This document is written by one of our users:
K.G.H. Nicholes of Concise
Logic
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Introduction
VerifyCD's Purpose VerifyCD Versions Operating VerifyCD Tweaking VerifyCD for your project Sonoconsult's description of VerifyCD's use in creating an Audio Master Installation/licensing Acquiring and using your License Key per Sonoconsult The ripper VerifyCD's technical environment Parts of an audio CD How a CD-R is organized Quality Control - CD error categories CD Duplication vs Replication Red Book WAV file manipulation cdripper error with specific drive Adding two seconds of silence at the beginning of the first track Excerpts about Pregap handling from K3b release notes Microsoft's advice: When a CD won't read, or won't read correctly VerifyCD Support Introduction ------------ Small computers today (2007) are putting unprecedented power in the hands of those of us with limited resources, and wonderful new tools in the hands of those with substantial capital. In particular, tools used to record and publish music are far more accessible, powerful, and varied than they were 20 years ago. If you are reading this, you are probably interested in publishing sound in a digital format, such as on CD (Compact Disc.) I will not restrict myself in this document to addressing just the VerifyCD program, wonderful as it is, but to try to address many issues that an audio CD publisher should be aware of. This will give a better context for describing the value and limitations of VerifyCD, and encourage those who are considering publishing sound recordings. Your humble documentation author is K.G.H. Nicholes of Concise Logic, an experienced programmer, relative newbie sound publisher, and enthusiastic VerifyCD user. This document draws on my experience and experiments, VerifyCD's website documentation, internet research, and the VerifyCD support team's answers to my questions. In my office, VerifyCD demo and professional versions) are being run under Windows 98SE on an Athlon 950 CPU system with a Sony CRX-175A1 CDRW (IDE master), a Lite-On LTN-403 secondary (IDE slave) CDROM, and numerous EIDE and Firewire harddrives. The firewire chassis also sometimes hosts various CDRW drives. I am currently working with WAV encoded sound files. This documentation was last updated 03/04/2007. Reviewed by Håkan Sjögren 2007-04-27 VerifyCD's Purpose ------------------ VerifyCD is intended to verify the sound data of a whole audio CD, against a single source file or an ordered set of source files. VerifyCD is exceedingly useful for checking master CDs, destined to go to a CD duplication/replication service for a production run, against their source files. It is also exceedingly useful for checking duplicated CDs against their master's source files. Since it is nit-pickingly digital, VerifyCD can pick out subtle errors in a written CD's data that an ear might not. VerifyCD provides a scrupulous, honest, and fast quality control opionion. VerifyCD Versions ----------------- VerifyCD was first developed in 1996. As of 2006, three versions are available. Starting may 2007 the normal version will be scrapped aand the Professional version be available at a reduced price. The demo version has full professional functionality but is limited to 5 minutes of comparison. It checks the first 5 minutes of an audio file or CD, then stops. If you have larger files to compare, the program runs and gives you progress info until 5 minutes into the file, then stops. Thus, if you are testing the demo version, I recommend you choose test material 5 minutes or shorter, or you won't get a final result on the job. Note that if you are checking a CD, the whole disc is ripped to a WAV before the checking starts, not just the first 5 minutes. This example found an isolated error at about 1 minute in, and managed to resynchronize. Then the comparison was fine for the rest of the 5 minutes: Starting... Reading CD... Comparing I:\TrialApp\VerifyCD\VerifyCD150plain\temp\cd.wav and K:\Barth1.wav First non-0 at file1(0:01:973), file2(0:00:000) DIFFERENCE at file1(1:04:049), file2(1:02:075) Equal again at file1(1:05:049), file2(1:03:075) Time limit for DEMO mode is reached. Comparison stopped. This example found an error right away and never resynchronized: Starting... Reading CD... Comparing C:\VerifyCDdemo\temp\cd.wav and E:\TestFile\20minsAudio.wav First non-0 at file1(0:00:000), file2(0:00:000) DIFFERENCE at file1(0:00:000), file2(0:00:000) Time limit for DEMO mode is reached. Comparison stopped. The Professional version checks a whole CD against one or more source files. VerifyCD Professional can handle several audio file formats; WAV, AU, AIFF, SND and IMG. (This includes Pyramix, Eclipse, and CDRWIN Image files. Bit depths 8, 16, 20 and 24 are supported. Sampling frequency and bit depth must be the same.) Operating VerifyCD ------------------ VerifyCD can check two digital sound files, such as WAVs, against eachother, or it can "rip" a whole CD to a digital sound file and compare that against a WAV. It can do the same with ordered sets of WAVs as well as single WAVs. Sonoconsult calls the two digital sound data sources "sound streams". First, set up whether "Sound stream 1" is an existing File, or must be ripped from an audio disc in the CD Reader. Per Sonoconsult, only the Windows version can read data directly from the CD reader. Mac and Linux users have to rip the CD audio first and point Sound stream 1 at the resulting file. If a File is chosen, the Browse button function provides a typical file search facility. One or more selected files can be "added" from the lefthand directory box to the righthand box displaying the chosen files. Buttons also provide file "remove" (unchoose) functions. (On my system, "Remove All" looks like "Remove ...".) The chosen files can be reordered by selecting one chosen file's name and using the Move Up or Move Down button. (Moves don't work if more than one file is selected.) There is a Filename box that can be used to limit the candidate file list to filenames matching a wildcard-specified