A comment on yesterday’s blog entry got me thinking and doing some research about how the aspect ratios work, and something finally clicked. I finally understand how it works. :)
The video aspect ratio isn’t just a simple calculation of height/width, it’s the ratio at how you want the playback displayed. Fullframe is 1.33:1, flat is 1.85:1 and scope is 2.35:1. It all makes sense, now. I didn’t need to scale my videos down to 640×480 to force the resolution to 1.33, I just needed to either tell mplayer to playback at a different aspect, or fix Matroska so the aspect ratio was correct. I ended up doing the second one.
Turns out it wasn’t (necessarily) a bug in mkvtoolnix, just me not passing in another option. Actually, I didn’t even know about it tell I looked at the man page some more. Turns out there’s an –aspect-ratio flag you can use when setting it for different video streams (have I mentioned that Matroska can hold multiple video and audio streams? To say nothing of attachments, chapters, DVD menus and subtitles … why are you still using AVI?). By not setting that flag (this is where I think the bug is) it defaulted it to 1.5, even though the AVI had it set at 1.33. Using the argument –aspect-ratio 0:4/3 fixed everything though. And I don’t have to rescale my video anymore, I’m glad about that one.