Thanks. 1M didn't work (dd: bs: illegal numeric value), so I just put in 1000000 and got about a minute. Here's the new file. I guess I didn't notice the first test file I made was about the same size as the original, so it just transcoded it; didn't clip it. At any rate, this new file is only 50MB, not 650MB.
note: use lower case "m" for the bs argument on BSD (including OS X)
50MB clip
test1.mkv
Original file
original.mkv - Google Drive
Also, turns out the file doesn't not play well with HW acceleration off. For some reason it worked once, but I tried again, and it plays like crap on the ODroid with acceleration off.
So, any help getting this file, and others like it to play, is greatly appreciated. Or at least figuring out why it doesn't play so I can avoid them.