name (for example, Song*.wav). If CD Reader is chosen for "Sound stream 1", all system CD reader's model are displayed and you can select the drive you want to use.. (On my system, both Primary IDE devices are harddrives. The secondary IDE master's CD drive is used by VerifyCD. The secondary IDE slave's CD drive is ignored by VerifyCD.) I tried using the Device Manager in the System section of the Control Panel to swap the two CD drives' letters. Even when the master was K: and the slave was J:, only the master was seen by VerifyCD. This limitation is imposed by the cdripper program. If you need to try a different CD drive with VerifyCD, there are two good strategies. You can physically swap another drive in for the one currently being used. Or, you can use a different CD ripper program that supports other drives on the system. (You cannot move VerifyCD to another computer - your Key is "tuned" to the system that generated the registration string for your license key request.) If CD Reader is chosen for Sound stream 1, the CD disc played *must* have two seconds of silence at the beginning of the first track, or VerifyCD cannot cope with it. Since the two seconds of silence is also required by the "Red Book" audio CD standard, this is a reasonable requirement. Per Hakan at Sonoconsult: You can not select a track from a CD since we designed the software to check the complete CD. If something anywhere on the CD is wrong the CD is wrong. There is also nothing like a minor or a major fault. *Any* fault is wrong. The CD going to the factory as a premaster must be 100 % correct. I surmise that a different CD ripper might be used to extract just one track to be checked to a file. Idea included just in case you want to for some reason - e.g. EAC (exactaudiocopy.de). "Sound stream 2" is always a File. The Browse function works as described above. Use the Move buttons to put the files in the same order they are in on the CD (or in Sound stream 1). The WAV (or etc) sound files may reside on a (single) data CDROM disc in another drive. Note that the CDA files visible to the Browse on an audio CD are not suitable - they are not the sound files themselves but merely represent disc structure (housekeeping) information files. I haven't tried it, but I presume that a combination of files on a system harddrive and files on a (single) data CDROM disc in another drive would work fine as well. Even the floppies are useable. The important concept is that you should not need to swap any removable media while the compare is running. Once the sound streams are chosen, the Start button launches the compare process. "Starting..." appears in the status box. If CD Reader is active, "Reading CD..." appears in the status box. The default ripper program (cdripper) reads the CD and creates a digital sound file in the "Temporary directory" specified in Options. (Be sure you have enough free space there.) After cdripper finishes, or immediately upon starting if you are working with two files, text detailing the two sound stream specifications is added, and you will see a time counter above the status box showing progress through the running comparison. An initial synchronization message appears, such as: First non-0 at file1(0:02:000), file2(0:00:000) After that, while the counter is counting, no news is good news. Digital silence is always zeroes. "Silent" areas are not considered errors, and their lengths are ignored between tracks - these are where pure zeros are encountered in the data. This means that variations in the times of silence between tracks (and at the beginning of the first track) is not a problem to the comparison. As Sonoconsult puts it: The use of PREGAP and POSTGAP commands that put silence before or after a track on the CD is supported. This means that the files are considered equal even if silence is inserted anywhere on the CD. Silent areas within tracks are noted ("pause"), but are not considered a reason to "fail" the comparison. If an area of differing non-zero data is encountered, a processing message is output to the status box. VerifyCD tries to resynchronize after an error is found. This may not succeed, especially if a group of errors prevents an exact match from happening quickly. If it is successful, another processing message is output to the status box. Frequently, I have noticed a notification of a very short "pause" (silent area) just at the end of the job. This does not seem to indicate a problem. When the comparison is done, a green OK or red FAILED appears above the status box. An error count is listed for FAILED comparisons. * OK means equal files * OK? means possible equal files but the trailing data after the end of the shortest file has a maximum level above the specified level. (See "Tweaking VerifyCD for your project", below.) * FAILED means incorrect data. Here is a sample of an OK, data-perfect comparison of two files: Comparing E:\Barth_6\Barth6-1.wav and E:\Barth_6\Barth6-1copy.wav First non-0 at file1(0:00:000), file2(0:00:000) Both files ended at file1(3:51:386), file2(3:51:386) Finished at file1(3:51:386), file2(3:51:386). Files are equal. Here is a sample of an OK, data-perfect comparison using the CD Reader: Starting... Reading CD... Comparing E:\cd.wav and L:\BarthWAV\CD1\Barth1.wav;L:\BarthWAV\CD1\Barth1a.wav First non-0 at file1(0:02:000), file2(0:00:000) Pause detected in file2 at 42:05:346. Length 0:00:000. Both files ended at file1(42:07:346), file2(42:05:346) Finished at file1(42:07:346), file2(42:05:346). Files are equal. This job has the "pause" notification I mentioned. The message numbers indicate that the pause is very short and right at the end. Here is a sample of a FAILED comparison. The first 37 minutes verified as data-perfect, then two problem areas were found: Starting... Reading CD... Comparing E:\cd.wav and L:\BarthWAV\CD5\Barth5.wav;L:\BarthWAV\CD5\Barth5a.wav First non-0 at file1(0:02:000), file2(0:00:000) DIFFERENCE at file1(38:08:332), file2(38:06:331) Equal again at file1(38:09:332), file2(38:07:331) DIFFERENCE at file1(38:55:229), file2(38:53:227) Equal again at