# Earthworm Modules:
Compress_UA and Decompress_UA Overview

(last revised 9 July, 2002)

The compress_UA and decompress_UA modules implement the gencompress algorithm which is used with permission from Boulder Real Time Technologies, Inc., copyright 1997.

Compress_UA inputs selected trace data messages (TYPE_TRACEBUF), compresses the samples via the BRTT algorithm, leaves the header intact, and outputs the resulting message as TYPE_TRACE_COMP_UA. Trace messages are selected via SCN names listed in the .d file. Wildcards are allowed. The compressed data output can be tagged with compress_UA's installation_id and module_id (normal Earthworm behavior), or with the installation_id and module_id of the original uncompressed message.

Decompress_UA is the matching decompressor. Its output is identical to the input to the compressor. As with compress_UA, decompress_UA's output can be tagged with its own installation_id and module_id, or with those of the original message. This option allows the logo of the original data source to be preserved thru the compress/decompress operation.

In order to run compress_UA and decompress_UA, you must add TYPE_TRACE_COMP_UA message to 'earthworm.d'.

Module Index | Compress_UA Commands | Decompress_UA Commands