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Old 14th November 2002, 05:47 AM   #1
jteef is offline jteef  United States
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Default Copy Protected CD's and DRM

I dont know much about the intracacies of CD Players and how they work, but I was planning on building a DAC to learn more about it at some point.

Does all the talk of copy protected CD's and all this Digital Rights Management stuff, if implemented, threaten the functionality of DIY DAC's and transports?

I would hate to drop some coin on a DAC and learn that it wont work with cd's manufactured a year from now.

Thanks

jt
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Old 14th November 2002, 06:36 AM   #2
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Default Re: Copy Protected CD's and DRM

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Originally posted by jteef
copy protected CD's
1st off copy protected disks are not CDs. They do not comply with the redbook standard and can't be called CDs (and if you look closely they don't have the logo on them).

[political statement] If you end up with one of these, take it back, demand your money back, let them rot on the shelves and in the wharehouses[/political statement]

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Old 14th November 2002, 08:40 AM   #3
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The music companies are trying to say that copy protected cd's are red book compliant.

You may find this link of interest:

http://www.theregister.co.uk/content/54/27960.html



Jim.
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Old 14th November 2002, 09:23 AM   #4
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Default Re: Copy Protected CD's and DRM

Quote:
Originally posted by jteef
I dont know much about the intracacies of CD Players and how they work, but I was planning on building a DAC to learn more about it at some point.

Does all the talk of copy protected CD's and all this Digital Rights Management stuff, if implemented, threaten the functionality of DIY DAC's and transports?

I would hate to drop some coin on a DAC and learn that it wont work with cd's manufactured a year from now.
The CD-drive is (may be) affected by the copy protection. Some drives refuses to play some CD's but a DAC is never affected. The signal out from a CD-player is always SPDIF and the DAC doesn't pay attention to the "copy inhibit" flag inside the SPDIF signal. This signal has always been there but nobody has noticed that.
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Old 14th November 2002, 12:08 PM   #5
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I don't think there is a lot of copy protected 1st off discks out there. I have some idea because I copy a lot. All the copies are protected, but I didn't experience much trouble on most transports. A DAC doesn't care at all what is being delivered from a transport (unless we are talking about SACD format).
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Old 14th November 2002, 12:42 PM   #6
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I think they are coming in slowly. In Sweden lately there have been vivid discussions after BMG apparently decided to protect ALL their CDs. One example in your part of the world (and the rest) seems to be the new Celine Dion album which apparently does not play very well in computers.

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Old 21st November 2002, 01:24 PM   #7
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I don't understand why they try to make those copy protected CDs. Even before the copy protected Celine Dion was for sale, you could get a copy on the Internet from any place, IRC, ftp, http, news channel, file sharing systems and so on. I know because I saw it myself. Why do anyone bother to copy the CD, when you can download it from the Internet? (I didn't say I did it myself )
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Old 21st November 2002, 01:29 PM   #8
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And by the way, everybody with a stand alone CD-player with digital output (optical or coaxial) and a computer with a soundcard with digital input can get a perfect digital copy of a copy protected CD (there are a lot of cheap soundcards that copies 1 to 1 on the digital input, for instance Hoontech and Terratec cards. NOTE! NOT Soundblaster Cards!!!). The copy protection has no affect on the S/PDIF stream, so do not worry for your DAC.
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Old 21st November 2002, 01:30 PM   #9
UrSv is offline UrSv  Sweden
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Possibly people copy CDs because that takes 2 minutes for a near identical copy and downloading via modem takes hours and all you get is MP3 at 128k normally. Full quality or MP3 - the choice is easy and/or yours. Or is the Internet full of people who share full quality rips (which mean then you need to download some 500-700 MB for CD)? I don't know about it if that is the way things work for people who download music. I never do. I have two copied CDs and they are my own for car use.

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Old 21st November 2002, 11:43 PM   #10
hifiZen is offline hifiZen  Canada
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Actually, the copy protection mechanisms being used now go way beyond setting the "copy inhibit" bit in the Q-channel subcode. This copy protect bit was included in the original red book standard, and is also carried in SPDIF digital link, but as has been said, it is often ignored by equipment. It is also very easy to strip this bit, as there's no encryption or other tamper resistant system to protect it.

Current CD anti-copy techniques don't meet the red book standard because they do some truly vile things in order to mess up computer drives trying to read the discs. One technique I've read about involves deliberately corrupting the CRC codes and the accompanying data on the original disc so that there are lots of C2 errors which occur during playback. A C2 error normally happens only when there is so much data loss during playback, that the error codes can't be used to restore the original data values (disc read errors which can be corrected by the Reed-Solomon codes are termed C1 errors, and there is no data loss during a C1 event). When an audio CD player encounters a C2 error, it usually ignores the sample value (since it's corrupt data), and instead takes a guess at what the sampe value was supposed to be by interpolating the waveform, or using other techniques. This is called error concealment, and generally renders most C2 errors inaudible. Long sequences of C2 errors, however, are what become audio drop-outs and the other nasties you hear when playing a badly damaged or very dirty disc.

However, when a CD-ROM drive plays a disc, it has no idea what it's playing. CD media is CD media. So a CD-ROM drive will not attempt any kind of audio error concealment when it detects C2 errors. Instead, it may conclude that the CRC values themselves are totally invalid (which they are), and will pass the bad data along anyway. When you then burn a copy, the bad sample values get written to disc as valid data, along with all the normal samples, and everything gets a correct CRC code. Now that bad data looks legit to any CD device which reads that disc, so no error concealment will take place. The result is periodic bursts of noise, or clicks interspersed throughout the music... the intention is to make the music unlistenable or at least less enjoyable.

There are other techniques, such as modifying TOC or other areas on the disc to confuse CD-ROM drives, but not typical audio-only players. These are arguably even worse than the bad CRC trick. Why should I not be allowed to listen to a disc I paid for, on whatever playback device I own. What if I only had a computer for playing CDs?


This is a repugnant practice, not only because it violates the red book standard, but because it often also reduces the fidelity of the music by relying on C2 error concealment to hide all the bad data. Furthermore, when there are *real* C2 errors, your player will have less ability to correct them due to the reduction in valid data available to help with the error concealment. It's equivalent to buying a second-hand disc which is badly scratched... except the scratches are invisible to the human eye, and 99% of consumers who don't understand the technical details. You're paying full price for it , and the record label is screwing you deliberately!

This practice should be roundly condemned! It is unethical to sell consumers a deliberately defective product, under the pretence that it is a red-book compliant CD (and no, not all of these copy protected discs have removed the CD logo, nor do they all have labelling indicating that they may not work properly in some playback devices). These businesses are shooting themselves in the foot by deceiving and ripping off their own customers. Problem is, they're digging deeper and deeper holes for themselves as the animosity between RIAA/record labels and the public grows. Will they ever learn?

I agree with Planet10 - be on the lookout for these discs, and whatever you do, DON'T BUY THEM!
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