Today I encountered my first m2ts file, the file format typically found on blu-ray disks. The original format was an iso file so I mounted it and copied out the movie file, named "00074.m2ts." I was perplexed as to how to open it. I searched for ways to either convert it out of the format or for a mac application that could view the file. Some solutions talked about using mpeg streamclip to convert the file (didn't work), others talked about using dvd player on mac os x (didn't work since the initial file was an iso file). Another talked about using vlc (surprisingly, it didn't work either. I would get audio but there would be no video). I also tried their newer project, lunettes, tried quicktime x, quicktime 7 (with perian addon). They all didn't work.
As a last ditch effort I tried movist, a free, open source video viewer that I downloaded a while ago. And it worked! Application can be downloaded , the latest version is 0.6.8. For some reason it could open a file that no other app that I tried could open. Just some background information about movist it's an application based off of ffmpeg as well as quicktime so it supports a variety of different movie formats. The interface is pretty nice especially when compared to vlc, though in my opinion the full screen options are somewhat cluttered and for some reason when in full screen once I pressed escape twice and it quit the app. So if you have a m2ts file you need to view movist should do the trick.
Edit: Mplayer could also open the file and its user interface is pretty nice I must admit. Mplayer can be found here. Though for some reason in mplayer I couldn't move around in the movie while I could in movist.