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CD Recording FAQ
7. AudioCD
7.3. Making a perfect AudioCD copy
It is very easy to to copy an audio cd like any other cd and still have satisfying results. This means that you can listen to the copy without noticing any audible difference from the original, and, as a matter of fact, decent hardware and software will be sufficient for this task.
However, if you are a perfectionist and want a copy which will be an accurate reproduction of the original, you have to follow a slightly complicated procedure, which envolves a few steps.
7.3.1. What is needed
To make a perfect AudioC copy you need:
The first two have to do with the hardware, the other two with the software.
The basic requirement overal is:
The first is possible using programs which
will re-read a sector if needed, like EAC or CD Paranoia. The second is
inherent to all readers and writers of decent quality. At this point it must be emphasized that a reliable writer will write
gaps between tracks precisely. For example, a gap of 2.00 will be written
as such, and not as 1.99. The same holds for a reliable reader. Often
poor design or just age do not permit such accuracy. If this happens,
it is a bad sign for your drive.
7.3.2. The procedure
First of all, you have to ensure that your hardware is adequate for this task. This is the case if you can extract audio and the extracted wav files are always the same.
Before reading further, please note that offset correction has a meaningful importance when an audio cd gives birth to a number of generations, as it happens in live recording trading circles, where the offset error would otherwise be multiplied with each new generation. Otherwise, if you just make a copy of an audio cd it is rather unlikely to be of any importance, unless you are a perfectionist.
The next step is to determine the offset correction necessary. The head of the drive reads starting at position, say, 998 when instructed to start at position 1000. This introduces the offset error, which has to be calculated. Keep in mind that when you use a specific reader-writer pair, you have to find the combined offset value. Also, you have to find this by testing your own hardware instead of relying upon values found by others, since even drives of the same model may not have the same offset.
To find the offset, you have to make a copy of an audio cd. Then, you have to extract a track from the original and the same track from the copy using the same drive for this, and perform a binary comparison of the two wav files (or even open them with a HEX editor). You will notice that the two files are equal except that they have a different number of zeros at their start. By counting these bytes you determine the offset correction necessary.
After that, you can use this value for the specific hardware combination to produce a CUE sheet and an image of the original cd which you can burn.
7.3.3. An example using EAC
The procedure described above can be automated using appropriate software. Under Windows, you can use Exact Audio Copy, which is a free program able to rip and write audio cds.
To start, insert a cd into the reader and start EAC, making sure you use it in Secure mode. From the Action menu, choose Copy Image & Create CUE Sheet. EAC will the rip the whole cd into one file and then create an accompanying CUE sheet.
When done, insert a blank cd into the reader and choose Write CD-R from the Action menu.
At the CD Layout Editor, load the CUE sheet you created. All information contained in it will appear in the CD Layout, as shown in the following screenshot:
When done with writing the new cd, place it in the cd reader and extract a track, then do the same with the original and the same always track. Select Compare WAVs from the Tools menu and let the program perform a binary comparison of the two files.
After the 2 files are binary compared, you will see the differences that were found between them. If you only see a statement like "109 repeated samples", then you are almost done. If you see more differences, then the ripping process was not reliable.
Suppose that you got a statement like "109 repeated samples" which means that the offset was found to be 109. If there are extraneous samples in the file ripped from the copy, then the offset is positive, otherwise negative.
At this point, you have to fill this value into the Offset/Speed tab of the reader's options in EAC.
Now you have to repeat the process of copying an audio cd using the same procedure and see if the files extracted from the original and the copy are completely indentical. If you have done everything right, then they will be indentical.
Once finished, all you have to do every time you want to copy an audio cd is to select Copy CD from the Tools menu and follow the simple dialogs which follow.