file1(38:56:229), file2(38:54:227) DIFFERENCE at file1(42:29:783), file2(42:27:780) Equal again at file1(42:30:783), file2(42:28:780) DIFFERENCE at file1(42:32:159), file2(42:30:157) Equal again at file1(42:33:851), file2(42:31:849) DIFFERENCE at file1(42:37:396), file2(42:35:394) Equal again at file1(42:38:396), file2(42:36:394) Pause detected in file2 at 49:26:959. Length 0:00:000. Both files ended at file1(49:28:960), file2(49:26:960) Finished at file1(49:28:960), file2(49:26:960). Files are NOT equal (difference count is 5). This was a duplicated CDR. The whole batch of 100 had exactly the same errors. I listened to the differing areas carefully (at 38 and 42 minutes into the audio), and in fact it sounded fine. I decided it was OK to release the duplicates for sale. (But I plan to use a different duplication service next time.) Here is an example of a FAILED comparison that had enough differences that it was not able to resynchronize after the first two seconds: Starting... Reading CD... Comparing E:\cd.wav and L:\BarthWAV\CD7\Barth7-11.wav;L:\BarthWAV\CD7\Barth7-12.wav; L:\BarthWAV\CD7\Barth7-13.wav;L:\BarthWAV\CD7\Barth7a-14.wav; L:\BarthWAV\CD7\Barth7a-15.wav;L:\BarthWAV\CD7\Barth7a-16.wav First non-0 at file1(0:01:690), file2(0:00:000) DIFFERENCE at file1(0:04:146), file2(0:02:456) File2 ended before file1 at file1(40:55:970), file2(40:54:280). The remaining part of file1 (duration: 0:00:309, samples: 13643) is NOT silence. The peak sample in the remaining part is 2% or -36 dB. Finished at file1(40:56:280), file2(40:54:280). Files are NOT equal (difference count is 2). Ear testing found some muffled areas in the audio. Further testing revealed that these duplicated CDRs would not play on some drives. I failed the batch. If you want to compare two CDs you would need to rip one of them to your harddisk first to use as the Sound stream 2 file. Sonoconsult suggests exactaudiocopy software for this purpose. (http://www.exactaudiocopy.de) To record your comparison results for later reference, there are two methods. To copy-and-paste the text, click in the status box, Ctrl-A to select all the messages, Ctrl-C to copy them. Open an editor, click in the document, and Ctrl-V to paste the messages to your document. A text file (default name VerifyCD.log) also contains the most recent run's messages. It is located in the directory specified in Options. You can change the name of the file by entering it in the Optional ID box above the status message box. Tweaking VerifyCD for your project ---------------------------------- The Options button provides access to setup for the default location the Browse opens to for both sound streams. Having the browse open up looking at a useful/convenient folder (directory) can save a lot of time and hassle. Explaination of other Options per Sonoconsult: When reading directly from CD the default behavior is to read each block once. You can specify in this field that VerifyCD should read each block more than once until two block reads are the same. All drives have a few samples of offset between actual audio data and the start/end information of tracks and is reported at the start of each comparison. Because of such offset the two files might be reported having unequal lengths. If trailing samples in the longer file are zeroes, VerifyCD will accept this as correct but if not zero, VerifyCD will report the length of the tail and the max level. You can, in this bottom field, specify your maximum acceptable level. Sonoconsult's description of VerifyCD's use in creating an Audio Master ----------------------------------------------------------------------- 1. Listen to the final mixed master sound file in your computer. Use one large file for the whole CD. 2. Burn the premaster using your favorite software, e.g. CDRWIN from www.goldenhawk.com or EAC from exactaudiocopy.de. 3. Run VerifyCD. If you get the message "Equal files", the sound data on the CD is binary bit for bit equal to the master file. Limitation: Each track must be longer than 2 seconds. This is because VerifyCD will try to resync data after a difference is found and will need approximately 1 second of data to do this. Most glassmastering plants run further tests to verify Redbook compliance before making the glassmaster. 4. Make a copy of the CD premaster. 5. Verify the PQ, ISRC and MSN codes using your CD burning or CD ripping utility. Installation/licensing ---------------------- I'm betting that installing VerifyCD under WinXP is smooth and sets up a shortcut for use. Versions for Win32 use a .MSI installer that won't cooperate with Win98 or W98SE. When run, they complain: Installer Information VerifyCd cannot be installed on Windows 98. When I encountered this, sonoconsult support person Hakan Sjogren replied to my emailed inquiry (support@sonoconsult.se) promptly. No problem; the "Mac etc" download version unzips to useful files and seems to run fine on my W98SE system. I used WinZip to extract the files to a directory I created. I then created a shortcut. I right-clicked an empty spot on my desktop, chose New and clicked Shortcut. I clicked the Browse button under the Command line field. I found and selected VerifyCD.exe in the folder I extracted it to. Clicked Open, clicked Next. Changed the name from VerifyCD.exe to VerifyCD. Clicked Finish to create my shortcut. You can put the VerifyCD file tree (files and subdirectories of files) in any directory. You can even have multiple versions on the same machine, as long as they are in different directories. VerifyCD does not put any information in the registry, so its directory's drive and name can be easily changed. You just have to update the shortcut's Target and Start In fields (right-click the shortcut, choose Properties) to match. As an anti-piracy measure, VerifyCD uses a machine-specific licensing key. You have to install the demo on the machine you want your live software on. Then run the demo and use the Enter Data for License Key function to request a registration string. Submit that string with your payment online, and receive the key to remove the demo hobble by