Apparently precompressor is a general term [1] that applies here:

> A precompressor is a computer program, which alters file content so that a real lossless compression program will achieve better results than without precompressing. This is possible by creating such patterns that compression programs will recognize.

In this case the altered content is (quoting the README) "decompressed data from the original file together with reconstruction data"). So confusingly enough its precompressing includes decompressing.

I don't think "precomp" is a real accurate name for the whole tool, but that might be where it came from.

With no flags it will precompress (including decompressing) and compress. With -cn, it will precompress alone. With -r, it will decompress and...I dunno, postcompress (including compressing)?

[1] https://findwords.info/term/precompressor

No it takes decompressed data and tries to recompress it better than it was by adding a pre-compressor to the compression process.

The terminology in the readme is strangely inverted. 'Compress' seems to mean decompress and vice versa. This extends to the source code itself. Perhaps a language barrier?

> Perhaps a language barrier?

The two words in German are Komprimieren (compress) vs Dekomprimieren (decompress). Not much potential to mix up here.

Yeah, the name was better for the initial versions of Precomp that basically only did the decompression part (like using "-cn" now) and prepared the data before further compressing it with other tools. It also has the downside of being a common term (abbrevation of precomposition) in image/video editing.

Also, for other stream types like JPG and MP3, even "-cn" directly compresses the data without being able to see the intermediate decompressed representation, so in these cases Precomp (re)compresses.

But well, it's just a name and I decided to stick with it, changing it several times would've lead to confusion, too.

Recomp