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  #15  
Old 2007-07-15, 11:53 AM
Tubular
 
Re: EAC configuration, offsets, etc...

The Coaster Factory has more complex examples on how to do it in the "Determining the Offsets Part II" guide, but I have found through reading and experimentation a very easy, simple way to determine the read offset for any drive, if you already have another drive in which the read and write offset is known. First decode a FLAC or SHN set to wav that has no sector boundary errors or other errors in a len check. This method won't work if the FLAC or SHN set has SBEs or other errors, because EAC extracts without adding SBEs or other errors every time, whether there were errors on the original files that were burned to audio CD or not. Burn an audio CD of these wavs with EAC with the write offset corrected.

You can determine the write offset of your read offset corrected drive by decoding a FLAC set to wav, then burning with the write offset set to (0). Then extract a wav with EAC with the read offset corrected to a different folder. You may have to enable or disable the "overread into lead in and lead out." Sometimes there are problems with the first and last track of a disc, so use a wav from the middle for best results (drive or EAC can't overwrite into lead in/lead out 100% correctly?). Then use EAC's compare wavs feature and compare the extracted audio CD's wav with the original FLAC > wav from your hard drive. You will get a numerical sample value, and this is the write offset of the drive. Enter this value (positive or negative, I'm not sure) into the write offset correction field of EAC, and then burn another audio CD with EAC, this time the write offset will be corrected. Then extract a wav(s) from this burned disc. Sometimes there are problems with the first and last track of a disc, so use a wav from the middle for best results (drive or EAC can't overwrite into lead in/lead out 100% correctly?). You may have to enable or disable the "overread into lead in and lead out." The compare wavs feature report should say nothing, in other words, report no missing samples between the two wavs. All of the wavs should match using the compare wavs feature. You can prove that they match with md5s or FLAC fingerprints.

Then extract this write offset corrected audio CD with the drive that you want to determine the read offset for. You may have to enable or disable the "overread into lead in and lead out." Use a read offset correction of zero (0) in EAC. Now burn a data disc of the same FLAC or SHN set. Extract the FLACs or SHNs from the data disc with the drive that you want to determine the read offset for to a different folder. Decode these to wav. Now use the compare wavs feature of EAC, and compare these two:

1)any wav that was extracted from the write offset corrected audio CD using EAC with read offset correction zero (0) Sometimes there are problems with the first and last track of a disc, so use a wav from the middle for best results (drive or EAC can't overwrite into lead in/lead out 100% correctly?).

2)a data disc FLAC > extracted to hard drive > decoded to wav

You will get a numerical sample value, and this is the read offset of the drive. Enter this value (positive or negative, I'm not sure) into the read offset correction field of EAC, and then extract the audio CD again. Sometimes there are problems with the first and last track of a disc, so use a wav from the middle for best results (drive or EAC can't overwrite into lead in/lead out 100% correctly?). You may have to enable or disable the "overread into lead in and lead out" The compare wavs feature report should say nothing, in other words, report no missing samples between the two wavs. All of the wavs should match. You can prove that they match with md5s or FLAC fingerprints.

With this method you will be able to determine the read offset of drives that are not in EAC's drive database, and without a CD that is in EAC's CD database, provided you have another drive that is read/write offset corrected. Maybe members from TTD can mail out write offset corrected audio CDs and data FLAC discs to people who can't correct their own drives, and don't have another drive that is read/write corrected. Then using these discs, they can configure their drives proplerly.

Wouldn't it be much easier if the original Red Book specification for audio compact discs and CD players was unencrypted wavs on CD-ROM ISO 9660 data discs? Just imagine, every audio CD ever home-burned and professionally factory pressed would extract easily with Windows' or Mac's built in software and would be a perfect match of the original FLAC fileset every time, with no offsets to worry about. Slightly less minutes of music would have fit on each disc though. 70 minutes instead of 80?
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