email. Run VerifyCD again and click the Set New License Key button. Paste in the key you received. There are good instructions for this process online. (I also copied the current online version to a section below, Acquiring and using your License Key per Sonoconsult.) If you need to switch out your machine, or if you upgrade your OS or processor, email Sonoconsult's with your new registration string to get a new key. Your license is still good. I have verified experimentally that you can swap out your CDROM/CDR/CDRW drive in the original registered machine without affecting the license. Thank you, Sonoconsult. A welcome assurance from Sonoconsult: The license key will be locked to the user and not to the box, each license fee grants you the right to use one copy on any one hardware product, see http://www.sonoconsult.se/VerifyCD/doc/LICENSE.htm for further details. Solving another known error per Sonoconsult: "No JVM could be found on your system. Please define EXE4J_JAVA_HOME to point to an installed JDK or JRE" Solution: Download Java from http://java.sun.com or download a verifyCD version including Java and reinstall VerifyCD. Acquiring and using your License Key per Sonoconsult ---------------------------------------------------- 1. Install the demo version on your computer, see installation documentation on http://sonoconsult.se/VerifyCD for instructions. Use the demo version which is a full version but limited to 5 min comparison. When you have decided to buy, continue as described below. 2. Start VerifyCD. You will see four buttons at the top of the window Enter Data for License Key - Set New License Key- Options - Help - About 3. Hit the "Enter Data for License Key" button. Enter data in all fields, then hit the "Calculate License Key Data" button. You will now get a long string in the window below the button. Copy this string into your clipboard. Click in the white box containing the string and use Ctrl-A to highlight the whole string and Ctrl-C to copy it to the clipboard. You will paste this information later when you make you payment. (Mac users use the apple key instead of the Ctrl key). 4. Purchase at the following Web address: http://SonoConsult.se/VerifyCD . Under the header Additional Ordering Information you are asked to paste the key request string. Do this by pasting the string you now have in your clipboard by clicking in the field and pressing Ctrl-V. This should make the long string which you got previously appear here. This string contains all the information we need to generate your license key which will be emailed to you. 5. You will get a payment confirmation email from share-it. 6. You will be sent a new string - the license string by email. Allow 48 hours for this email to arrive. 7. Start VerifyCD again and hit the "Set New License Key" button. 8. Paste the key you received after finalizing your purchase and hit the "Set key" button. You should now get new values for all the fields corresponding to what you entered above when collecting environment data. IMPORTANT: Save the license key string in a text file and store it in a safe place. Your license is now bound to yourself and your computer. 9. Your program is now ready to use. 10. The license key is locked to the user and not to the box, each license fee grants you the right to use one copy on any one hardware product, see http://www.sonoconsult.se/VerifyCD/doc/LICENSE.htm for further details. The ripper ---------- VerifyCD uses cdripper.exe to extract from audio CDs to WAV files. VerifyCD's technical environment -------------------------------- As an old-school tech/programmer, I love how this program is made, efficient and tidy. That it is multi-platform is a further advantage. VerifyCD is 100% written in Java and will therefore run on all Java-supported platforms (Java 1.3 or higher) including PC, MAC, Linux and more. VerifyCD is one and only one file (VerifyCD.jar) with a size less than 100 Kb. No other files are installed into system directories; no environment variables need to be set and the system registry is not touched. Uninstallation is normally done using the uninstall programs in the control panel. Parts of an audio CD -------------------- An audio CD has data areas called tracks, and housekeeping information that informs the CDROM reading device about the disc's structure. The track audio data is encoded in a way very similar to WAV files. ("The only difference between a "raw" 44.1KHz 16-bit stereo WAV file and CD audio is the byte ordering.") The most basic and important housekeeping area is the TOC, Table Of Contents. Every CD has a TOC. The TOC describes the CD layout, and the TOC of the first (or only) session is located in the grooves closest to the disc's center hole, "before" the first audio track. The TOC provides information about the lengths of the tracks, and their physical position on the disc. Additional housekeeping areas may be present, for text info such as track titles, and for additional sessions' TOCs on a multi-session CD. A text/program/video/multimedia datafile area may also be present on a multi-mode CD. Audio data areas have error-correction data associated with them, and track time counter information. On a multi-session CD, every session has it's own TOC containing the layout of that session PLUS the layout of all previous sessions, recorded in the lead-in of that particular session. Stereo component and portable CD players generally only read the innermost, original TOC, and ignore (or are confused by) additional information. How a CD-R is organized ----------------------- CD-R discs are written from the center toward the edge. They have pre-formed grooves that the writer follows. CD-R blanks get holes punched in their sensitive layer by the laser ("burned"), CDRW blanks have a light-sensitive layer that merely changes state, so that it can be re-altered later. Many CD reader devices cannot read CDRW discs, most can read audio CD-Rs. The oldest CD players are reportedly least able to read CD-Rs. There is lots of good information online, especially at http://www.cdrfaq.org/. Much of the below