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#1
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Raw laser readout from compact disc?
Hi all,
I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands |
#2
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Raw laser readout from compact disc?
Get a good microscope. All you see it pits, that's all the Laser sees.
A pit disperses the laser light so in that bit time there is no signal and no pit reflects the light there is a signal. The signal in question is a 1 or a 0. "Sidney Cadot" wrote in message ... Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands |
#3
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Raw laser readout from compact disc?
Get a good microscope. All you see it pits, that's all the Laser sees.
A pit disperses the laser light so in that bit time there is no signal and no pit reflects the light there is a signal. The signal in question is a 1 or a 0. "Sidney Cadot" wrote in message ... Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands |
#4
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Raw laser readout from compact disc?
Get a good microscope. All you see it pits, that's all the Laser sees.
A pit disperses the laser light so in that bit time there is no signal and no pit reflects the light there is a signal. The signal in question is a 1 or a 0. "Sidney Cadot" wrote in message ... Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands |
#5
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Raw laser readout from compact disc?
Richard Tomkins wrote:
Get a good microscope. All you see it pits, that's all the Laser sees. Are they really visible using an optical microscope? Given that the pit depth is the quarter of the wavelength of the laser (780 nm) I would find it surprising if these could be seen using anything other than an electron microscope. A pit disperses the laser light so in that bit time there is no signal and no pit reflects the light there is a signal. As I understand it, the psysical effect that attenuates the reflected signal is not dispersion but rather destructive interference (given the pit depth of 1/4*lambda, the extra pathlength is 1/2*lambda, so this interferes destructively). The signal in question is a 1 or a 0. The transition land/pit and pit/land denote ones, no transition denotes zeros. All this is then fed into the EFM decoder. Unfortunately, all this doesn't really help to find what I'm looking for: some real-life data recorded directly from the laser sensor. My problem isn't so much that I need a feel for the physical layout (interesting as that may be); I would like to verify my understanding of the algorithms, which are largely mathematical in nature. There is some funky mathematics going on in the error correction - I like to think I understand it, but it would be nice to check. For that I really need at least a couple of thousands samples of raw information from the laser as it follows the track (preferably still analog). Best regards, Sidney |
#6
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Raw laser readout from compact disc?
Richard Tomkins wrote:
Get a good microscope. All you see it pits, that's all the Laser sees. Are they really visible using an optical microscope? Given that the pit depth is the quarter of the wavelength of the laser (780 nm) I would find it surprising if these could be seen using anything other than an electron microscope. A pit disperses the laser light so in that bit time there is no signal and no pit reflects the light there is a signal. As I understand it, the psysical effect that attenuates the reflected signal is not dispersion but rather destructive interference (given the pit depth of 1/4*lambda, the extra pathlength is 1/2*lambda, so this interferes destructively). The signal in question is a 1 or a 0. The transition land/pit and pit/land denote ones, no transition denotes zeros. All this is then fed into the EFM decoder. Unfortunately, all this doesn't really help to find what I'm looking for: some real-life data recorded directly from the laser sensor. My problem isn't so much that I need a feel for the physical layout (interesting as that may be); I would like to verify my understanding of the algorithms, which are largely mathematical in nature. There is some funky mathematics going on in the error correction - I like to think I understand it, but it would be nice to check. For that I really need at least a couple of thousands samples of raw information from the laser as it follows the track (preferably still analog). Best regards, Sidney |
#7
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Raw laser readout from compact disc?
Richard Tomkins wrote:
Get a good microscope. All you see it pits, that's all the Laser sees. Are they really visible using an optical microscope? Given that the pit depth is the quarter of the wavelength of the laser (780 nm) I would find it surprising if these could be seen using anything other than an electron microscope. A pit disperses the laser light so in that bit time there is no signal and no pit reflects the light there is a signal. As I understand it, the psysical effect that attenuates the reflected signal is not dispersion but rather destructive interference (given the pit depth of 1/4*lambda, the extra pathlength is 1/2*lambda, so this interferes destructively). The signal in question is a 1 or a 0. The transition land/pit and pit/land denote ones, no transition denotes zeros. All this is then fed into the EFM decoder. Unfortunately, all this doesn't really help to find what I'm looking for: some real-life data recorded directly from the laser sensor. My problem isn't so much that I need a feel for the physical layout (interesting as that may be); I would like to verify my understanding of the algorithms, which are largely mathematical in nature. There is some funky mathematics going on in the error correction - I like to think I understand it, but it would be nice to check. For that I really need at least a couple of thousands samples of raw information from the laser as it follows the track (preferably still analog). Best regards, Sidney |
#8
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Raw laser readout from compact disc?
Sidney Cadot wrote:
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) The raw data stream has historically been a readily-probable test point in each CD player. You just need to attach some kind of high speed data recorder to it. |
#9
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Raw laser readout from compact disc?
Sidney Cadot wrote:
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) The raw data stream has historically been a readily-probable test point in each CD player. You just need to attach some kind of high speed data recorder to it. |
#10
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Raw laser readout from compact disc?
Sidney Cadot wrote:
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) The raw data stream has historically been a readily-probable test point in each CD player. You just need to attach some kind of high speed data recorder to it. |
#11
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Raw laser readout from compact disc?
Sidney Cadot wrote in message ...
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands This link shows you the signal from the laser known as the "eye pattern" jeff |
#12
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Raw laser readout from compact disc?
Sidney Cadot wrote in message ...
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands This link shows you the signal from the laser known as the "eye pattern" jeff |
#13
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Raw laser readout from compact disc?
Sidney Cadot wrote in message ...
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands This link shows you the signal from the laser known as the "eye pattern" jeff |
#14
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Raw laser readout from compact disc?
Sidney Cadot wrote in message ...
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands forgot the link http://www.sony.net/SonyInfo/News/Press/200405/04-026E/ |
#15
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Raw laser readout from compact disc?
Sidney Cadot wrote in message ...
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands forgot the link http://www.sony.net/SonyInfo/News/Press/200405/04-026E/ |
#16
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Raw laser readout from compact disc?
Sidney Cadot wrote in message ...
Hi all, I am trying to gain an in-depth understanding of the digital encoding used in compact discs, out of hobby interests. I think I got a grasp of all the algorithms involved (CIRC encoding, EFM, and so on) but I would like to verify my understanding by looking at the actual raw (analog) signal as seen by the laser sensor in the CD's optical system. For this purpose, it would be quite ideal to have access to a couple of seconds worth of audio data as seen by the laser reflection pickup sensor; something like 20 Msamples/sec at 8 bits/sample would be perfect for me. Would anybody know how I could get hold of this kind of data? I assume that it is routinely produced by producers of CD hardware, but they will probably not be keen to share :-) Any pointers would be greatly appreciated. Best regards, Sidney Cadot The Netherlands forgot the link http://www.sony.net/SonyInfo/News/Press/200405/04-026E/ |
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