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I purchased some SACD content from a website..., Can SACD have been accurate ripped?
nycjv321
post Aug 29 2010, 15:41
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As the title explains, I bought an SACD online or atleast a ripped one at 96khz, 24bps. But in the tags there are 2 tags of interest "ACCURATERIPDISCID" and "ACCURATERIPRESULT"....... Are there SACDs in the accurate rip (I thought it was CD-only not SACD as well) database? Also if this is the case, if I post one the IDs of a track here where could I get it verified? If it was in fact a regular audio cd? or in fact the original SACD? (The tags say the ripped with "conidence 10)
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Cavaille
post Aug 29 2010, 15:53
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QUOTE (nycjv321 @ Aug 29 2010, 16:41) *
As the title explains, I bought an SACD online or atleast a ripped one at 96khz, 24bps. But in the tags there are 2 tags of interest "ACCURATERIPDISCID" and "ACCURATERIPRESULT"....... Are there SACDs in the accurate rip (I thought it was CD-only not SACD as well) database? Also if this is the case, if I post one the IDs of a track here where could I get it verified? If it was in fact a regular audio cd? or in fact the original SACD? (The tags say the ripped with "conidence 10)


Because of strong copy protection it is currently impossible to "rip" a SACD. To be precise, it is impossible to rip the SACD layer while it is possible for every drive to rip the CD layer. Therefore I assume that the audio from the material you bought was derived from the CD layer and perhaps upsampled later. Ive also bought some titles from for example HDTracks.com - so far Ive never seen a tag that hints to the use of Accurate Rip. But it could also mean that someone simply changed the tag. A frequency response of the material you bought could shed some light into this.


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nycjv321
post Aug 29 2010, 16:01
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How can I post a screenshot here to show the metadata from foobar2000?
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spoon
post Aug 29 2010, 16:56
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I have seen also...very odd:

http://forums.linn.co.uk/bb/showthread.php...=84417#pid84417


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2Bdecided
post Sep 1 2010, 11:05
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Maybe the least cynical answer is that someone just copied the tags over from a CD rip?

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skamp
post Sep 1 2010, 12:09
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Ripping a SACD is not impossible, it just involves hardware hacks.


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nycjv321
post Sep 1 2010, 14:16
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Well I emailed then the website directly, and they responded that the metedata is produced by the record label and they have no control over it..... so I dont understand why would a record label be using accuraterip metedata?
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spoon
post Sep 2 2010, 11:29
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Record Labels will rip cds just like anyone else, all (or most) those discs on iTunes Music Store were ripped from cds.

My self I would be looking at an FFT of the frequencies (spectrogram) to see if there is anything above 22KHz

This post has been edited by spoon: Sep 2 2010, 11:30


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nycjv321
post Sep 2 2010, 16:02
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QUOTE (spoon @ Sep 2 2010, 06:29) *
Record Labels will rip cds just like anyone else, all (or most) those discs on iTunes Music Store were ripped from cds.

My self I would be looking at an FFT of the frequencies (spectrogram) to see if there is anything above 22KHz



How can I do that? Also if it is resampled will it still show data above that frequency?
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db1989
post Sep 2 2010, 16:10
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Using a spectral view in an application like Audacity, EAC, etc. There was even a 'quick spectrum view' app advertised here a while back, but I don't recall its name.

And no, unless the resampling was done horrifically badly, there will be no higher frequencies added.
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nycjv321
post Sep 2 2010, 23:40
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Ok, I used audacity, and I tested three tracks in audacity with the built-in spectrum analyzer.

For the album originally questioned, as suspected, stops at 22khz.......

I tested another "HD Album" and it seems to go up to about 44khz on a 96000hz scale (audacity spectrum was zoomed out all the way and was mostly full, so this is normal right? and can I get explanation for this? or could someone tell me how to post an image here? so I can show a screenshot). I tested another song that was an ogg file (cd rip @ 44.1khz) and it stops at 22khz (audacity won't let me zoom out any further....) so yea it seems that that audio that was supposedly "hd" is only a cd rip that was upsampled... I emailed the website after their original response and they said that they would "investigate it further" I suspect that that isaac hayes album from that link posted above is also a resample of a cd...

This post has been edited by nycjv321: Sep 2 2010, 23:41
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pdq
post Sep 2 2010, 23:51
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QUOTE (nycjv321 @ Sep 2 2010, 18:40) *
I tested another song that was an ogg file (cd rip @ 44.1khz) and it stops at 22khz (audacity won't let me zoom out any further....)

A file whose sample rate is 44.1 kHz cannot have content above 22.05 kHz, so that is why you couldn't zoom out any further.
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nycjv321
post Sep 2 2010, 23:54
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QUOTE (pdq @ Sep 2 2010, 18:51) *
A file whose sample rate is 44.1 kHz cannot have content above 22.05 kHz, so that is why you couldn't zoom out any further.


I have seen this in several posts on this forum, may I have some explanation as to why? please get scientific if needed, I'm just trying to understand the technology better.


This post has been edited by nycjv321: Sep 2 2010, 23:59
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pdq
post Sep 3 2010, 00:05
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If you only sample a signal at 44.1 kHz, then any frequency higher than 22.05 kHz will be aliased to a frequency below 22.05 kHz. For example, if the signal frequency is 23.05 kHz then when you sample it you will get instead a signal at 21.05 kHz.

Since frequencies above 22.05 kHz cannot be represented in a 44.1 kHz samples file, to display anything above 22.05 kHz makes no sense.
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nycjv321
post Sep 3 2010, 00:09
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What do you mean by aliased?
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pdq
post Sep 3 2010, 00:23
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Picture a sine wave. If you sample the wave several times per cycle then you get a digitized representation of the sine wave and you can reproduce the original waveform from the digital data.

Now picture what happens as the sampling interval gets longer and longer until you are only sampling the sine wave a little more than twice per cycle. You can still reproduce the original sine wave, but you need to observe it for multiple cycles so that you eventually get samples over the entire waveform. the closer you get to sampling twice per cycle, the more cycles you need to observe, until to get to exactly two samples per cycle, which doesn't give you enough information to deduce what the original waveform was.

Now if you sample slightly less than twice per cycle you once again see the sampled data varyingso as to sample over the entire waveform, but the sampled data are now indistinguishable from those you would get from a similar waveform that you sample slightly more than twice per cycle. This is called aliasing because frequencies above half the sampling frequency appear as the mirror image of the real spectrum.
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kisli
post Sep 3 2010, 08:00
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QUOTE (nycjv321 @ Sep 3 2010, 01:09) *
What do you mean by aliased?

Found this link in HA Knowledgebase:
http://www.dsptutor.freeuk.com/aliasing/AD102.html
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2Bdecided
post Sep 3 2010, 10:09
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Google for Nyquist and find everything you could ever possibly want to know, and far more besides!

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David.
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Arnold B. Kruege...
post Sep 3 2010, 11:26
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QUOTE (nycjv321 @ Sep 2 2010, 19:09) *
What do you mean by aliased?


Due to the way sampling works, signals whose frequency is equally spaced away on either side of half the sampling frequency produce the same set of samples,

For example, we commonly sample audio at 44,100 Hz. Half of that or the Nyquist frequency is 22,050 Hz.. We find that 22,000 and 22,100 Hz produce the same data when sampled. They are thus aliases for each other. This problem is commonly resolved by filtering the input signal so that no signal at or above 22,050 is sampled.
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