information in this section is taken or edited from: http://www.cdrfaq.org/faq.html http://www.cdrfaq.org/faq02.html A single-session disc has three basic regions: the lead-in, which has the Table of Contents (or TOC); the program area, with the data and/or audio tracks; and the lead-out, which is filled with zeroes and provides padding at the end of the disc. An "open" single-session disc doesn't yet have the lead-in or lead-out written. If you write data to a disc and leave the session open, the TOC -- which tells the CD player or CD-ROM drive where the tracks are -- is written into a separate area called the Program Memory Area, or PMA. CD recorders are the only devices that know to look at the PMA. If you close the current session and open a new one, the lead-in and lead-out of the current session will be written. A TOC will be written in the current lead-in that points to the eventual TOC of the next session. This process is repeated for every closed session, resulting in a chain of links from one lead-in area to the next. Typical audio CD players don't know about chasing TOC links, so they can only see tracks in the first session. Most modern computer CDROM drives can handle multiple session information. A CD-R disc that you can add data to is "open". All data is written into the current session. When you have finished writing, you close the session. If you want to make a multisession disc, you open a new session at the same time. If you don't open a new session then, you can't open one later, which means that it's impossible to add more data to the CD-R. The entire disc is considered "closed". The process of changing a session from "open" to "closed" is called "finalizing", "fixating", or just plain "closing" the session. When you close the last session, you have finalized, fixated, or closed the disc. Some drives won't read an open disc. When the session is finalized, the TOC is written in the lead-in area, enabling other devices to recognize the disc. DAO (Disk At Once) - Disc-at-once (DAO) writes the entire CD in one operation and closes (finalizes) the disc. The lead-in is written at the very start of the process, because the contents of the TOC are already known. TAO (Track At Once) - Track-at-once (TAO) allows individual tracks to be written in separate operations. Gaps between tracks vary, and can contain spurious noise. CD masters should not be recorded in track-at-once mode, because the gaps between tracks will show up as errors. SAO (Session At Once) - Session-at-once (SAO) recording gives you disc-at-once control over the gaps between tracks, but allows you to leave the disc open. Problem-solving: If you're using certain versions of Windows, the Auto Insert Notification feature will "discover" the CD-R as soon as the TOC is written. This can cause the write process to fail, which is why Windows software automatically enables and disables AIN as needed. Otherwise, if recording in track-at-once mode, it will fail during finalization; in disc-at-once mode, it will fail near the beginning of the write process. In both cases, test writes will succeed, because the TOC doesn't get written during a test pass. Yamaha developed Audio Master Quality Recording to compensate for higher "jitter" in recorded CDs. This jitter is time-base error. It's a distortion of the timing in which the '1's and '0's arrive at their destination. This doesn't affect extraction of audio, but is audible when listening to a CD. The digital signal is read from a CD via an analog process: bouncing a laser off of "pits" and "lands" on a CD. Various factors can prevent the signals from arriving at the right place at exactly the right time. High-end CD players can correct these anomalies, but many don't. AMQ extends the length of the pits and lands on the CD in an attempt to produce a more stable signal. This reduces the recordable length of the CD -- a 74-minute disc only holds 63 -- but produces noticeably improved audio (says Yamaha). The process works because CD players automatically adjust the rotation speed. Yamaha's explanation: http://www.yamaha.ca/computer/cp_AudioMQR.asp There are 8 subcode channels, labeled P,Q,R,S,T,U,V,W, or sometimes "P-W" for short. (The ECMA-130 standard refers to subcode bytes as "Control bytes".) Every frame contains one byte of subcode data, and each byte holds 1 bit of P, 1 of Q, and so on. The bytes from 98 consecutive frames are combined to form a subcode "section". The first two bits in each channel are used for synchronization, leaving 96 bits of useful data per channel (which is where RAW DAO-96 gets its name). The P and Q channels are defined by the CD audio standard. (They are unrelated to the P and Q parity fields.) The P channel can be used to find the start of a track, but in practice most devices use the more sophisticated Q channel. Q contains four chunks of information: control (4 bits), address (4 bits), Q data (72 bits), and an EDC (16-bit CRC). The control bits determine whether the track holds audio or data, the number of audio channels (stereo or quadraphonic), and specifies the Digital Copy Permitted and Pre-emphasis flags. The address bits determine the format of the Q data section. Address mode 1 holds information about tracks, mode 2 holds a catalog number (such as a UPC code, constant for an entire disc), and mode 3 contains the ISRC (International Standard Recording Code, constant for a given track but may change with each track). A disc has three main regions: the lead-in area, the program area, and the lead-out area. Subcode Q mode 1 data in the lead-in is used to hold the table of contents (TOC) for the disc. The TOC is repeated continuously in the lead-in area in case of damage (remember, no CIRC encoding on subcode channels). In the program and lead-out area, mode 1 contains track numbers, index numbers, time within the current track, and absolute time. Index 0 marks the start of a pregap (pause) before the audio in a track begins, index 1 marks the start of the music, and indexes 2 through 99 are usually not set but can be added if desired. The ability to specify track