From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751506AbWB1Aor (ORCPT ); Mon, 27 Feb 2006 19:44:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751862AbWB1Aor (ORCPT ); Mon, 27 Feb 2006 19:44:47 -0500 Received: from watts.utsl.gen.nz ([202.78.240.73]:4264 "EHLO mail.utsl.gen.nz") by vger.kernel.org with ESMTP id S1751506AbWB1Aoq (ORCPT ); Mon, 27 Feb 2006 19:44:46 -0500 Message-ID: <44039CEF.3060508@vilain.net> Date: Tue, 28 Feb 2006 13:44:31 +1300 From: Sam Vilain User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051013) X-Accept-Language: en-us, en MIME-Version: 1.0 To: "D. Hazelton" Cc: Peter Gordon , linux-kernel@vger.kernel.org Subject: Re: CD writing in future Linux (stirring up a hornets' nest) References: <200602271647.48600.dhazelton@enter.net> <7e90c9180602271430m35051882jcc3e5b1608fb6be9@mail.gmail.com> <200602271724.39562.dhazelton@enter.net> In-Reply-To: <200602271724.39562.dhazelton@enter.net> X-Enigmail-Version: 0.92.1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org D. Hazelton wrote: >>>This value is also reported by the drive. I don't know about DVD drives, >>>but for CD drives it is a multiplier. 1x == 256K/sec transfer off the >>>disc [...] >>For CDs, 1x is actually 150 KByte/sec. > Well, I've been known to be wrong before, and this number was more based on > the fact that I once measured a sustained transfer rate of 1M/sec on a 4x > CDROM Think about audio. Single speed = 75 frames of 2352 bytes per second, or 176kB/s. However with data tracks you only get 2k per frame/sector, so that works out to be 153kB/s. Due to the CLV nature of CD-ROMs you may find the drive is faster reading some parts of the disc than others. >>According to WikiPedia, the DVD speed rating is almost 9 times that of >>CD speeds. I.e., 1x DVD is about 1.32 MByte/sec. > This was based on DVDx16 == CDx48 - I'm guessing someone is doing some monkey > work if a DVD is 9x a CD and a 16x DVD can't hit that mystical 52x of my > favorite CDRW drive in pure CD read mode. You can do a similar calculation with DVDs. While I can't find a reference for the maximum DVD total bitrate of ~10Mbit/s, this at 1.25 MByte/s this roughly agrees with the 1.32 quoted. Sam.