If you have a collection of m4s files and an init.mp4 , you can always reconstruct a full MP4 by simple concatenation. If the init is missing, you'll need to extract codec parameters from one of the fragments or the MPD manifest.
# Option 1: Find init (often "init.mp4" or "video_init.m4s") # Option 2: Use FFmpeg to generate a dummy init from first segment (imperfect but works) ffmpeg -i seg0.m4s -c copy -f mp4 dummy_init.mp4 cat dummy_init.mp4 seg*.m4s > output.mp4 Better: Use or Bento4 to reassemble correctly:
1. What is an m4s file? An m4s file (Media Segment for MPEG-DASH) is a chunk of video or audio data used in MPEG-DASH (Dynamic Adaptive Streaming over HTTP) streaming. The "m4" stands for MP4 -based container, and "s" stands for segment .