Can I watch 1080p torrents while downloading? Most large torrent files (8-20 gb) take quite a while to download. Is there software for Mac OS X that allows me to watch them while downloading?
We need a torrent client that can download the movie file parts in order, not randomly.
We need a player that supports playing incomplete files.
We need a connection that is faster than the movie’s bitrate (and a torrent with enough peers obviously).


The torrent client

Previously I used BitThief. It is developed by a technology institute in Zurich. It didn’t have a polished GUI and took a little bit too much CPU while downloading.

There's new client I found thanks to @diimdeep. It is called qbittorrent and it is awesome.



You can see that while downloading it downloads as a normal torrent client – the parts are downloaded randomly:



But there is an option:



After that we can see that the rest of the file is being downloaded sequentially (blue – downloaded, green – requested):



The connection speed

How can we tell if the speed is good enough? By the estimated time of arrival (ETA):



If the movie is 1.5 hours and the ETA is 17 minutes, then the speed is sufficient.

The player

The player is and always has been mplayer (I don't know why the domain is Hungarian)


low cpu usage
plays almost anything (although very rarely it crashes and burns)
lots of options (boosting volume, control of cache on streams, indexing...)
arrow keys navigation (I can't live without that)
playing incomplete files (and reindexing them, which allows navigation)


I use MplayerX - a nice OSX gui. Download and associate movie files with mplayer (avi, mkg):



The final step is to to play the file after the downloading started:



That’s it.



Happy watching.