and index markers when writing a Red Book audio CD is often referred to as "PQ editing" because that information is contained in the P and Q subcodes. Subcode channels R through W are not defined by the CD standard, except to say that they should be set entirely to zero if not used. They're currently used for CD+G (e.g. Karaoke) discs, CD-Text, and some forms of copy protection. It is interesting to note that, while bytes from 98 consecutive frames are used to create a subcode "section", those frames don't have to be from a single sector. It's possible for a subcode section to start in one sector and end in the next. Videos sold on DVD usually have region coding that prevents them from working on players in other countries. No such restriction is possible in CD formats. Audio CDs, CD-ROMs, and VideoCDs will work equally well in any part of the world. Compact Disc technology rocks worldwide. Quality Control - CD error categories ------------------------------------- Audio projects are blooming all over. Small computers are putting the power to do audio projects on CD (compact disc) into many creative hands. Publishing a CD can be downright cheap - in 2007, 100 CD-R duplicates with beautiful labels cost less than $200USD. The digital sound and package artwork can be edited on almost any modern small computer, with modestly-priced software tools. The first step in publication is creating a master disc to be duplicated. There are lots of programs available to write audio CDs. It is important that the master CDs are as flawless as possible. Check and recheck the original files - sound levels should be reasonable and they should sound just right. Prefer a CD writer drive that has proven reliable. Use good quality CD-R blanks. Finally, for peace of mind, double-check the accuracy of each written master. Automating the verification process makes it quicker, and is likely to catch more subtle problems than our ears can. That's why I use VerifyCD. Data errors may be present in the track audio data. This will be caught by a VerifyCD comparison. VerifyCD reads the data in the track independent of what the indexes say. VerifyCD verifies the audio part of the CD-audio, not the indexes. VerifyCD is much more sensitive to these errors than our ears. Since the audio data constitutes most of the data on the CD, its quality may be an indicator of the quality of the housekeeping data. However, good-quality error-corrected sound data is not a guarantee of good-quality non-error-corrected housekeeping data. Data errors may be present in the housekeeping data. This may "accidentally" be caught by VerifyCD, if revealed by the CD drive/OS driver/cdripper having trouble reading the CD. Errors in any text on the CD will not be caught by VerifyCD. Testing the CDs for playability on a variety of different players and drives will help diagnose housekeeping information errors. In my experience, devices that only read (portables, stereo components, and CDROM drives) will happily read many defective CDs that writing (CDRW, CDR) drives have trouble with. I have acquired a variety of CDRW drives that I mount in my Firewire chassis to test CDs with. On a Windows system with Auto Insert Notification active, a good CD when inserted should A) be promptly identified as an audio CD, B) promptly show a correct track list in Windows Media Player, and C) sound right when it plays. Be careful when testing CDs in DVD readers - not all DVD drives are designed to read CDs also. The ones that don't can damage a CD-R trying to read it as a DVD, by using excessive laser strength. I advise checking with the Control Panel device list to make sure an unknown drive is designed to read CDs *before* putting a CD into the drawer. Difficulty playing a CD may be the fault of: A) the current state of the machine (try a fresh boot), or B) configuration of the OS (operating system), C) the drive's driver software (some drives benefit from specialized drivers), D) the drive's own internal programming (some have updates available online), E) the drive's state of cleanliness, F) the condition of the drive's laser (strength weakens gradually with use, best estimate of reliable lifespan is about 100,000 discs written), G) cleanliness and surface smoothness of the CD and H) data recorded on the CD itself. Sometimes, more than one problem coincides. Irregularities in the spacing of the pits on the CD will not be caught by VerifyCD. If problematic, they should be audible to a critical listen by a human engineer. VerifyCD gives me more peace of mind that my masters, and copies, are adequate. If they sound OK, and VerifyCD says they match the source files, and they play OK on various drives and devices, I can ship the job with confidence. CD Duplication vs Replication ----------------------------- Duplication is the writing of CD-R blanks with information read from a master CD. Duplication is available in small quantities for about $200 for 100 duplicates. Duplication equipment is relatively inexpensive. Some CD players do not play CD-Rs, though most modern ones do. Master CDs submitted for duplication are usually not checked for quality by the duplicator. Replication is the manufacture of CDs in mass quantity. The manufacturing process uses a template ("glass master" process) to create plastic discs with the track grooves and data pits simultaneously. A minimum order is generally 1000, and will probably cost about $1 each. Replication equipment is expensive, and creating the template is also costly. Replicated CDs are what most music stores sell, and they are expected to play on any CD player, even the oldest ones. The glassmastering plant often runs a quality check on your original master CD before creating the template, measuring error rate and pit geometry, so you may refer this part of the testing to them. Most radio stations require replicated CDs for consideration on their playlist. Red Book -------- The Red Book standard specifies the physical and data characteristics of commercial CDs. CD players are designed to play Compact Discs adhering to these rules. It is hard to find