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Data Integrity Question

Last response: in Storage
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February 11, 2011 6:03:17 PM

Hello Everyone,

Like millions of others I'm looking at archiving my music library from cd. I have decided to use apple lossless format. I currently only have one computer, but plan on building a home server as soon as its economically feasible. I want to begin scanning in my music now.

My question is this: If I scan my music in on my current rig and then transfer it later via wi-fi network (or hardwired?) connection to a new rig will there by any integrity/quality loss? If there is any chance of a large transfer degrading quality I will wait until I built my home server before I begin scanning. Thank you in advance.
a c 342 G Storage
February 11, 2011 7:15:50 PM

Almost no chance. The huge advantage of digital data storage over analogue is that a copy of a digital file is EXACTLY the same as the original (unless there is data corruption, which is rare and usually detected immediately). Unlike analogue copying, a copy of a copy of a copy of a copy ... in the digital world is still the same as the original. That is, as long as the file writing is done in a lossless manner.

You say you are using a lossless format for the original file. Once that is done, a copy of that file is identical to the original. Where confusion can arise is with software that does allow minor detail loss, and is used repeatedly. For example, some software to write photos in .jpg format allows for lossy storage to decrease file size. Merely copying such a file does not change the contents. BUT if you OPEN such a file and then re-WRITE it to another file with a lossy algorithm, that second version of the file may actually have lost some detail from the first one. You do not propose to do this, so don't worry.
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February 12, 2011 3:38:26 PM

Paperdoc said:
Almost no chance. The huge advantage of digital data storage over analogue is that a copy of a digital file is EXACTLY the same as the original (unless there is data corruption, which is rare and usually detected immediately). Unlike analogue copying, a copy of a copy of a copy of a copy ... in the digital world is still the same as the original. That is, as long as the file writing is done in a lossless manner.

You say you are using a lossless format for the original file. Once that is done, a copy of that file is identical to the original. Where confusion can arise is with software that does allow minor detail loss, and is used repeatedly. For example, some software to write photos in .jpg format allows for lossy storage to decrease file size. Merely copying such a file does not change the contents. BUT if you OPEN such a file and then re-WRITE it to another file with a lossy algorithm, that second version of the file may actually have lost some detail from the first one. You do not propose to do this, so don't worry.


Thank you for the detailed reply. I have a few other questions. What would be an example of an analogue source? Tape recorder? Also I have heard that digital data when moved or copied is transferred exactly as it was, or not at all. Do operating systems such as Windows 7 have built methods of verify the data has been transferred/copied to its exact form? Also if the Sata cable were physically loose on the connector would I get any data loss without knowing it? I thank you in advance.


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a c 342 G Storage
February 12, 2011 4:43:35 PM

Analogue signal examples: vinyl records, tape recordings, videotapes (not digital tapes), microphone output to an amp, amp output to a speaker, Composite Video TV signal (on the yellow line), stereo audio (left / right on red / white lines).

One task built into ALL computer systems is that, when any data are written to medium, an error-checking value called a checksum is also computed and written along with the group of data (on a hard disk, this "group" is one sector of 512 bytes). Then, any time it is read off again, the checksum is recalculated and compared to the stored value to verify that the data on the disk sector was written and read correctly. Now, that merely checks on the mechanics of writing data and reading it. In addition, most OS's (like Windows) these days also have routines that read back from a disk every time they copy and store some data and compare it to the original file contents to be sure the stored info is exactly what as in the original file. In the very old days this was a manual step run by the computer user with a DOS command called "verify", but now it's automatic.

With these procedures built into the OS and supporting hardware, you can be pretty confident a copy of a digital file is exactly the same as the original. If you REALLY want to be sure, you can get File Compare utilities, but most people don't worry about that.
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