Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!umd5!ames!amdahl!pyramid!oliveb!intelca!mipos3!cpocd2!howard From: howard@cpocd2.UUCP (Howard A. Landman) Newsgroups: comp.ivideodisc Subject: Re: CD (roms) question Message-ID: <1060@cpocd2.UUCP> Date: 12 Jan 88 18:51:57 GMT References: <7813@eddie.MIT.EDU> Reply-To: howard@cpocd2.UUCP (Howard A. Landman) Organization: Intel Corp. ASIC Systems Organization, Chandler AZ Lines: 43 In article <7813@eddie.MIT.EDU> nathan@eddie.MIT.EDU (Nathan Glasser) writes: >What exactly is the capacity of a standard size CD, both in bytes and >in playing time for music (assuming a standard speed)? I've been >wondering this since I have this feeling that music CD's are quite >wasteful of space. Some of them may have only about a half an hour's >worth of music, whereas others have almost an hour. Some have 9 songs >and some have 25 songs. Is there a limit to the number of "tracks" >that they can have? If you are seriously interested in these questions, there have been a couple of excellent, detailed, and *long* postings in rec.audio recently. Try to read them if they haven't expired. I'll summarize briefly: First the easy part. A CD, by definition, may have no more than 99 tracks. This is so a 2-digit decimal display is guaranteed to be sufficient. Each track may be subdivided into no more than 99 indices (same reason). Very few music CDs actually contain indices, and many CD players don't support them. A few test disks with 99 tracks (and some tracks with 99 indices) can be had. The playing time question is more complicated than you might think. While there is a theoretical upper bound due to the size of the disk and the track density, in practice this can not be reached because of distortions caused by non-flatness in the plastic near the outer edge of the CD. When CDs were first released, the practical maximum was around 72 minutes. Since then, improvements in manufacturing techniques have increased this to around 75 or 76 minutes. The usable data is given approximately by: 2 bytes 44,100 samples 60 sec 2 channels x -------------- x -------------- x ------ x ~75 min channel-sample second min and if I haven't messed up my arithmetic, that comes out to about 757 MB. I seem to recall a number more like 550 MB fro a discussion about CD-ROM, so there may be some added redundancy or some other factor I haven't taken into account. -- Howard A. Landman {oliveb,hplabs}!intelca!mipos3!cpocd2!howard howard%cpocd2.intel.com@RELAY.CS.NET One hand clapping sounds a lot like two hands clapping, only quieter.