This document details the process SABnzbd uses to verify the integrity of downloaded files using PAR2 and repair them if necessary. PAR2 (Parchive 2) is crucial for Usenet downloads as it allows reconstruction of missing or corrupted data using redundancy files.
SABnzbd employs a multi-stage process involving internal checks and an external PAR2 command-line utility.
Before verification can begin, SABnzbd needs to understand the structure of the downloaded set according to the PAR2 index file (usually setname.par2). The function parse_par2_file handles this.