mkvsplit

#!/usr/bin/env zsh
if [[ $1 -eq 0 ]] || ! [[ -f $2 ]]; then
    echo "Usage: $0 limit_in_kb source_file"
    exit 1
fi

((size_limit=$1*1024))
echo mkvmerge --split timecodes:$(
    LANG=C mkvinfo -v -v $2 |
    awk -F'[ ,()]+' '
        !vtrack && /Track number:/ {t=$5}
        !vtrack && /Track type: video at/ {vtrack=t}
        $3!="SimpleBlock" || $4!="key" || $7!=vtrack {next}
        $16-split_pos > '$size_limit' {
            printf("%s%s", comma, prev_time);
            comma=",";
            # print (prev_pos-split_pos)/1024 > "/dev/stderr";
            split_pos=prev_pos-10240;  # 10kb for file header
        }
        {prev_time=$14; prev_pos=$16}'
    ) $2 -o "${2:t:r}-split.${2:e}"
du ${2:t:r}-split*.${2:e}