pre-emphasis and archiving and cdda2wav

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krabapple
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pre-emphasis and archiving and cdda2wav

Postby krabapple » Wed Sep 29, 2004 1:23 pm

This is a fairly arcane subject but I thought I'd pass along my findings in case anyone's interested. I think Luke addressed this on Hoffman's forum some years back.

I've been archiving my CDs to lossless FLAC. One issue that comes up is that a few old CDs -- only classical discs, in my experience -- had a pre-emphasis bit encoded in them. Pre-emphasis was an EQ curve that used to be applied to recordings. Players recognize the pre-emphasis bit and apply the complementary de-emphasis accordingly...it's like the LP RIAA curve situation. (Exact Audio Copy can tell you whether a disc has pre-emphasis or not - though IIRC the thread Luke was in on SHtv involved claims that the Toshiba Abbey Road was preemphized, even though EAC said it wasn't)

If you archive a disc as an image -- say, one big file with a cuesheet-- then the pre-emphasis bit is retained, no problem (assuming your player is equipped to recognize it automatically, and I think most still are). But if you archive track by track, as I do, then it's lost, and playback EQ is incorrect (treble boosted). So I had to find something that would apply the de-emphasis curves during the archiving process. After some searching, the only tool I found that could do it in a PC environment was cdda2wav, running from the command line. (cdda2wav started as a unix-based CD ripping tool, but it's been ported to Windows as well. ). On the command line one uses the -T flag to apply a de-emphasis curve to the track as it's ripped to .wav. (there's also a -paranoia flag to do error-checking, for those of an EAC mindset).

So far it's worked like a champ for me, after some initial fiddling to get it to recognize my CD drive. Ideally I'd like to be able to take a .wav I ripped using EAC and run it though cdda2Wav -T, but that doesn't seem do-able -- you have to start with a CD. Or, at least, I'm not enough of a computer whiz to figur eout how to feed cdda2wav some .wav files, instead of CDA. The few cdda2wav GUI front-ends I've tried, btw, do not allow setting the -T flag -- if anyone knows of one that does these things, please tell me. Even better would be if EAC itself could apply de-emphasis, sidestepping the need for cdda2wav completely.

So to recap, for those who care, my archiving system on a Windows XP Home platform is:

EAC (to check CD for pre-emphasis) -- if absent, continue with high-security EAC-->FLAC

if present --> rip tracks to .wav using cdda2wav -T -paranoia-->FLAC
Last edited by krabapple on Thu Feb 24, 2005 2:05 am, edited 1 time in total.
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Patrick M
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Re: pre-emphasis and archiving and cdda2wav

Postby Patrick M » Wed Sep 29, 2004 1:48 pm

krabapple wrote:(Exact Audio Copy can tell you whether a disc has pre-emphasis or not - though IIRC the thread Luke was in on SHtv involved claims that the Toshiba Abbey Road was preemphized, even though EAC said it wasn't)

Isn't this also true for the old blackface Harvest DSOTM?
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Postby krabapple » Wed Sep 29, 2004 2:02 pm

Could be -- I don't have that one. It would be nice if there was a database somewhere of known 'pre emphasized' CDs. One of the Toto CDs seems to be complained about a lot, for being pre-emphed.

If EAC says a disc has no pre-emphasis, when it does, then comparing a track from the original (on a device that recognizes pre-e subcode) to the copy of that track made with EAC, should reveal a distinct treble boost in the latter. The problem is, how to show that objectively....

I forgot to add that another solution to de-emphazing rips is to use the 'Waves Q' plugin equalizer when ripping, which apparently has a de-emphasis setting. However, AFAICt this bugger costs something like $300!
Last edited by krabapple on Thu Feb 24, 2005 2:06 am, edited 1 time in total.
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Postby lukpac » Wed Sep 29, 2004 2:31 pm

What type of archiving are you doing, and for what purpose? If it's to create a "clone" of the original, why would you apply PE? My thought has always been to leave the data alone, and let the player deal with it. You can always just add the flag back manually while burning if that's an issue.

Of course, if you plan on *listening* to those files, then that's another story.
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Postby krabapple » Wed Sep 29, 2004 2:49 pm

What type of archiving are you doing, and for what purpose?

