: By default, MKVToolNix creates index entries (Cues) for every I-frame in video and subtitle tracks.
This forces cue points for every track (track 0 = all tracks). mkv index
Not all video converters are created equal. Poorly written transcoding software might fail to write the timecodes correctly. This results in a "timecode discontinuity," where the timestamps in the index do not match the actual frames in the video stream. The player gets confused trying to reconcile the map with the territory. : By default, MKVToolNix creates index entries (Cues)
Plex will attempt to generate a temporary index for MKV files on-the-fly, but this is CPU-intensive and slow. Pre-index your files using the FFmpeg method above. Poorly written transcoding software might fail to write
Ensures that if a file has multiple audio languages or subtitle tracks, they remain perfectly synced even after skipping around the video. Challenges with Missing or Damaged Indexes