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crc results question.
diypig
post Mar 28 2008, 17:56
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my confusion: hi, so lets say i rip a cd with one burner, flac and cue style, and then do the same cd but with another burner, should there be the same crc hash? is the hashes are different, how can they both be lossless?
i am probably not understanding something here... but could someone explain it please?
or should a certain cd always give a certain crc, for a wav at least, and then different people will get a different crc due to their pc encoding the wav to flac under slighty different condtions?
help! thank you very much.
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greynol
post Mar 28 2008, 18:01
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Offsets again: this time it's on the writing side.


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diypig
post Mar 28 2008, 18:10
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what? writing? i'm ripping. or am i confused again?
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greynol
post Mar 28 2008, 18:15
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You said burner, but it looks like I'm the one who's confused.

Do me a favor and post a log for a rip with each drive so I can explain what's going on. Be sure to put them in a codebox (syntax:<codebox> ... </codebox> except use [] instead of <>).


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diypig
post Mar 28 2008, 18:35
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i meant drive yeah!
ummm.... i deleted my old drives copy, so hmmm..
but if i rip a cd to flac and cue then rip it again the exact same way (same drive), can i get different crc's with them both being lossless/as accurate as each other?
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greynol
post Mar 28 2008, 18:38
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No.


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diypig
post Mar 28 2008, 20:15
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so it's ok to get different results?
(the way i asked my question made it confusing to know what yes or no means in the situation..)
but thank you!
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greynol
post Mar 28 2008, 20:24
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I guess I need to clarify:

No, you cannot have different CRCs when ripping with the same drive (and same method of CRC calculation and with offset correction unchanged) with both versions being accurate. If the CRCs are different then at least one of the rips will not be accurate.

This post has been edited by greynol: Mar 28 2008, 20:27


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diypig
post Mar 29 2008, 17:35
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you are god. thank you.
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diypig
post Nov 17 2012, 22:56
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adding on from this, sure it is old, but it is mine, and the the same information remains smile.gif
so, adding on from that, the offset of the drive would matter in the cry of RIPPED files?
do you mean the offset correction unchanged, so, it being changed (and now not correct) would give you incorrect rips? (that makes sense).

and, when the wav file is compressed to flac, say using level 8, the resulting crc would be the same each time? i think i may have asked this once upon a time but i cannot find it. thank you.

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Cynic
post Nov 18 2012, 02:41
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I'm not sure if I understood your questions but I'll try to answer them.

QUOTE (joshuatm @ Nov 17 2012, 21:56) *
so, adding on from that, the offset of the drive would matter in the cry of RIPPED files?
Yes, if you change the read offset in the drive you will get ripped files with different CRCs.

QUOTE (joshuatm @ Nov 17 2012, 21:56) *
do you mean the offset correction unchanged, so, it being changed (and now not correct) would give you incorrect rips? (that makes sense).
It would give ripped files with different CRCs from the ripped files you would get with the "correct" read offset for the drive. The rip may still be considered accurate if you use something like CUETools to verify the rip against the AccurateRip database, since, all other things being equal, the audio data would only have been shifted by a few samples (similar to a different pressing of the CD).

QUOTE (joshuatm @ Nov 17 2012, 21:56) *
and, when the wav file is compressed to flac, say using level 8, the resulting crc would be the same each time?
If you compress a wav file to flac, and then decompress that flac back to wav, the CRCs of the audio data of the two wav files will be the same, because flac is lossless. If you use a lossless codec, you can compress/decompress as many times as you wish and the audio CRC will never change.
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diypig
post Nov 18 2012, 09:21
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thank you for your time and answers, sorry if i was a bit confusing.

what i meant is, if i use one drive, with a different offset (yet, it is the 'correct offset' for that drive), and another drive, with a different correct offset, but yet again, correct for that drive, both drives would rip the same wave files, with the same crds (hopefully, provided everything went well)
i think i just answered my own question smile.gif

and, yes ok, i understand that part, being lossless, flac -> wav etc, but say i compress a wave with a flac, and another day, a different computer maybe, i compress that same wave to another flac, using the same compression settings. those flacs themselves, do they necessarily have the same crc?
i understand when you covert them back to wav that they will/should have the same crc, but, in flac, would they?
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greynol
post Nov 18 2012, 13:21
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The flacs themselves can be different depending on machine doing the compression (ex: AMD vs. Intel). This appears to have been the case with previous versions, at least. If they decompress the same I don't see that it matters all that much.

This post has been edited by greynol: Nov 19 2012, 15:40


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diypig
post Nov 19 2012, 08:22
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ah ok, sure, well thanks for the information!
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