From owner-freebsd-hackers Wed Sep 23 13:24:38 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id NAA07924 for freebsd-hackers-outgoing; Wed, 23 Sep 1998 13:24:38 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from labinfo.iet.unipi.it (labinfo.iet.unipi.it [131.114.9.5]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id NAA07778 for ; Wed, 23 Sep 1998 13:24:11 -0700 (PDT) (envelope-from luigi@labinfo.iet.unipi.it) Received: from localhost (luigi@localhost) by labinfo.iet.unipi.it (8.6.5/8.6.5) id UAA07940; Wed, 23 Sep 1998 20:33:47 +0200 From: Luigi Rizzo Message-Id: <199809231833.UAA07940@labinfo.iet.unipi.it> Subject: Re: backport of atapi-cd to -STABLE To: mike@smith.net.au (Mike Smith) Date: Wed, 23 Sep 1998 20:33:46 +0200 (MET DST) Cc: netmonger@genesis.ispace.com, oppermann@pipeline.ch, abial@nask.pl, hackers@FreeBSD.ORG In-Reply-To: <199809232014.NAA03628@dingo.cdrom.com> from "Mike Smith" at Sep 23, 98 01:14:40 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > Jitter correction is for the crappy (older) CD-ROMs.. Some sort of a thing > > about the lens jittering during use that can cause problems with generating ... > Jitter correction has to do with fixing up the raw audio data, it has > nothing to do with the digital side of things. "len jitter" wouldn't > affect the audio data - when a bit comes off the disk it's either a 1 > or a 0, and it either passes the DRS check or it's fixed if it's wrong. to clarify, the so-called jitter correction in "cdd" serves for those drives whose firmware does not guarantee that the data you get from the disk are for the block you requests and instead could give you data for a nearby block (presumably, but this is just an assumption, from time to time the firmware misses a block and passes you the next one). the way to do the correction is to read overlapped sections from the disk and compare the boundary block to make sure that they overlap as expected. On a drive that does not need jitter correction you lose a lot of speed. cheers luigi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message