Re: audio CDs and cdrdao vs. cdparanoia
On 7/5/2010 3:43 PM, Urs Thuermann wrote: Now my question is where these [CD-rip] differences come from and which results are the correct (better) ones. Audio CDs live in a world where there is no guarantee that any two passes across a sector will ever give the same result. For one thing, there is no error correction. Give up the idea of getting a correct, or perfect, rip; it's theoretically impossible. In fact, that's why cdparanoia exists. In the days of CD-ROM drives, the drives were not very good at ripping audio discs, and cdparanoia compensated for the problems. It was also unbelievably slow. Today, DVD drives have a much better disc transport, etc., and a lot of software is smarter than it used to be, so ripping is only a real problem with copy-protected CDs, and very damaged discs. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4c32dae1.70...@allums.com
Re: audio CDs and cdrdao vs. cdparanoia
On 7/5/2010 3:43 PM, Urs Thuermann wrote: Now my question is where these [CD-rip] differences come from and which results are the correct (better) ones. Here is a nice web site about CDs. It is about CD-Rs, but it has a lot of general info that anyone can benefit from, including about audio CDs. It is a good starting point. http://www.cdrfaq.org/ -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4c32dea6.5020...@allums.com
Re: audio CDs and cdrdao vs. cdparanoia
On 7/5/2010 3:43 PM, Urs Thuermann wrote: Now my question is where these [CD-rip] differences come from and which results are the correct (better) ones. Audio CDs live in a world where there is no guarantee that any two passes across a sector will ever give the same result. For one thing, there is no error correction. Give up the idea of getting a correct, or perfect, rip; it's theoretically impossible. Oh, I forgot. One more thing (and sorry to keep flooding the list replying to myself): There is an analog output and a digital output, and they are not equal. Your CD-drive or DVD-drive will treat them differently, and that conceivably may make a difference for you. I'm sorry, I cannot offer advice about what, if anything, to do with the analog output, but since you are probably only interested in the digital output, anyway, it's just as well. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4c32e05b.5080...@allums.com
Re: audio CDs and cdrdao vs. cdparanoia
On Mon, Jul 05, 2010 at 10:43:44PM +0200, Urs Thuermann wrote: For each CD I run cdrdao read-cd --datafile data.cdr --device /dev/sg0 toc and cdparanoia -d /dev/sg0 -B where /dev/sg0 refers to an Plextor Ultraplex 40max SCSI CDROM drive. [...] I can run cdrdao and cdparanoia repeatedly, say 10 times, and I get deterministic results, i.e. all runs of cdrdao give the same result and all runs of cdparanoia give the same result but the results of cdrdao and cdparanoia differ. Now my question is where these differences come from and which results are the correct (better) ones. With a suitable CDROM drive such as yours and CDs in reasonably good condition, there should be no need for cdparanoia's data correction feature. In fact, I found that it can sometimes do more harm than good, so I recommend disabling it (-Z), if only for testing purposes. You could compare your results to Exact Audio Copy (Windows, free for non-commercial use), which reportedly also runs on WINE. Another option would bei morituri, a CD ripper for Linux modelled after Exact Audio Copy. Regards, Mirko -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100706110434.ga20...@titus.informatik.tu-chemnitz.de
Re: audio CDs and cdrdao vs. cdparanoia
On Tue, Jul 6, 2010 at 4:04 AM, Mirko Parthey mirko.part...@informatik.tu-chemnitz.de wrote: [...] You could compare your results to Exact Audio Copy (Windows, free for non-commercial use), which reportedly also runs on WINE. +1. Also if you use EAC with AccurateRip enabled you can have quite good confidence in your results. Mark
Re: audio CDs and cdrdao vs. cdparanoia
First, I would like to second the suggestion of trying Exact Audio Copy (if a Windows environment is available) and comparing those results. +1 Second, I apologize for beating a dead horse, but in the event that a few people read my earlier posts, I wanted to make a correction to what I originally wrote. In particular, the statement that there is no error correction on audio CDs is wrong. The following (taken from ttp://www.cdrfaq.org/faq02.html) is rather long, but interesting: Subject: [2-15] What are jitter and jitter correction? (1998/04/06) (below) Subject: [2-17] Why don't audio CDs use error correction? (2007/08/08) (below) On 7/6/2010 2:27 AM, Mark Allums wrote: On 7/5/2010 3:43 PM, Urs Thuermann wrote: Now my question is where these [CD-rip] differences come from and which results are the correct (better) ones. Audio CDs live in a world where there is no guarantee that any two passes across a sector will ever give the same result. For one thing, there is no error correction. Give up the idea of getting a correct, or perfect, rip; it's theoretically impossible. In fact, that's why cdparanoia exists. In the days of CD-ROM drives, the drives were not very good at ripping audio discs, and cdparanoia compensated for the problems. It was also unbelievably slow. Today, DVD drives have a much better disc transport, etc., and a lot of software is smarter than it used to be, so ripping is only a real problem with copy-protected CDs, and very damaged discs. Subject: [2-15] What are jitter and jitter correction? (1998/04/06) The first thing to know is that there are two kinds of jitter that relate to audio CDs. The usual meaning of jitter refers to a time-base error when digital samples are converted back to an analog signal; see the jitter article on http://www.digido.com/ for an explanation. The other form of jitter is used in the context of digital audio extraction from CDs. This kind of jitter causes extracted audio samples to be doubled-up or skipped entirely. (Some people will correctly point out that the latter usage is an abuse of the term jitter, but we seem to be stuck with it.) Jitter correction, in both senses of the word, is the process of compensating for jitter and restoring the audio to its intended form. This section is concerned with the (incorrect use of) jitter in the context of digital audio extraction. The problem occurs because the Philips CD specification doesn't require block-accurate addressing. While the audio data is being fed into a buffer (a FIFO whose high- and low-water marks control the spindle speed), the address information for audio blocks is pulled out of the subcode channel and fed into a different part of the controller. Because the data and address information are disconnected, the CD player is unable to identify the exact start of each block. The inaccuracy is small, but if the system doing the extraction has to stop, write data to disk, and then go back to where it left off, it won't be able to seek to the exact same position. As a result, the extraction process will restart a few samples early or late, resulting in doubled or omitted samples. These glitches often sound like tiny repeating clicks during playback. On a CD-ROM, the blocks have a 12-byte sync pattern in the header, as well as a copy of the block's address. It's possible to identify the start of a block and get the block's address by watching the data FIFO alone. This is why it's so much easier to pull single blocks off of a CD-ROM. With most CD-ROM drives that support digital audio extraction, you can get jitter-free audio by using a program that extracts the entire track all at once. The problem with this method is that if the hard drive being written to can't keep up, some of the samples will be dropped. (This is similar to a CD-R buffer underrun, but since the output buffer used during DAE is much smaller than a CD-R's input buffer, the problem is magnified.) Most newer drives (as well as nearly every model Plextor ever made) are based on an architecture that enables them to accurately detect the start of a block. An approach that has produced good results is to do jitter correction in software. This involves performing overlapping reads, and then sliding the data around to find overlaps at the edges. Most DAE programs will perform jitter correction. Subject: [2-17] Why don't audio CDs use error correction? (2007/08/08) Actually, they do. It is true that audio CDs use all 2352 bytes per block for sound samples, while CD-ROMs use only 2048 bytes per block, with most of the rest going to ECC (Error Correcting Code) data. The error correction that keeps your CDs sounding the way they're supposed to, even when scratched or dirty, is applied at a lower level. So while there isn't as much protection on an audio CD as there is on a CD-ROM, there's still enough to provide perfect or near-perfect sound quality under
audio CDs and cdrdao vs. cdparanoia
When I rip audio CDs, I typically use both cdrdao and cdparanoia and compare the results to make sure that I really really have the correct digital audio data. I run Debian testing with current versions of cdrdao 1.2.2 and cdparanoia III release 10.2. For each CD I run cdrdao read-cd --datafile data.cdr --device /dev/sg0 toc and cdparanoia -d /dev/sg0 -B where /dev/sg0 refers to an Plextor Ultraplex 40max SCSI CDROM drive. Then I use my own small program to split the data.cdr file into wav files n.wav according to the toc file. I then compare these wav files with the trackn.cdda.wav files from cdparanoia. Alternatively, one could run sox trackn.cdda.wav cdda.cdr and then compare data.cdr to cdda.cdr. I most cases the results of cdrdao and cdparanoia are the same but for roughly 1 of 4 CDs one or more tracks differ. Sometimes this is the case for CDs with scratches but sometimes also for CDs with no obvious scratches where both, cdrdao and cdparanoia don't give any error message and do not seem to have any problems ripping the CD. I can run cdrdao and cdparanoia repeatedly, say 10 times, and I get deterministic results, i.e. all runs of cdrdao give the same result and all runs of cdparanoia give the same result but the results of cdrdao and cdparanoia differ. Now my question is where these differences come from and which results are the correct (better) ones. From the output to stdout I see that cdrdao uses the Paranoia DAE library and Joerg Schilling's SCSI library to actually read the audio CDs. With ldd I see it is not linked dynamically to these libraries. So one question is, do cdrdao and cdparanoia use different library versions? Regards, urs -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/ygfy6dpslq7@janus.isnogud.escape.de
Re: audio CDs and cdrdao vs. cdparanoia
On Lu, 05 iul 10, 22:43:44, Urs Thuermann wrote: Now my question is where these differences come from and which results are the correct (better) ones. From the output to stdout I see that cdrdao uses the Paranoia DAE library and Joerg Schilling's SCSI library to actually read the audio CDs. With ldd I see it is not linked dynamically to these libraries. So one question is, do cdrdao and cdparanoia use different library versions? Maybe it's just me, but after reading the cdparanoia FAQ[1] I wouldn't use anything else for CD ripping ;) [1] http://xiph.org/paranoia/faq.html I doubt (but have no proof) cdrdao can handle all errors that cdparanoia can handle. Regards, Andrei -- Offtopic discussions among Debian users and developers: http://lists.alioth.debian.org/mailman/listinfo/d-community-offtopic signature.asc Description: Digital signature
