Gregory, You might want to move your question over to the Flac-dev mailing list.
A FLAC stream allows for additional metadata, including custom data which decoders will skip. However, metadata must come before the audio data, and thus you cannot append it to the end. You also won't be able to interleave redundancy data with the main data, and it seems to me like interleaving the data somewhat near it's counterparts would make more sense.
The ultimate redundancy technique that I follow is to use flac to cut the size in half, and then burn two copies of each FLAC file to my CD- R or DVD-R backup. I'm primarily worried about scratches on the disc, so saving each file twice seems to reduce the likelihood of data loss. Not to mention the fact that CD/DVD already have data redundancy techniques at two different levels of coding. I don't really feel like there is much need for more than that.
Brian Willoughby Sound Consulting On Apr 1, 2007, at 20:01, Gregory Maxwell wrote: Is there an obvious safe way to add some extra data to a flac file that spec decoders will happily ignore? I'd like to explore creating a tool which will add N extra redundancy frames at the end which will allow perfect decoding with up to ~N frames lost in the files. This would allow users to sacrifice a tiny amount of compression for a substantial increase in file robustness. This would also create a new potential audience for Flac: people who don't care about file size but care substantially about file robustness. A typical flac bloated back to the original wav size could lose roughly half its blocks and still remain perfectly decodable. http://planete-bcast.inrialpes.fr/article.php3?id_article=7 has a nice high performance error correcting library which would work well for this sort of application. _______________________________________________ Flac mailing list Flac@xiph.org http://lists.xiph.org/mailman/listinfo/flac
