llbbl
09-08-2002, 10:07 PM
The battle for high end digital recordings has been taking place for several years now. It has been compared to that of the battle between Betamax and VHS. We all know how stubborn Sony can be about their standards, so it is unlikely that SACD will be leaving the market any time soon. DVD-A is the other side of the equation and appears to have the advantage at this point. This is because of the likelyhood that the new DVD players will support DVD-A.
To understand how the new formats differ from CD technology you must start with how the "raw" audio is sampled. DVD-A using a technology called Pulse Code Modulation (PCM). Here is a good article on optimizing PCM for (http://cips02.physik.uni-bonn.de/~scheller/audio/main.html) different audio formats. If you listen to mp3's than you may have a good understanding of what makes music sound better. DVD-A increases the sampling rate from 44,100 kHz to a max of 192 kHz. It is true that the human ear can not differenate between sounds above 64 kHz and this is why the normal sampling rate of DVD-A is 96 kHz. Sony and Phillips have developed Direct Stream Digital (DSD) to compete against PCM. Here is a more (http://www.dcsltd.co.uk/papers/effects.pdf)(.pdf) indepth paper that describes the differences between the two. The sampling rate of DSD is 2.82 MHz. I know you are thinking that this is way over kill, if our level of hearing is from 20 Hz to 20 kHz (http://www.sfu.ca/sca/Manuals/ZAAPf/r/range.html), and didn't I just say that 64 kHz was the limit. Well with the higher sampling rates their is some audio qualities to the sound that can be distinguished, not the frequency discrimination limit of the human ear based on two pure tones. That is another key factor, music is many times not a pure tone but a mixture / combination of a multitude of tones.
It gets even more confusing when the audiophiles start talking about noise floor, dynamic range, word length and how these affect a digital recording system. I gathered word length to equal the number of bits that music is recorded at. CD's are recorded in 16-bit, DVD-Video in 20-bit (generally), DVD-A up to 24-bit and SACD recorded in 1-bit. I don't understand the explanation fully that I found on why SACD uses a goofy bit length, but here is what I found on ABCnews.com (http://abcnews.go.com/sections/tech/CuttingEdge/cuttingedge001013.html) Now I am trying to figure out how the different bit rates that you can record mp3's are similar to the word length. I think they are talking about two different technologies because you have to remember that mp3 is lossy and these new formats are lossless. The mp3 kbit is the rate of sampling that is done when the song is converted from its supposed lossless form on the CD.
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References
http://www.surroundpro.com/2001/11_12/feature_horror.shtml
http://whatis.techtarget.com/definition/0,,sid9_gci214387,00.html
http://www.audiorevolution.com/equip/dvdavssacd/
http://www.dolby.com/digital/
http://www.ambisonic.net/mlp.html
http://www.sel.sony.com/SEL/consumer/dsd/dsd.pdf
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I'm not done yet, but it's time for bed. I will finish it later, I promise!
To understand how the new formats differ from CD technology you must start with how the "raw" audio is sampled. DVD-A using a technology called Pulse Code Modulation (PCM). Here is a good article on optimizing PCM for (http://cips02.physik.uni-bonn.de/~scheller/audio/main.html) different audio formats. If you listen to mp3's than you may have a good understanding of what makes music sound better. DVD-A increases the sampling rate from 44,100 kHz to a max of 192 kHz. It is true that the human ear can not differenate between sounds above 64 kHz and this is why the normal sampling rate of DVD-A is 96 kHz. Sony and Phillips have developed Direct Stream Digital (DSD) to compete against PCM. Here is a more (http://www.dcsltd.co.uk/papers/effects.pdf)(.pdf) indepth paper that describes the differences between the two. The sampling rate of DSD is 2.82 MHz. I know you are thinking that this is way over kill, if our level of hearing is from 20 Hz to 20 kHz (http://www.sfu.ca/sca/Manuals/ZAAPf/r/range.html), and didn't I just say that 64 kHz was the limit. Well with the higher sampling rates their is some audio qualities to the sound that can be distinguished, not the frequency discrimination limit of the human ear based on two pure tones. That is another key factor, music is many times not a pure tone but a mixture / combination of a multitude of tones.
It gets even more confusing when the audiophiles start talking about noise floor, dynamic range, word length and how these affect a digital recording system. I gathered word length to equal the number of bits that music is recorded at. CD's are recorded in 16-bit, DVD-Video in 20-bit (generally), DVD-A up to 24-bit and SACD recorded in 1-bit. I don't understand the explanation fully that I found on why SACD uses a goofy bit length, but here is what I found on ABCnews.com (http://abcnews.go.com/sections/tech/CuttingEdge/cuttingedge001013.html) Now I am trying to figure out how the different bit rates that you can record mp3's are similar to the word length. I think they are talking about two different technologies because you have to remember that mp3 is lossy and these new formats are lossless. The mp3 kbit is the rate of sampling that is done when the song is converted from its supposed lossless form on the CD.
----
References
http://www.surroundpro.com/2001/11_12/feature_horror.shtml
http://whatis.techtarget.com/definition/0,,sid9_gci214387,00.html
http://www.audiorevolution.com/equip/dvdavssacd/
http://www.dolby.com/digital/
http://www.ambisonic.net/mlp.html
http://www.sel.sony.com/SEL/consumer/dsd/dsd.pdf
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I'm not done yet, but it's time for bed. I will finish it later, I promise!