Those files are for listening as well as archive. Some apps allow manually toggling de-e playback for tracks that are known to be pre-e -- but obviously that's not acceptable for, say, playing tracks randomly from a playlist made up of tons of non-emphasized and a handful of pre-emphasized tracks.


If it's to create a "clone" of the original, why would you apply PE?

PE is 'applied' to individual tracks if ripped to .wav -- that is, the pre-emphasis EQ is preserved. But AIUI there's no way to automatically detect that it's been applied, and thus no automatic de-emphasis.

My thought has always been to leave the data alone, and let the player deal with it. You can always just add the flag back manually while burning if that's an issue.


I dont' see how I could add the subcode back to the individual tracks, when burning them. The only way to preserve the pre-emphasis *detection* it is to 'clone' the disc as a whole, AIUI.
Are you saying I could make a cuesheet for a compilation and add the flags there?
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Postby lukpac » Wed Sep 29, 2004 2:54 pm

krabapple wrote:I dont' see how I could add the subcode back to the individual tracks, when burning them. The only way to preserve the pre-emphasis *detection* it is to 'clone' the disc as a whole, AIUI.
Are you saying I could make a cuesheet for a compilation and add the flags there?


Exactly. You can even mix and match PE and non-PE tracks on a disc, IIRC.
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

Phil Elliott
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Re: pre-emphasis and archiving and cdda2wav

Postby Phil Elliott » Thu Sep 30, 2004 8:07 am

Patrick M wrote:
krabapple wrote:(Exact Audio Copy can tell you whether a disc has pre-emphasis or not - though IIRC the thread Luke was in on SHtv involved claims that the Toshiba Abbey Road was preemphized, even though EAC said it wasn't)

Isn't this also true for the old blackface Harvest DSOTM?


Yup - I've got one of those. My DAT machine doubles as the DA converter, and it brings up the empahasis indicator. Same thing with my old 10-track Dylan's Greatest Hits.
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Patrick M
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Postby Patrick M » Thu Sep 30, 2004 11:14 am

Phil, just wanted to say that I really enjoyed your solo on "Photograph"! Cheers.
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Postby Phil Elliott » Thu Sep 30, 2004 12:59 pm

My "photograph" in last month's Sound On Sound is far more impressive.
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Postby Xenu » Thu Sep 30, 2004 4:39 pm

Xenu is confused by these references.
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Postby Patrick M » Thu Sep 30, 2004 6:34 pm

"Phil Elliot" is a combination of guitarist Phil Collen's first name and vocalist Joe Elliot's last name. Phil Collen played the "Photograph" solo.

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Postby Kjoerup » Sun Oct 03, 2004 8:24 pm

Krabapple, I use Missing Media Burner, which is pretty much a command line port of cdda2wav (among other things) for use on Mac OSX. Now I don't have any CDs with pre-emphasis (as far as I know), but I can think of a workaround that may or may not work for you on Windows.

On OSX, you can use a program like Toast (what is the Windows equivalent? Easy CD Creator or something like that? I assume it works similarly to Toast) to mount a virtual CD on the desktop. Just create a play list with your wave files in Toast/Easy CD Creator, save as disc image and then mount it on the desktop. From there, you could have cdda2wav rip it just as it would any physical CD.

I know from experience this works on OSX. I'm not familiar with Windows to know if it's possible to do this, but I imagine it would be.

Hope this helps.

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Postby Xenu » Sun Oct 03, 2004 8:33 pm

Kjoerup, serious question: do you find OSX to be easier to work with than Windows?

I ask simply because Macs are theoretically supposed to be the "easier" alternative to PCs...more user friendly, blah blah blah. Yet with the advent of OSX--pretty Unix, really--that's all taken a turn for the byzantine. I work for U of C's Residential Computing department, and the consensus seems to be "sure, Macs are easier...except if they break, in which case kiss a day goodbye".
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Postby Kjoerup » Sun Oct 03, 2004 8:56 pm

I ask simply because Macs are theoretically supposed to be the "easier" alternative to PCs...more user friendly, blah blah blah. Yet with the advent of OSX--pretty Unix, really--that's all taken a turn for the byzantine. I work for U of C's Residential Computing department, and the consensus seems to be "sure, Macs are easier...except if they break, in which case kiss a day goodbye".


