On Sun, 2005-03-06 at 17:17 -0500, David & Renee MacDonald wrote: > I have backed up all my MP3 recordings onto an external hard drive. Does the > quality of the MP3s suffer from repeated copying like some image files > do(Jpeg)? > > David
Yes and no; MP3 and JPEG are both "lossy" compression schemes, which means that the process of creating such a file throws away part of the information in the original audio signal / image, generally because the information is deemed to have minimal significance. Both schemes typically have a tunable threshold, where the user may set the level of detail which is deemed to be significant. In practice, that significance level sets the balance between saving disk space and the quality of the resulting file. Once the file is created, though, it's the same as any other file, and you may make as many backups of it as you like without affecting the quality any further. Backups are bit-for-bit identical to the original files (well, they're supposed to be, anyway; if they're not, you've got BIG problems). I think the advice you got pertains to editing files; typically, you cannot edit a compressed file directly. You must first open it to the uncompressed form, make the modifications, then re-save it. At this point, the file has already lost some of the fine details due to the original compression, and the process of saving it after making modifications means that yet more detail will be lost. For this reason, you generally don't want to modify JPEG or MP3 files after they've been created unless you can't help it. _______________________________________________ Discuss mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/discuss
