Speaking of silly mistakes, I was backing up some Cantonese DVDs for Clara and wondered why the resulting files were way larger than I expected.

$ ls -lh *mkv
==> 653M Forensic Heroes - s01e07.mkv
==> 692M Forensic Heroes - s01e08.mkv
==> 953M Forensic Heroes - s01e09.mkv
    
$ mkvinfo *s01e09*
==> [..]
==> | + Track
==> |  + Track number: 2 (track ID for mkvmerge & mkvextract: 1)
==> |  + Track UID: 2
==> |  + Lacing flag: 0
==> |  + Name: Stereo
==> |  + Language: chi
==> |  + Codec ID: A_AC3
==> |  + Track type: audio
==> |  + Audio track
==> |   + Channels: 2
==> |   + Sampling frequency: 48000.0

Whoops! I did AC3 passthrough, instead of transcoding. I must have been looking at my LaserDisc demodulator before I ran that.