[pskmail] New snapshot adds file compression
- From: Rein Couperus PA0R <rein@xxxxxxxxxxxx>
- To: pskMail mailing list <pskmail@xxxxxxxxxxxxx>
- Date: Thu, 19 Oct 2006 15:30:31 +0200
There are new snapshots for client and server in the snapshot directory,
containing the changed files...
I have written 3 new perl modules:
cbh_code.pl
cbh_decode.pl
wordcount.pl
These can be used stand-alone if you want to experiment (-h helps).
They do context based huffman coding (based on a multilingual
(English/German/Dutch) word list of 14k), + gzip + base64 coding.
This is the best compression which can be achieved with plain text.
Some (larger) files compress 6x (leaving only 16% of the size), some
(like .jpg pics) do not compress at all, as they have a very high
entropy factor...
Words are coded with 2 (256 most used) or 3 bytes. Unknown words are
just inserted into the data stream without coding. The resulting message
is then gzipped and b64 coded for transport through pskmail.
At a later stage I will upgrade to b127 coding, which will be 12.5%
better, but for that we need a better interface to gMFSK.
I have changed the meaning of the Download button:
If you type the mail number into the text input field a the bottom it
compresses and downloads that mail in compressed form.
If you type a filename and click the download button. The system tries
to compress and download that file from the ~/pskdownload directory of
the server.
The Read button works the same way with noncompressed info.
I have added a progress indicator to the GUI.
The wiki pages (client installation -> add ~/mail/downloads dir, and
client operation) have been adapted to the new situation (the
installation procedures still have to be adapted).
73,
Rein PA0R
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