ffmpeg -i s04e07.mkv -vf "idet" -f null - 2>&1 | grep "Single frame detection" Deinterlace only the problematic sections with yadif :

Now go — process your Season 4 files, and try not to think about the Vat of Acid episode’s aspect ratio errors.

Enter : the portal gun of video processing. Brutal, efficient, and occasionally destructive if you misplace a -map flag. 1. The Glitchy Source Problem Many S04 encodes come from web sources with VFR (variable frame rate) . This desyncs audio during the Snake Jazz scene. Fix it by forcing CFR (constant frame rate):

ffmpeg -i s04e07.mkv -vf "yadif=mode=1:parity=auto" -c:v libx264 -preset slow -crf 20 output_deint.mp4 The AC-3 5.1 tracks often have dialogue buried in the center channel while the Portal Gun SFX blow out your speakers. Downmix to stereo with dynamic compression: