This chapter is from the book
This chapter is from the book
This chapter is from the book
Ripping/Copying Discs
All optical drives can play Red Book–formatted CD-DA discs, but not all optical drives can read CD-DA discs. The difference sounds subtle, but it is actually quite dramatic. If you enjoy music and want to use your PC to manage your music collection, the ability to read the audio data digitally is an important function for your CD (and DVD) drives because it enables you to much more easily and accurately store, manipulate, and eventually write back out audio tracks.
To record a song from CD to your hard disk, it was once necessary to play the disc at normal speed and capture the audio output as analog, hence the need for the four-wire analog audio cable connection from the rear of optical drives to your sound card. Fortunately, for several years drives have supported digital audio extraction (DAE). In this process, they read the digital audio sectors directly and, rather than decode them into analog signals, pass each 2,352-byte sector of raw (error-corrected) digital audio data directly to the PC's processor via the drive interface cable (ATA, SATA, SCSI, USB, or FireWire). Therefore, no digital-to-analog conversion (and back) occurs, and you essentially get the audio data exactly as it was originally recorded on the CD (within the limits of the CD-DA error-correction standards). You would have essentially extracted the exact digital audio data from the disc onto your PC.
Another term for digital audio extraction is ripping, so named because you can "rip" the raw audio data from the drive at full drive read speed, rather than the normal 1x speed at which you listen to audio discs. Actually, most drives can't perform DAE at their full rated speeds. Although some are faster (or slower) than others, most perform DAE at speeds from about one-half to two-thirds of their rated CD read speed. So, you might be able to extract audio data at speeds only up to 28x on a 40x rated drive. However, that is still quite a bit better than at 1x as it would be on drives that can't do DAE (not to mention skipping the conversion to analog and back to digital with the resultant loss of information).
Virtually all newer optical drives can perform digital audio extraction on music discs. How fast or accurately they do this varies from model to model. You might think any extraction (digital copy) of a given track (song) should be the same because it is a digital copy of the original; however, that is not always the case. The CD-DA format was designed to play music, not to transfer data with 100% accuracy. Errors beyond the capability of the CIRC in the CD-DA format cause the firmware in the drive to interpolate or approximate the data. In addition, time-based problems due to clock inaccuracies can occur in the drive, causing it to get slightly out of step when reading the frames in the sector (this is referred to as jitter). Differences in the internal software (firmware) in the drive and differences in the drivers used are other problems that can occur.
"For Music Use Only" CD-R/RW Discs
According to the Audio Home Recording Act of 1992, consumer CD recordable drives and media sold specifically for recording music are required to have specific safeguards against copying discs, mainly SCMS. That means these recorders can make digital copies only from original prerecorded discs. You can copy a copy, but in that case, the data being recorded goes from digital to analog and back to digital on the second copy, resulting in a generational loss of quality.
The media for these recorders must be special as well. They work only with special discs labeled "For Music Use," "For Audio," or "For Consumer." These carry the standard Compact Disk Digital Audio Recordable logo that most are familiar with, but below that, as part of the logo, is an added line that says "For Consumer." These discs feature a special track prerecorded onto the disc, which the consumer music recorders look for. Built into the price of the AHRA-compliant media is a royalty for the music industry that this track protects. The media costs about 20%–30% more than what regular CD-R/RW media costs. If you try to use standard non-AHRA-compliant CD-R/RW discs in these drives, the drive refuses to recognize the disc. These music devices also refuse to copy data discs.
Note that this does not apply to the optical drive you have installed or attached to your PC. It does not have to be AHRA compliant, nor does it need to use AHRA-compliant "For Music Use" media, even if you are copying or recording music discs. Additionally, you can make digital copies of copies—the SCMS does not apply, either. The bottom line is that you do not have to purchase AHRA-compliant discs for the optical drives in your PC. If you do purchase such discs, despite the "For Music Use Only" designation, AHRA-compliant discs can be used in your optical drives just as regular CD-R/RW discs can be used for storing data. The extra information indicating AHRA compliance is simply ignored.
CD Copy Protection
Worries about the public copying of software and music CDs has prompted the development of copy protection techniques that attempt to make these discs uncopyable. There are different methods of protecting software CDs versus music CDs, but the end result is the same: You are prevented from making normal copies, or the copies don't work properly. In the case of music CDs, the copy protection can be quite obtrusive, adding noise to the recording, and in extreme cases preventing the disc from even playing in a PC drive.
Several copy protection schemes are available for CD-DA (digital audio) discs, ranging from the simple to sophisticated. The most popular protection scheme for digital audio discs is called SafeAudio by Macrovision. Macrovision won't explain exactly how SafeAudio works, but it purchased the technology from a company called TTR Technologies and patents filed by TTR describe the scheme in detail. According to the patents, the disc is deliberately recorded with grossly erroneous values (bursts of noise) in both the audio data and the codes, which would typically be used to correct these errors. When the disc is read, the normal error-correction scheme fails, leaving small gaps in the music. When this happens on a standard audio CD player, the gaps are automatically bridged by circuitry or code in the player, which looks at the audio data on either side of the gap and interpolates (guesses) the missing values. The CD drive in a PC can do the same thing, so the interpolation occurs only when playing CDs in an audio player mode. However, the drive in a PC does not perform this same interpolation when "ripping" the data—that is, copying it directly to a hard drive, another CD, or some other medium. In that case, the unbridged gaps are heard as extremely loud clicks, pops, and noise. Both TTR and Macrovision claim that the interpolation that occurs when playing a SafeAudio disc is not discernable to the human ear, but many audio experts disagree. To an audiophile, the addition of any distortion or noise to the audio signal is unconscionable, plus you can't make legal backups of your music—something that is allowed by law. Because of these problems, I recommend avoiding the purchase of audio CDs containing SafeAudio or any other form of copy protection.
CD Digital Rights Management
Digital rights management (DRM) goes a step beyond standard copy protection by specifying what you can and cannot do with a recorded CD or other type of commercial media. When applied to downloaded music, for example, DRM features in audio tracks can prevent you from burning a song to CD an unlimited amount of times, playing a song past a particular date, or limit the number of times you can copy a song from one PC to another.
Although the use of DRM on CD media (as opposed to downloadable audio tracks) has been rare, the Sony rootkit scandal of 2005 is a useful case to keep in mind.
Sony BMG, one of the biggest music CD distributors, introduced a controversial method of copy protection and DRM in the fall of 2005 by adding copy protection and DRM to some of its music CDs. Affected CDs used either XCP (Extended Copy Protection, developed by First 4 Internet, now known as Fortium Technologies, Inc.) or MediaMax CD-3 (developed by SunnComm).
These programs limited the user's ability to work freely with the songs (as can be done with normal music CDs), and, worse yet, were installed on PCs without the user being notified. The type of installer Sony used is called a rootkit, which is a program that hides its presence from the OS and makes it easier for worms and other malware to attack the system.
After security and privacy advocates attacked Sony's use of DRM and rootkits without adequate notice to music purchasers, Sony introduced a rootkit removal tool and eventually recalled all albums in 2006, settling a lawsuit with the Federal Trade Commission. Although Sony's attempt to use DRM was botched by its failure to inform customers that CDs contained DRM software and the software did not provide a way for users to block installation, it's possible that DRM features that avoid Sony's mistakes may be used on CD and other types of media in the future.
DVD Copy Protection
DVD-Video discs employ several levels of protection that are mainly controlled by the DVD Copy Control Association (DVD CCA) and a third-party company called Macrovision (they developed SafeDisk).
This protection typically applies only to DVD-Video discs, not DVD-ROM software. So, for example, copy protection might affect your ability to make backup copies of The Matrix, but it won't affect a DVD encyclopedia or other software application distributed on DVD-ROM discs.
Note that every one of these protection systems has been broken, so with a little extra expense or the correct software, you can defeat the protection and make copies of your DVDs either to other digital media (hard drive, optical drive, flash drive, and so on) or to analog media (such as a VHS or other tape format).
A lot of time and money are wasted on these protection schemes, which can't really foil the professional bootleggers willing to spend the time and money to work around them. But they can make it difficult for the average person to legitimately back up his expensive media.
The four main protection systems used with DVD-Video discs are as follows:
- Regional Playback Control (RPC)
- Content Scrambling System (CSS)
- Analog Protection System (APS)
- ProtectDisc
RPC
Regional playback was designed to allow discs sold in specific geographical regions of the world to play only on players sold in those same regions. The idea was to allow a movie to be released at different times in different parts of the world and to prevent people from ordering discs from regions in which the movie had not been released yet.
Eight regions are defined in the RPC standard. Discs (and players) usually are identified by a small logo or label showing the region number superimposed on a world globe. Multiregion discs are possible, as are discs that are not region locked. If a disc plays in more than one region, it has more than one number on the globe. The regions are as follows:
- Region Code 1—United States, Canada, U.S. Territories, Bermuda.
- Region Code 2—Japan, Western Europe, South Africa, and the Middle East.
- Region Code 3—Southeast Asia and East Asia.
- Region Code 4—Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, and the Caribbean.
- Region Code 5—Eastern Europe (east of Poland and the Balkans), Indian subcontinent, Africa, North Korea, and Mongolia.
- Region Code 6—China and Tibet.
- Region Code 7—Reserved for future use.
- Region Code 8—International venues including aircraft and cruise ships.
- Region Code All—Has all flags set, allowing the disc to be played in any region or player. Sometimes called Region Code 0.
The region code is embedded in the hardware of DVD video players. Most players are preset for a specific region and can't be changed. Some companies who sell the players modify them to play discs from all regions; these are called region-free or code-free players. Some newer discs have an added region code enhancement (RCE) function that checks to see whether the player is configured for multiple or all regions and then, if it is, refuses to play. Most newer region-free modified players know how to query the disc first to circumvent this check as well.
DVD-ROM drives used in PCs originally did not have RPC in the hardware, placing that responsibility instead on the software used to play DVD video discs on the PC. The player software would usually lock the region code to the first disc that was played and then from that point on, play only discs from that region. Reinstalling the software enabled the region code to be reset, and numerous patches were posted on websites to enable resetting the region code even without reinstalling the software. Because of the relative ease of defeating the region-coding restrictions with DVD-ROM drives, starting on January 1, 2000, all DVD-ROM and rewritable DVD drives were required to have RPC-II, which embeds the region coding directly into the drive.
RPC-II (or RPC-2) places the region lock in the drive, and not in the playing or MPEG-2 decoding software. You can set the region code in RPC-II drives up to five times total, which basically means you can change it up to four times after the initial setting. Usually, the change can be made via the player software you are using, or you can download region-change software from the drive manufacturer. Upon making the fourth change (which is the fifth setting), the drive is locked on the last region set.
Region Codes Used by BD
A different region code scheme that divides the world into three regions is used by BD:
- Region A includes North America, Central America, South America, Korea, Japan, and South East Asia.
- Region B includes Europe, the Middle East, Africa, Australia, and New Zealand.
- Region C includes Russia, India, China, and the rest of the world.
A BD without a region code can be played by players with any region code.
CSS
The CSS provides the main protection for DVD-Video discs. It wasn't until this protection was implemented that the Motion Picture Association of America (MPAA) agreed to release movies in the DVD format, which is the main reason the rollout of DVD had been significantly delayed.
CSS originally was developed by Matsushita (Panasonic) and is used to digitally scramble and encrypt the audio and video data on a DVD-Video disc. Descrambling requires a pair of 40-bit (5-byte) keys (numeric codes). One of the keys is unique to the disc, whereas the other is unique to the video title set (VTS file) being descrambled. The disc and title keys are stored in the lead-in area of the disc in an encrypted form. The CSS scrambling and key writing are carried out during the glass mastering procedure, which is part of the disc manufacturing process.
You can see this encryption in action if you put a DVD disc into a DVD-ROM drive on a PC, copy the files to your hard drive, and then try to view the files. The files are usually called VTS_xx_yy.VOB (video object), where xx represents the title number and yy represents the section number. Typically, all the files for a given movie have the same title number and the movie is spread out among several 1GB or smaller files with different section numbers. These VOB files contain both the encrypted video and audio streams for the movie interleaved together. Other files with an IFO extension contain information used by the DVD player to decode the video and audio streams in the VOB files. If you copy the VOB and IFO files onto your hard drive and try to click or play the VOB files directly, you either see and hear scrambled video and audio or receive an error message about playing copy-protected files.
This encryption is not a problem if you use a CSS-licensed player (either hardware or software) and play the files directly from the DVD disc. All DVD players, whether they are consumer standalone units or software players on your PC, have their own unique CSS unlock key assigned to them. Every DVD video disc has 400 of these 5-byte keys stamped onto the disc in the lead-in area (which is not usually accessible by programs) on the DVD in encrypted form. The decryption routine in the player uses its unique code to retrieve and unencrypt the disc key, which is then used to retrieve and unencrypt the title keys. CSS is essentially a three-level encryption that originally was thought to be very secure but has proven otherwise.
In October 1999, a 16-year-old Norwegian programmer was able to extract the first key from one of the commercial PC-based players, which allowed him to very easily decrypt disc and title keys. A now famous program called DeCSS was then written that can break the CSS protection on any DVD video title and save unencrypted VOB files to a hard disk that can be played by any MPEG-2 decoder program. Needless to say, this utility (and others based on it) has been the cause of much concern in the movie industry and has caused many legal battles over the distribution and even links to this code on the Web. Do a search on DeCSS for some interesting legal reading.
As if that weren't enough, in March 2001, two MIT students published an incredibly short (only seven lines long!) and simple program that can unscramble CSS so quickly that a movie can essentially be unscrambled in real time while it is playing. They wrote and demonstrated the code as part of a two-day seminar they conducted on the controversial Digital Millennium Copyright Act, illustrating how trivial the CSS protection really is.
ProtectDisc
The newest DVD copy protection system is called ProtectDisc. Its DVD-Video version changes the standard structure of the disc to prevent copying. Unfortunately, a DVD movie created using ProtectDisc cannot be viewed with PC-based player programs such as WMP or WinDVD.
Cinavia
Ciniavia (http://www.cinavia.com/languages/english/index.html) is the company responsible for copy-protection for BD movies. If you attempt to create a copy of a BD disc, Cinavia displays messages such as "Copying Stopped. The content being copied is protected by Cinavia and is not authorized for copying from this device." Similar messages are displayed when attempting to play back an unauthorized copy. Cinavia can also mute audio from unauthorized copies.
Is Copy Protection "Unbreakable?"
Despite the claims of "unbreakable" copy protection, ProtectDisc's method, like the others discussed here, was quickly overcome. Similarly, enterprising users have figured out how to bypass Cinavia's copy protection methods (which apply only to BD set-top boxes, not to BD drives in PCs). As with other copy-protection schemes, legitimate users who don't try to "beat the system" often wind up being victimized—in the case of ProtectDisk, by being unable to use a PC to watch the movie.