Ripping off recordings DIGITAL AUDIO EXTRACTION DO’S, DON’TS AND DO’ERS

Ripping off recordings DIGITAL AUDIO EXTRACTION DO’S, DON’TS AND DO’ERS – Statistical Data Included

Robert A. Starrett

We all know that the Red Book–the original CD standard–defines CD-Audio, and that the compact disc for one purpose: to store and play music in digital format. Designed initially to be nothing more or less than a universal delivery medium for music digitized at 44,100 samples per second (44.1KHz) and in a range of 65,536 possible values (16 bits), Red Book, or Compact Disc-Digital Audio (CD-DA), was defined by Philips N.V. and Sony Corporation in 1980. It was an overwhelming–if not quite instant–success, and today, with inexpensive tools and recorders, the average consumer can do much more with audio CDs than play them back on their stereo systems. Technology available today–though internally complex–renders quite simple, accessible, and relatively inexpensive the enticing prospect of extracting and re-recording the original Red Book data to make custom compilation CDs of any music enthusiast’s favorite tunes.

The downside of it all is that the careless, the pirate, and the criminal take great advantage of these inexpensive tools and recorders for the illegal distribution of compilations of copyrighted songs or complete album copies. This musical contraband can be stored and distributed on CD-R, by pressed disc, or in MP3 format, and sold at discounts, leaving the artist, the recording company, and the songwriter without royalties–in essence, without payment for their work. But audio extraction also supports not-for-profit private pleasures, of course, and plays a key role in the back-end infrastructure of today’s increasingly popular Web-driven custom audio CD services. While using the same enabling technology as the pirates and bootleggers, such Web-based businesses as customdisc.com and supersonicboom.com are upstanding, royalty-paying enterprises who offer alternate music distribution (and technology) models fully approved and accredited by the music industry, powers-that-be.

Whatever your purpose, accurately extracting a Red Book track from a CD has always been more challenging than copying a file from a CD-ROM to a hard drive. Red Book tracks are not files, per se. They are made up of a bunch of data that is meant to stream, and within the stream there is more than music. The stream itself is not a straight stream, it is interleaved; that is, portions that naturally follow each other in a song do not follow each other on the disc itself. You can easily record an analog version of a song from your computer through your sound card to hard disk, or record from your CD player to a tape deck, but getting a digital copy of the music that is on the disc, and getting a good one–let alone a perfect one–is another story altogether.

WHY EXTRACTION?

There are many reasons to move audio from CDs to hard disk. Some would argue that the most common is for piracy purposes, although that debate is better left for another forum. Here we are just going to examine the process of Digital Audio Extraction, also known generally and unfortunately by the word “ripping.”

Digital Audio Extraction (DAE) is the process of moving a Red Book track on a CD, usually music, from that CD to a hard drive or other storage medium by creating a file in any number of formats, although the most popular one is the WAV format. There are many possible purposes for which one might want to move the track into a file: to edit the sound, to rerecord it to another disc for a compilation disc, to further manipulate the file by compressing it into an MP3 file or a Yamaha VQ file, or to convert it to a lower-quality WAV file to use as a system sound, to name just a few.

Many CD recording software packages contain a digital audio extraction function. This functionality has been around as long as recording software. But only recently has it become so popular a feature that there are now many specialized programs that do nothing but extract audio. Recent years have seen many recording software manufacturers releasing new versions of their programs with enhanced audio features or producing separate or companion programs for audio extraction, manipulation, and recording.

LIKE PULLING TEETH?

Why is it so hard to get good extraction? The difficulties are inherent in the way audio discs are written. Data on an audio disc is organized into frames in order to ensure a constant read rate. Each frame consists of 24 bytes of user data, plus synchronization, error correction, and control and display bits. One of the first things that it is crucial to understand about CDs is that its data is not arranged in distinct physical units. Instead, the data in one frame is interleaved with the data in many other frames so that a scratch or defect in the disc will not destroy a single frame beyond correction. Rather, a scratch will destroy a small portion of many frames, all of which can probably be recovered.

A Red Book disc itself is divided into three areas: Lead In, Program, and Lead Out. Each track’s location, or address, is recorded in the disc’s Table of Contents (TOC), which is stored in the Lead In area of every disc. Because pressed CDs are read-only, the number and location of the audio tracks to be recorded are known in advance, and the final TOC is created on the glass master in advance of the actual audio data. An audio disc can contain up to 99 tracks, which are stored in the Program area. Following the Program area is the Lead Out area, which is simply 90 seconds of silence, or blank sectors. Encoding a Lead Out area on an audio disc lets CD-Audio players know that the music stream has ended.

So an audio disc’s TOC, much like a book’s, is a good resource for knowing what’s where, but can’t always lead the reader to the right spot. If “How to Make an Audio CD” is a chapter in a book that begins on page 43, that doesn’t necessarily tell you where the part about actually recording the CD is as opposed to the other steps in the process (unless it’s, say, a sub-indexed science textbook). Likewise, the Table of Contents on an audio CD tells the CD reader about where the song starts, but, unlike a CD-ROM with data on it, it does not tell it exactly where it starts.

Audio discs were designed to be read sequentially, in real time, with the digital data converted to an analog signal that would be played through a stereo’s speakers. There was no need to have data on the disc to pinpoint the exact location of the beginning of a song. It is good enough just to get close. That extra data containing an exact starting address for each song takes up space that could otherwise be used for musical data. Since CD-Audio data is stored on the disc in a different form than computer data, accurate extraction can be a difficult task. The 2,048 bytes of user data in each 2,352-byte CD-ROM sector can be accessed exactly because the header information in each sector contains the precise address of the data block.

An audio block, on the other hand, contains 2,352 bytes in each physical block and all of these bytes are used for audio data. No header exists; there is no information in the block that allows for the exact positioning of a read head over a specific block. To address an audio block, a drive must use the Q subcode. The Q subcode only provides audio positioning to within [+ or -] 1 second of the actual block address. When addressing an audio block, a CD-ROM drive moves the read head to a position close to the requested block, then compares the Q subcode to the block address being sought. The Q subcode references the minute, second, and frames relative to the start of the track and also the Absolute time, that is, the time in minutes, seconds, and frames relative to the whole of the disc.

When requested to seek an audio sector, the drive starts reading, then compares the Q subcode information to the block address being sought. The drive begins transferring data when a Q subcode address that is close to the desired block address is located. CD-ROM drives many times only seek an audio address that is within [+ or -] four Q subcode addresses of the address being sought ([+ or -] 4/75th of a second in playback time). In that case, a read request could return any one of nine blocks. This is why extraction is not an exact science. Clicks and pops in the extracted files are many times caused by this inexact positioning.

THE ROLE OF READERS

Anyone who has done any significant amount of Digital Audio Extraction is well-aware that some CD-ROM drives and recorders perform the task well, while others do poorly or will not extract at all. Traditionally, SCSI drives have been better at extraction than ATAPI drives. Some lower-cost drives are less likely to perform the task well, while higher-end, namebrand drives usually perform adequately.

Today’s best-selling drives run the gamut of DAE capabilities. Plextor leads the way with its 40X UltraPlex drives and its DAE-optimized driver software. There is no intention here to list which drives perform well and which do not. There are simply too many variables to consider that go well beyond a drive’s innate capabilities. Many factors affect a drive’s DAE performance, including system settings, software used, disc condition, and drive condition. CD-ROM drives passed into the commodity product domain years ago, and with myriad manufacturers continuing to improve the speed and audio extraction capabilities of their drives, frequently if irregularly, any listing presented here would be obsolete by the time you read it.

DIGITAL AUDIO EXTRACTION DEFINITIONS

There is a great deal of software available, mostly as online shareware or freeware, that is specifically designed for digital audio extraction. The differences between the various tools are deep in the details, and those details are peculiar to the digital audio extraction technology niche. So when using specialized extraction software, it is helpful to know and understand several terms. The following terms will pop up now and then as functions in these programs:

* Synchronization, Overlapped Reads, Jitter Correction: These terms are many times used interchangeably to describe a method of reading data from an audio disc that is meant to make the extraction as accurate as possible. When reading audio, the program will reread sectors to make sure that the program is extracting audio accurately. An extreme example is presented by Andre Wiethoff in his notes about his Exact Audio Copy program: “In secure mode, this program reads every audio sector at least twice. That is one of the reasons why the program is [so] slow. But by using this technique, it could detect any nonidentical sectors. If an error occurs (read or sync error), the program keeps on reading this sector, until eight of 16 retries are identical, or a selectable number of times these 16 retries are read. So, in [the ] worst case, bad sectors are read up to 82 times! But this will help the program to find the best result by comparing all of the retries. If it is not sure that the stream is correct (at least it can be said at approximately 99.5 percent), the program will tell the user where the (possible) read error occurred.”

Overlapped and synchronized reading refers to a process of reading a certain amount of data, then going back and rereading a portion of that data and comparing it to the first read. If there is a mismatch, the data is read again from a different offset, then compared again until there is a match. This ensures that the proper data is being read even if the head positioning is not exact.

* Normalization: Different CDs are recorded at different volumes. When you make a compilation disc, there may be differences in the volume of the different songs, which can be very annoying. Normalization fixes this and sets all tracks to the same volume level.

* Track Offset: The track offset is the position of the read head in relation

to what the correct position should be. Usually the head will be a fixed offset before or after the correct read position. Once the offset is determined and adjusted for in the program, it should then position correctly on all CDs.

* Big-endian and Little-endian or Reverse Byte Order: Some audio extraction tools extract and store the files they extract in “big-endian” order, placing the “big end” at the lowest storage address used. Others store automatically in “little-endian” order, storing the “little end” byte at the lowest storage address. When tracks are extracted and stored in little-endian byte order, the files they create will sound like a bunch of static. Big-endian order stores the “big end” or most significant byte first at the lowest storage address. This approach must be reversed to be able to extract a track correctly.

* Swap Channels: Some drives swap the left and right channels when extracting audio. Some software allows you to correct this.

* CDDB: CDDB is the Compact Disc Data Base. Using CDDB, you can retrieve disc title and track names from the CDDB database on the Internet. There are several servers throughout the world that host the CDDB. CDDB can be accessed by direct TCP/IP or the HTTP protocol. Many extraction programs link to CDDB to retrieve the artist, title and song names on a disc.

* MP3, RA, VQ Encoding: Some extraction programs offer the option of encoding an extracted WAV file to MP3 or other format after the extraction is done.

BEYOND THE MENDOZA LINE: EXTRACTION SPEEDS

Extraction can be slow and unreliable or fast and reliable. It can also be fast and unreliable or slow and reliable. Let me explain. A drive that does poorly on extraction will likely run at a speed much less than its rated maximum. Other drives, accurate at extraction, can reliably rip files at almost their full rated speed. Still other drives purr along at full rated speed but produce an unacceptable output file. And, finally, when exact extraction is required, even drives like Plextor’s mighty UltraPlex will get their speed bumped down to 1X or 2X to deal with a serious synchronized read, even though that is not necessary with the latest accurate streaming technology.

Speed and reliability are dependent on the hardware and software used for the extraction task. Accurate extraction can be done at 16X and more. While there is generally no way to tell for sure whether an extraction was accurate or acceptable other than to listen to the resulting file all the way through, some programs, like Exact Audio Copy, track the extraction and report back the status of the task. If EAC reports that the file was extracted correctly, it probably was. The tradeoff for knowing that the file is good is the slow speed necessary to ensure accuracy and report on the status of the extraction.

WHO’S ZOOMIN’ WHO? THE SEARCH FOR SOUND EXTRACTION

The best approach to ensuring reliable, high-quality audio extraction is to rely on the experience of others via newsgroups and the like to know which drives do it well and which ones don’t. Fortunately for those with drive concerns, the price differentials between drives offering comparable read speeds is negligible (and doesn’t even vary that much with read speeds), so the issue is less likely to be the user’s bankroll size than simply careful selection.

And the news is even better on the software side. If you’re not satisfied with the extraction capabilities offered in the premastering software bundled with your drive (Adaptec and CeQuadrat, for example, offer solid, reliable tools that may lack some more sophisticated features available elsewhere), fear not. Many of the best tools available are Web-distributed shareware, and a representative sampling of those is corralled here. So choose wisely and rip away.

company mentioned in this article

Plextor Corporation

4255 Burton Drive, Santa Clara,

CA 95054; 800/886-3935,

408/980-1838; Fax 408/986-1010;

http://www.plextor.com; INFOLINK #417

URLs mentioned in this article

Audio Catalyst

http://www.xingtech.com

Audio Grabber

http://www.audiograbber.com-us.net/

CO Copy

http://members.aol.com/mbarth2193/

titel.htm

CDFS.VXD

http://www.maz-sound.com/cd-rippers.html

Easy CDDA Extractor

http://www.poikosoft.com/cdda/main.html

Exact Audio Copy

http://studserver.uni-dortmund.

de/~su0165/eac.html

WinDAC 32

http://www.windac.de/English/StartUp.html

MMC and SFF8020: error-free ripping?

RELATED ARTICLE: MMC and Sff8020: error-free ripping?

The ATAPI (SFF8020) specification for PC peripheral connections now includes the new MMC command set used by drive manufacturers in current CD-ROM drives. The advantage of using MMC is that many of the commands that previously needed to be performed in software can now be performed by a drive’s CD-ROM controller chip. These functions include real-time error correction of Layer 3 Reed-Solomon Product-like Code (RSPC), error detection, real-time ECC correction of one byte per P-word and Q-word, and repeated ECC passes to increase the reliability of data being read. Controllers from Oak Technology and Winbond have these functions built in.

The result of using these new chips is that now CD-ROM drives and CD-Recorders can extract data more efficiently, since less complicated algorithms are required in the ripping software. Since the controller works to position the head more accurately, existing synchronized read algorithms also work faster. Compares will now match sooner, allowing them to move on to more data quickly. This feature is called “Accurate Streaming” and drives using it can many times extract audio correctly in a fast or burst mode, which greatly increases extraction speed.

RELARED ARTICLE: driving miss DAEsy: plextor leads by example

One drive manufacturer that has demonstrably taken the lead in optimizing its drives and accompanying driver and management software for Digital Audio Extraction is Plextor Corporation. Those serious about fast, clean, reliable extraction swear by Plextor drives, and with good reason. For years, Plextor has built drives that not only push the speed and reliability envelope on data retrieval, but on Digital Audio Extraction as well. Plextor’s latest offering, the UltraPlex Wide, is a 40X max, 17X minimum CAV drive that averages 24X in Digital Audio Extraction with complete accuracy. Using an Ultra Wide SCSI connection, the drive has an 85ms average access speed, a 512KB data buffer, and data transfer rates of up to 40MB/sec in burst transfer mode. The drive has front panel controls for playing audio CDs and the firmware can be flashed as BIOS improvements become available. The drive uses SCAM (SCSI Configured Auto Magically) technology to set SCSI IDs and termination automatically.