out what the rules are - a copy of the Red Book is expensive. The rules include physical criteria like pit depth, and information criteria like how the data and error correction information are laid out on the disc. The 2 second rule (two seconds of silent pregap before data at Track 1 start) is specified in the CD standard (red book). The Red Book prohibits tracks shorter than 4 seconds. You can have up to 99 tracks on one CD. The track number is stored as a two-digit decimal number. Tracks must be at least 4 seconds long according to the standard. In practice, CD recorders have different notions of how short a track can be, but most recorders will refuse to write a track shorter than one second. The Audio CD standard (Red book) describes audio in the first session only. FYI: negative track (thing) by holloway Thu Jul 13 2000 at 8:32:21 A form of hidden track in which audio is recorded prior to the start of a CD. It's accessed by rewinding to before the start. Aside from testing each of your CDs individually, what are the symptoms of negative tracks, eh? Read the CD's small print to see if it has a disclaimer along the lines of "CD doesn't fully conform to the Philips Red Book standard". This will usually be printed somewhere on the outer CD -- to warn consumers with older, un-compatible, CD players - ones that don't play this broken standard. WAV file manipulation --------------------- Concatenating WAVs with "COPY A.wav + B.wav C.wav" does not produce a useable C.wav. Since WAV files start with header information, this makes sense. For more info about WAV file structure, see: http://www.sonicspot.com/guide/wavefiles.html cdripper error with specific drive ---------------------------------- My Plextor PX-W1210TA CDRW drive is very finicky about the CDs it reads. For a while I had it installed as my primary drive in the VerifyCD software's system. Some discs caused cdripper to crash with this drive. The crash looked like this: Windows An exception 0D has occurred at 0028:C182C718 in VxD APIX(02) + 000004B8. This was called from 0028:C182C6DF in VxD APIX(02) + 0000047F. It may be possible to continue normally. * Press any key to attempt to continue. * Press CTRL+ALT+DEL to restart your computer. You will lose any unsaved information in all applications. Press any key to continue Replacing the drive fixed the crash problem. I still use the Plextor, but not with VerifyCD. I use it in my Firewire chassis, to test for marginally reading CDs. Adding two seconds of silence at the beginning of the first track ----------------------------------------------------------------- The 2 second rule (pregap before data in Track1 starts) is specified in the CD standard (red book) and has always been. Thus most CD burning programs include it. Some CD burning software also by default includes a 2 second gap between songs. I currently use Linux CDR/sound utility K3b 0.12.17 running under the KDE GUI (graphical user interface) on a Slackware Linux machine. My first audio CD publication is a 7-audio-disc set of historic lectures from the early 1960s. Here's how I add two seconds of silence at the beginning of the first track on each of my masters: Right-click the first track and "Add silence". That adds 2 seconds of silence to the end of the track. Click and drag the silence's green item dot from below to above the track's wav file's green item dot. Now the silence is listed first and will be written first. Excerpts about Pregap handling from K3b release notes ----------------------------------------------------- 01.03.2004 K3b 0.11.6 + i18n package The new Pregap handling Up to K3b 0.11 pregaps in an audio project were created as additional silence. That was not the best way to handle it. K3b 0.12 treats pregaps as what they really are: simple index ranges. The pregap on an audio CD does not influence the music on it in any way (if burned with the DAO writing mode which is the default in K3b) except that your Hifi CD Player will count backwards on audio blocks with an index of -1 (which is the index for the pregap). So now K3b uses the last 2 seconds of a track as the default pregap like it is defined in the Red book standard. If you want additional silence between the tracks like it was possible with older K3b versions use the silence sources described above. 13.06.2005 K3b 0.12 The main focus of this release is clearly the audio project. It has been nearly completely rewritten. As a result one can now merge tracks, split them, or add silence at the end or the beginning of a track. The unusual handling of pregaps in older K3b versions is gone. Now the unexperienced user does not need to bother with pregaps at all. K3b does not add two second pregaps by default anymore. It now works like it should: the pregap is simply a property of the track and if one wants to add a real gap there is always the silence source which can be added whereever needed. Microsoft's advice: When a CD won't read, or won't read correctly ------------------------------------------------------------------ Here are some tips for troubleshooting CD-ROM, CD-R, and CD-RW disc read issues under Windows 95, Windows 98, and Windows Millennium. A drive may read most but not all discs, but this alone does not confirm that a disc is bad; the drive could be having a marginal problem. Example problems: The CD Disc label does not appear in My Computer, or the contents of the disc will not display. This troubleshooting list is intended to be considered in order. 1) Check the problem disc for deformation and scratches, especially non-radial ones. 2) Clean the CD-ROM. A) Use a disc cleaning kit, or gently clean the non-label side (usually plain silver, gold, blue, or green) of the disc with a soft, lint-free cloth. Cloths sold for cleaning optics are ideal. Paper towel or tissue can scratch the plastic and cause permanent damage. Wipe radially from the center of the disc outward. Do not use a circular motion. B) Wash the disc in lukewarm water and mild detergent and rinse thoroughly, or use a commercial CD cleaning solution per package directions. Dry the disc before putting it into the drive. 3) Try the CD-ROM in another drive, to help figure out whether the problem is with the disc or the drive. 4) Clean the disc drive using a commercial CD-ROM drive cleaning kit. If you don't have one, skip this step until later. (My non-Microsoft advice for techies: Remove the drive, open its case, blow out the dust. Very gently clean the laser lens with swabs and some anti-static optics fluid, inspect. Wipe the CD tray with a damp cloth. Reassemble and reinstall.) 5) Other running programs may interfere with the reading of the disc. Anti-virus, firewall and anti-crash programs that run in the background may be a problem. 0. My advice - be smart - If you are connected to DSL or a LAN, engage your firewall's "internet lock" and leave it running, or remove the cable from the computer before shutting down the firewall. 1. Close down programs running in windows on the desktop. 2. Right-click each icon in the Taskbar area (near the Windows clock), then click Exit, Quit, Close, Disable, etc if available. 3. Press CTRL+ALT+DEL to display the Close Program window. If any program other than Explorer is listed, click it, then click Remove. Repeat this step until all programs except Explorer have been removed. Explorer, the Windows user interface, is always needed to see a CDROM. (This procedure is too radical for WinXP.) 6) The Microsoft Knowledge Base (http://support.microsoft.com/) or the internet may have relevant info about your brand and model of CD-ROM drive, your CD-R or CD/RW recording software, or known interactions between them. 7) Check for Drive Firmware or Driver Updates Check for relevant driver or utility updates for your disc drive or computer. These may resolve problems where the drive can read most but not all discs. 8) Under Windows 95 or Windows 98, make sure you are using protected mode (32-bit) drivers for your CD-ROM or DVD drive. Start /Settings /Control Panel /System /Performance. Check that File System says 32-bit. In the CDROM section of Device Manager (also in System), right-click the drive and choose properties. Select the Driver tab. MS-DOS disc drivers are real mode or 16-bit drivers, and may not be able to read certain files on the CD-ROM that only work correctly with protected-mode drivers.' For info on protected-mode drivers for CD drives, see the Microsoft Knowledge Base article 151634, Protected-Mode CD-ROM Drive Support in Windows (http://support.microsoft.com/kb/151634/EN-US/) Close System, close Control Panel. 9) Enable/Disable UDF Support. If you are using Windows 98 or Windows Me, disable UDF file system handling temporarily. Start /Run /msconfig. Click the Advanced button. Check (or uncheck) Disable UDF File System, click OK. Restart. Test reading the CDROM. Generally, UDF should be enabled if the drive supports it. Some drives can't read discs that only use the UDF file system. 10) Disable DMA for the Drive. Start /Settings /Control Panel /System /Device Manager Click View Devices By Type if they aren't already grouped that way. Click the plus sign (+) next to CDROM to see those devices. Right-click the CD-ROM drive that you want to change, and choose Properties. On the Settings tab, clear the DMA check box, and click Close. Close Control Panel, restart the computer. 11) Reduce Drive Caching. Start /Settings /Control Panel /System /Performance Click the File System button. Choose CDROM tab. Slide the Supplemental Cache Size to the Small position. In the Optimize Access Pattern For dropdown, choose NoRead-Ahead. Click OK, and restart. 12) Disable Auto-Insert Notification. This prevents Windows for checking the CDROM for a new occupant disc and firing it up automatically. To disable Auto-Insert Notification: Start /Settings /Control Panel /System /Device Manager Click View Devices By Type if they aren't already grouped that way. Click the plus sign (+) next to CDROM to see those devices. Right-click the CD-ROM drive that you want to change, and choose Properties. Choose the Settings tab. Clear the Auto Insert Notification check box. OK, OK, close Control Panel, restart. 13) Remove Duplicate Drives Remove any duplicate CD-ROM drives being loaded by Windows. To do this: Start /Settings /Control Panel /System /Device Manager Click View Devices By Type if they aren't already grouped that way. Click the plus sign (+) next to CDROM to see those devices. Check that there is only one entry for each CD drive your machine has installed. Note down the properties of each drive listed. Close System and Control Panel. Restart in Safe Mode: Windows 95: When you see the "Starting Windows 95" message, press the F8 key, and then select Safe Mode on the Startup menu. Windows 98 and Windows Millennium Edition: press and hold down the CTRL key when your computer completes the Power On Self Test (POST), and then select Safe Mode on the Startup menu. When Windows starts in Safe mode, click OK to see the desktop. Go back to seeing the Device Manager's CDROM section. Look for changes. Devices that were not in the list earlier should be removed. If there are extra copies of a device, remove all but the one that exactly matches the properties you noted on a regular boot. Close System, close Control Panel, restart. 14) CD drive lasers become weaker with extended use, and will eventually need to be replaced. More help from Microsoft's Knowledge Base: MS' article for 95/98/Me (http://support.microsoft.com/kb/218617) Troubleshooting CD-ROM Problems in Windows NT126380 (http://support.microsoft.com/kb/126380/EN-US/) Troubleshooting CD-ROM Problems in Windows XP 314096 (http://support.microsoft.com/kb/314096/EN-US/) This section updated Jan 28 2007 by KGHN. VerifyCD Support ---------------- Help information and explanation of the fields are given in the Help.htm file in the doc folder. Help on setting the options is given in the OptionsHelp.htm. Support http://sonoconsult.se/VerifyCD/doc/Help.htm Download http://sonoconsult.se/VerifyCD/download.htm email support for VerifyCD is available: support@sonoconsult.se EOF: KatesDoc.txt updated 03/04/2007 by KGH Nicholes Update by Håkan Sjögren 2007-04-27 |