Did you figure this out? I'm getting the same error: $ mediafilesegmenter -iso-fragmented -t 2 ./sample_spatial.mov Feb 17 2024 10:04:00.249: ISO fragmented mode, forcing segments to start with I-Frame Feb 17 2024 10:04:00.249: Processing file /Users/jon/my_dir/sample_spatial.mov Feb 17 2024 10:04:00.259: Format description for track index 3 mismatch with another track with same media type Feb 17 2024 10:04:00.259: detected mismatch in track - don't use this file /Users/jon/my_dir/sample_spatial.mov Feb 17 2024 10:04:00.259: Unable to find any valid tracks to segment. Segmenting failed (-17185). I'm using the latest mediafilesegmenter (Version 1.22 (659.13b-240124)