[FFmpeg-user] Concatenating grows file size

[Cecil Westerhof]

I use the following Bash code to concatenate some video files:
    first=15
    last=20
    files=$(
        for i in $(seq ${first} ${last}) ; do
            printf "file ${PWD}/%05d.MTS\n" $i
        done
    )
    newFile=$(printf "%05d-%05d" ${first} ${last})
    ffmpeg -f concat -safe 0 -i <(echo "${files}") -c copy ${newFile}.mts

I would expect the resulting file to have the same size as the
original files, but the size grows. The input files are together
10.6 GB while the concatenated file is 10.9 GB. That is 3% extra. Is
this normal, or am I doing something wrong?

I am using version 4.1.4-1~deb10u1.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof