When I try to run mediafilesegmenter with the following mediafilesegmenter -iso-fragmented -z frame_index.m3u8 \ -f 720p -i index_720p \ -k key.bin -stream_encrypt -P -K <url> \ -B seg_720p -t 6 source.mp4 I get the following output ISO fragmented mode, forcing segments to start with I-Frame Processing file source.mp4 track 2 of source.mp4 contains more than one valid time mapping Unable to find any valid tracks to segment. Segmenting failed (-15650). What specifically should I be looking for in my MP4 that would be causing this?