Tar doesn’t natively have an index to immediately seek to files in the tar archive, though I know that it’s possible to extend it with an index somehow, because pixz will do a parallel LZMA compression that involves generating and using an index for tar archives.
EDIT: Oh, I think I see what you mean. You’re saying that you want to use tar to store the redundancy files, not generate redundancy data for the file as a whole? Like, a tar of PAR2 files? I don’t think that that’ll work, because you’ll want redundancy for tar’s metadata too.
EDIT2: So what you want is a single bytestream with forward error correction, not a set of files that provide it.
kagis
It looks like this guy has an implementation, and says that he’s using Reed-Solomon, but that it’s also just his weekend project, so…shrugs