The SCF format version 3.00 has been designed with file compression in mind. No new information is recorded when compared to the version 2.02 format, except the data is stored in a manner conducive to efficient compression.
Experimentation (1) has shown that 16 bit SCF version 3.00 files can achieve a
9:1 compression ratio and 8 bit SCF files a 14.5:1 compression ratio. These
figures are for SCF files without quality values compressed using the
bzip utility. gzip tends to give between 20 to 40% larger files
than bzip. Compressed SCF files containing accuracy values tend to be
around 10% larger than those without accuracy values.
Whilst compression is not a specific part of the SCF standard, the size of trace files and the compression ratios attainable suggests that it is wise to handle compressed files. The Staden Package utilities, such as gap4 and trev, automatically uncompress and compress SCF files as needed.
Note that at present, on the fly compression, as just described, is not implemented for the Windows version of the package.