Subject: Re: On-the-fly compression

From: [email-masked] (Nico de Vries [AIP-NL])
Date: Sun, 09 Oct 94 23:59:33 GMT

[email-masked] writes in article <[email-masked]>:
>
> Hello, I would like to know if anyone knows of existing source code to
> perform on-line data-compression; not the usual have-a-file-and-compress-it
> but something that would read continuously the serial input and produce
> compressed output. If we are using the "dictionary" methods then we can have
> a sample of similar data as the one we are going to compress on-line,
> build a dictionary and then use this dictionary for the real on-line
> application. May not be optimal, but won't be far from it.

A LZ engine combined with dynamic Huffman or arithmetic coding
reasonably fits your description and has compression close to that of
the LZ with static Huffman which is common nowadays. The maximum match
length of the LZ engine woudl determine the amount of characters the
output of the decompressor could be behind the input stream of the
compressor.

If the decompressor should not lag behing the input of the compressor
at all, dynamic Huffman compression, arithmetic compression or higher
order arithmetic compression can be used.

In case higher order arithmetic compression is used, the compression
will be beter than that of LZ + static Huffman, but much slower.

> Thanks.
> George Uphall

Take care,

     Nico de Vries.
--
[email-masked]  [AIP-NL, UltraCompressor II development]