had a special BitTorrent for movies. It would use a compression scheme that would play the movie, no matter how little data was actually available. Sort of like progressive gifs, but obviously much more complex. The nice thing about such a scheme would be that a download would never be incomplete and neither would it ever be finished. You could always keep your torrent open, collecting more random bits of the movie and improve the quality of your movie.


Obviously the original source of the movie would have to be of very high quality, but depending on the server architecture, that could actually be the full DVD; clients would start downloading from this source and get there own, very compressed (at least in the beginning) version of this movie; however and this is crucial, each client would get a slightly different version, so that if would take away the original, the clients could improve their quality by just communicating with each other.