Question

How to fragment an mp4 file using ffmpeg.I have followed this command "How to output fragmented mp4 with ffmpeg?" but it almost doubles the file size. Is there any other way ?

Answer 1

I think you get a higher file size because you reencode it with higher bitrates than the input file.

In the linked answer, you can modify the settings for -ab and -vb:

ffmpeg -i infile.ext -g 52 
-strict experimental -acodec aac -ab 64k -vcodec libx264 -vb 448k 
-f mp4 -movflags frag_keyframe+empty_moov 
output.mp4

(Hint: Do not user -re if not necessary)

If you don't have the bitrates from the input file, use ffprobe to get it for all streams:

ffprobe -i input.mp4

(look for Stream#0:0, Stream#0:1 and so on and if it is Audio or Video)

Not tested: You can also try to copy the streams:

ffmpeg -i input.mp4 -g 52 
-strict experimental -c copy 
-f mp4 -movflags frag_keyframe+empty_moov 
output.mp4

(only works with mp4 input?!)