Now here is something I did not know about. The Rio Car review at MPeX.net states the following (translated from German by AltaVista's Babelfish):

"By coincidence we are encountered the possibility of playing also files in tar the format. Tar is a Komprimierungstool originating from the Unix area. Complete albums can be stored and played so compressed in one tar file on the RioCar. There the RioCar from a Linux system exists is obvious this support. Only restriction: Within " types of GET " of an album cannot be selected TRACKS, since the Tar file is treated as an individual TRACK."

I never knew this. You can tar-up an album and it'll play as if it were one track? Interesting. Do the song titles change at each track boundary or what? This is interesting.

Perhaps maybe it's simpler than I'm making it out to be. Maybe a TAR file is just all the files appended together with a bit of header data (which emplode would ignore), thus being the same as if I'd just done a copy /b track1.mp3 + track2.mp3 combined.mp3, in which case there's nothing special about the empeg, it's just a coincidence of the file format.

You have to love Babelfish. This line from the translation struck me as funny:

"The display strikes almost all other Car audio Player around lengths."

I think what the original author was saying is "The display beats other car audio players by a long shot."

Yep, a tar file is nothing more than a header, followed by the files, each prepended by a small header. Since the headers are not valid MP3 frames, the decoder will skip them.

Tar is a Komprimierungstool...

Yep, a tar file is nothing more than a header, followed by the files, each prepended by a small header. Since the headers are not valid MP3 frames, the decoder will skip them.

Also, tar (Tape ARchive) isn't really a compression tool - any compression done must either be applied to the individual files prior to tar'ing them together or to the entire tar file after adding the individual files. Some implementations (most common, GNU tar) of the tar program allows compression as a command line option though - but it's not an inherent part of the tar file format. I doubt that the empeg would be able to play a compressed tar (not that compression would be very useful on mp3 files anyway).

Could be a useful trick if you ever run short on inodes...

/Michael

any compression done must either be applied to the individual files prior to tar'ing them together or to the entire tar file after adding the individual files

...or more usually by the tape drive hardware, specified by the device used to do the TAR activity.

Compression options as part of the command operate on the individual files added to the AR, and it shells out to a compression tool specified by a UNIX shell variable. I have only seen this on HP-UX, YMMV. I would not have thought that compressing the archive itself would be any use whatsoever since no other TAR utility (except the same flavour) would be able to do anything with it.

He was referring to an option to GNU's tar. It just automatically compresses the entire archive using gzip or bzip2 after the archive has been generated. Saves a little intermediate disk space because it doesn't have to write an intermediate file. The usage ``tar zcf archive.tar.gz [files]'' is roughly equivalent to ``tar cf - [files] | gzip -c > archive.tar.gz''.

By the way, most compression algorithms work much better on a large set of data than a small set, which is one reason why the compression is performed on the entire archive instead of the contained files.

Also, few people actually use tar to write to tape any more. There are usually more uselful utilites with more features and fewer bugs elsewhere. Your filesystem's dump utility and cpio come immediately to mind.