MKVtools is an application that provides the tools needed to process .mkv and .ogm videos. When you open either of these two types of video container files in MKVtools, you will be presented with a list of video, audio and subtitle tracks contained in the file. Sometimes there will be enough information for you to determine what each track represents. If not, you can select a video and an audio track (and optionally a subtitle track) to preview the tracks in an mplayer window.
Features
Convert a variety of video file formats like mkv, avi, mp4 and ogm to either avi files or mp4 files.
Intuitively select desired video, audio and/or subtitle tracks to process, with the ability to verify the selections using video preview.
Use presets for one step encoding for playback on a variety of hardware
Burn selected subtitle track (i.e., hard subtitles) into the video, though this requires that the video track must be re-encoded.
Control the font, size and positioning of the embedded subtitles.
Split .mkv videos into sections of a specified file size or by start/end time.
Delete tracks from .mkv files.
Join, mux and change the pixel aspect ratio of .mp4 videos.
Extract the selected tracks as individual video, audio and/or subtitle files.
Add jobs to a queue either individually or in batches via drag and drop so you can process multiple files overnight (registered copies only)

System Requirements
MKVtools is now intel only. Sorry. It has been tested on a MacBook Pro and a Mac Pro running Leopard (Mac OSX 10.5.x) with no known issues.