As you've seen, with 64 characters in the input, that 90*6-bits = 67.5 (mostly unacceptable) 8-bit chars as your best "simple transform' compression. A bare 2/3rds compression, even if all the 8-bit chars were acceptable in a filename which the aren't.

Your best hope is if your filenames can be split into various fields that can be represented by a number that is shorter than the fields text representation. For example: if one component of the name was one of 'North', 'NorthEast', 'East', 'SouthEast', 'South', 'SouthWest', 'West', 'NorthWest', that same field could be replaced by a digit 0-7, or maybe just 4-bits in conjunction with some other field with upto 3-bits.

Without seeing examples of the filenames, and the range of values the fields within represent, it's hard to be more helpful.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

Edit: g0n - reparented at authors request

In reply to Re^3: URL string compression? by BrowserUk
in thread URL string compression? by punch_card_don

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.