The following link will get you a full list of Recoll helper apps:
- Text, HTML, mail folders, Openoffice, and Scribus files are processed internally. Lyx is used to index Lyx files. Many filters need sed and awk.
- Openoffice: supported natively, but needs the unzip command to be installed.
- PDF: pdftotext is part of the Xpdf package.
- Postscript: pstotext.
- Microsoft Word: antiword.
- Microsoft Excel and PowerPoint: catdoc.
- Wordperfect: libwpd.
- RTF: unrtf.
- dvi: dvips.
- djvu: DjVuLibre.
- MP3: Recoll will use the id3info program to extract tag information. Without id3info, only the filenames will be indexed.
- Image file tags support with exiftool. This is a Perl program, so you also need Perl on the system. This works with just about any possible image file and tag format (JPG, PNG, TIFF, GIF, etc.).
Recoll will generally install without the helper programs. However, for the document types to be indexed to be handled properly, you'll want to install the helper applications if your installer program doesn't install these dependencies automatically.