I'm really not sure what they mean by "if they break, kiss a day goodbye". I assume that may be a statement from techs familiar with DOS but vague about UNIX?

The UNIX underpinnings of OSX function completely invisibly for the majority of OSX users. Most will never even see a command line or will even know where to turn on the terminal -- and they'll never have a need to. Beginning with OS 10.2 (they're currently on 10.3), the OS is incredibly stable and trouble-free. I find it much better than Windows -- particularly the messy nightmare that is XP, but the question of preference is subjective, of course -- depends on your uses, your needs, what you feel comfortable with, etc. In the end, the computers all do pretty much the same thing, don't they?

For my own uses, the applications I use the most are MOTU Digital Performer (music production) and Final Cut Pro (video editing) -- both of which are Mac only, and I've yet to see any Windows audio or video programs that seem half as intuitive and trouble-free, at least to me. Software/hardware integration is invariably seamless with Mac (a huge plus) -- I just can't be bothered searching for drivers, then trying to get them to work with XP.

On the other hand, a really good 2-channel audio editor for OS X is lacking. I can't stand Peak, but like most Mac users, have little choice but to use it. It gets the basic job done, but can't hold a candle to a Windows-only program like Sound Forge.

In other words, Mac is right for me, and I prefer it. (I also have a cheap Windows box, which I use mostly for net surfing; I'm using it right now to look at this forum.) Someone else may think otherwise.

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Postby Kjoerup » Sun Oct 03, 2004 9:42 pm

I really think that the method I proposed above would be the least troublesome, Krabapple. From what I understand, all wave editors can only approximate correcting the 10dB high end boost of pre-emphasis; one would just be screwing up the EQ if he/she went the wave editor route.

The pre-emphasis flag is found in the PQ subcode data area of each individual CD track (not in the TOC of the CD). Obviously, exporting the individual track as a .wav or aiff file strips out the PQ subcode. (Krabapple knows this already; I'm just trying to make this coherent for those trying to follow the thread, so bear with me.):

[url=http://www.roxio.com/en/products/toastwithjam5/faq.jhtml#8]
Q. What is PQ subcode editing?
A. Audio CDs have 8 channels of non-audio data interleaved with the audio data. These channels (channels P through W) can contain graphics, or other non-audio data. Specifically, channels P and Q contain a variety of codes that may be required for commercial audio CD production. Jam fully supports PQ subcode editing including:

Time codes - Including where the track starts and stops, and absolute and relative time information.

UPC/EAN codes - Every commercial audio CD can have a unique product identifier code assigned for commercial purposes.

ISRC (International Standard Recording Code) - Each track on a CD can include identifying information about the track's author, country of origin, and year of production.

Pre-emphasis - This code is flagged to correct for a 10dB boost (to compensate for high end loss) that may have been applied to a digital file that was converted using an older digital to analog converter.

Copy-prohibit - If this code is flagged, it indicates that a track should not be copied, although it must be noted that most digital audio copy systems ignore this flag.[/url]

As Krabapple mentions above, exporting an individual CD track as a .wav file preserves only the audio data. The PQ data tracks are ignored, so you're left with a sound file with a 10dB high end boost and no flag to tell the decoder to de-emphasize it. CD creation programs like Jam or CD Architect allow you to input PQ subcode info, but those are strictly for creating CDs. It won't change the audio data, it merely adds the proper flag so the CD player will know what to do with the track.

The only real solution is to get rid of the 10dB curve altogether and never have to worry about pre-emphasis again.

If I had Krabapple's dilemma, I would go with the playlist --> virtual CD --> cdda2wav -T option method. If mounting a virtual CD (and getting cdda2wav to recognize it; that program seems really picky about things like that) isn't viable, I would just burn the wave files you need to de-emphasize onto a CD-RW as an audio CD, then have cdda2wav extract it (using the -T option) as it would any other disc. It may be a bit of a pain to do that, but this would work without having to obtain additional software, etc. The saving grace would be, I'd imagine, that you can't own too many CDs with pre-emphasis, correct? If it's only a handful, then you could re-use the CD-RW for this purpose, and not have to needlessly waste CD-Rs. At least with this method, you'd end up with correctly EQ'd FLAC files.