The UltraPlex Wide ships with Plextor Manager software, currently in version 1.73. This utility pops up with four tabs–Drive control, Disc Info, Audio Control, and A/V Player. The Drive Control lists the host adapter number, the SCSI ID, the firmware revision, and the buffer size of the selected drive. It allows you to change the drive speed, set the spin-down time, enable/disable Plextor’s AudioFS conversion tool, and lock and unlock the drive tray. Disc Info shows you the type of disc, number of tracks, number of sessions, and the disc label. From there, you can call DiscDupe, the Plextor disc copy utility, assuming that you have a Plextor recorder. Audio Control lets you set the volume and balance for audio discs, switch the left and right channels, and reset the drive. The A/V Player will play audio, WAV files, AVI files, and MPEG files.

Two other features of the Plextor Manager are notable. The Audio Capture feature is simple and fast. The Audio capture screen lets you choose the track number to extract, the sampling rata, and the channel setup. Choosing Capture lets you choose the destination directory and begin the extraction. This program is simple and easy to use, but the best thing about it is the speed. Extracting a four-minute, 30-second track took 13 seconds! That is a 24X extraction, as advertised, and the file was perfectly clean. You can see why people swear by Plextor drives for Digital Audio Extraction.

The other feature is AudioFS, which makes .cda (Compact Disc Audio) tracks on a CD look like WAV files. This feature is especially useful if you are compressing to MP3. Instead of having to extract WAVs to the hard drive–using up 40 to 50MB of disk space per file–you can use the simulated WAV on the CD audio disc as a source and compress it directly to MP3. And since the files look like WAVs to Windows, you can play them through the SCSI bus, without a physical cable connection to your sound card. This is a very handy feature for external SCSI drives. (For those of you who don’t have a Plextor drive and thus no access to this conversion tool, try the alternate CDFS.VXD mentioned in the sidebar “Breaking the WAVs: CDFS.VXD.” It does not work with all drives, but if it works with yours, you can have this handy feature, too.)

For companies using audio extraction as an integral part of a custom audio disc production system, Plextor has combined these elements and more in a turnkey solution. Incorporating automated extraction and recording software in an integrated network, the key selling point of the system remains the extraction-optimized Plextor drives found in the MegaPlex towers from which the stored audio tracks are drawn after the customer selects them. The system provides a sound model for how digital audio extraction can play a key role in aggressive new technology-based business models.

RELATED ARTICLE: breaking the WAVs: CDFS.VXD

If your plans are to create MP3 files or other compressed audio formats, creating a WAV file on hard disk first, and then compressing it into the secondary format, is a waste of time and disk space. There is a handy solution that bypasses the creation of a WAV altogether. CDFS.VXD is a freeware device driver that replaces the Microsoft CDFS.VXD (Compact Disc File System) in the subdirectory c:windowssystemiosubsys.

Once the driver is installed, Compact Disc Audio files (.cda), appear as WAVs and can be opened directly from the CD in a wave editor and otherwise treated as WAV files. Opening the file in a WAV editor and then saving it to hard disk gives you the same result as extracting the track from the disc. You can also use any WAV-to-MP3 converter to convert the cda file directly from the audio CD to MP3 (or other compressed format) without having first to extract it to hard disk. This driver will work with some drives, but not others.

When you open a CD after this replacement driver is installed, you will see two subdirectories on the disc in addition to the audio tracks. These subdirectories are Mono and Stereo. Under each subdirectory, you will see three additional subdirectories: 11.025KHz, 22.050KHz, and 44.100KHz. Opening these directories reveals the WAV files with the usual Windows WAV icons. Right click on one of the WAVs and choose Properties. If the file properties box shows the preview tab, then the drive is supported by this driver, if only the general tab is showing, then the drive is not capable of working with the new driver.

You can get the driver from http://www.maz-sound. com/cd-rippers.html. To install the driver, go to the windows systemiosubsys directory and rename CDFS.VXD to something else. Then unzip the file and copy the new cdfs.vxd into the directory.

Robert A. Starrett (bobs@cdpage.com) is a contributing editor for EMedia Professional, co-columnist for THE CD WRITER, and an independent consultant based in Denver, Colorado. He is the co-author of CD-ROM Professional’s CD-Recordable Handbook.

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