Command line conversion / joining utilities

[jxfish2]

Are there any command line based conversion utilities that will allow commands similar to the following:

Base_Program -sourcetype MKV -sourcefile My_Video.mkv -outputtype AVI -outputfile My_Video.avi -targetsize 1200MiB

Something that will automatically retain the same aspect ratio, while automatically shrinking the resolution to the desired final file size.

Of course the base_program should be able to handle multiple input source types, to include ISO, or the uncompressed ISO VOB files, MKV, MP3, etc.

Thanks in advance, and have a great weekend.

[jxfish2]

Ahhh, one more requirement.

It should be able to join multipart video files into a single final video file, using a similar command to the one above!