Ripping wav files from iso image

[Benjamin Scott]

On Apr 25 at 1:13pm, Whelan, Paul wrote:
> Does anyone know how to rip tracks off an iso image?
> I thought I'd be clever and just dd one of my new cd's to my hard drive
> for later ripping/encoding of the tracks.

    Short answer:

    You can't do that.  The "image" you extracted with dd is useless and can be 
deleted. To extract audio, you need to use CD Paranoia on the disc directly.

    Long answer:

    "ISO image" is short for "ISO-9660 filesystem image".  ISO-9660 was the 
original industry standard for *data* CDs.  It defines things like file name 
format, directory structure, block structure, and layout on disc.  It has 
nothing to do with audio CDs.

    Standard audio CDs -- those used for regular consumer music -- are in a 
format called CDDA (Compact Disc Digital Audio).  CDDA is also called "Red 
Book audio".  CDDA contains nothing like an ISO-9660 filesystem structure. 
CDDA discs contain from 1 to 99 tracks.  Each track contains a stream of 
digital audio.  There's a TOC (Table Of Contents) which allows CDDA players to 
find the tracks, and some other magic metadata, too.

     While I've seen software which allowed you to extract a "raw image" of a 
CDDA disc, this isn't an ISO image.  I'm not even sure there's any kind of 
standard for storing a "raw image" of an audio CD.

    I *am* sure that one cannot use "dd" to extract the contents of a CDDA disc. 
The "dd" command, like most everything in *nix, assumes a file is a single 
stream of data, with no "forks" or other special "metadata".  CDDA discs do 
not fit into this paradigm.

    This is why cdparanoia (CDP) exists in the first place.  First and foremost, 
CDP reads CDDA from a disc and dumps it into files.  One doesn't use "dd" to 
rip an audio disc; one uses CDP.  CDP additionally performs a lot of tracks to 
detect and recover from read errors.  As noted above, CDDA is an audio 
*stream*.  It isn't block-based like a hard disk is.  So error detection and 
correction is a lot more complicated then one might expect.

    Using "dd" to extract an ISO-9660 filesystem image isn't really a good idea, 
either.  I'm a bit fuzzy on the details, but suffice it to say that it doesn't 
always work.  Using special-purpose tools such as "readcd" is a better idea.

    Hope this helps,

-- 
Ben <dragonhawk at iname.com>