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EAC changes the EQ [moderation: only via pre-/de-emphasis], EAC alters sound
dreamliner77
post Oct 30 2005, 16:09
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Has anyone tried asking Andre about de-emphasis application in EAC?


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Pio2001
post Oct 30 2005, 23:56
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Is the emphasis in MP3 exactly the same thing as in compact disc huh.gif
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dreamliner77
post Oct 31 2005, 00:49
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I always assumed so.


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TheFodge
post Oct 31 2005, 19:38
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QUOTE (rutra80 @ Oct 30 2005, 12:01 AM)
Now it would be nice to have a free tool that can properly apply de-emphasis on WAVs securely ripped by EAC.

*


That would be the ideal solution. I definitely prefer EAC because of its precision and error detection abilities.
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ChiGung
post Oct 31 2005, 20:21
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QUOTE (TheFodge @ Oct 31 2005, 06:38 PM)
QUOTE (rutra80 @ Oct 30 2005, 12:01 AM)
Now it would be nice to have a free tool that can properly apply de-emphasis on WAVs securely ripped by EAC.
*
That would be the ideal solution. I definitely prefer EAC because of its precision and error detection abilities.
*

This command line sound file processor, Sox can do de-emphasis. Its standalone usage to do this is just "sox infile.wav outfile.wav deemph" If you pop sox.exe in Eac's directory it should be possible to pipe Eac's output through Sox on the way to the encoder, something like "commandline encoder: sox.exe - - deemph | lame --preset standard - outfile.mp3" -but it will take some fiddling to find the exact syntax.


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smz
post Nov 1 2005, 04:49
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But... does anybody knows if this emphasis (rarely) used on CD-AUDIO correspond to the RIAA curve used on vinyl LPs? Doesn't seems so.

Sergio


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ReD-BaRoN
post Nov 1 2005, 05:43
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Is it easy to tell if a CD has pre-emphasis or not? Should I be concerned about having to go back and listen all my older CDs to see if they need to be de-emphasised now?
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smz
post Nov 1 2005, 13:57
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QUOTE (ReD-BaRoN @ Nov 1 2005, 05:43 AM)
Is it easy to tell if a CD has pre-emphasis or not?  Should I be concerned about having to go back and listen all my older CDs to see if they need to be de-emphasised now?
*


Assuming you still have your original CDs, just open Exact Audio Copy, insert them in the drive and give a look at the rightmost column in EAC. It tells you if Pre-Emphais is used for each track.

Sergio


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rutra80
post Nov 1 2005, 17:46
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QUOTE (smz @ Nov 1 2005, 05:49 AM)
But... does anybody knows if this emphasis (rarely) used on CD-AUDIO correspond to the RIAA curve used on vinyl LPs? Doesn't seems so.
*

Also, I wonder if there's only one standarized curve for CDDA, by looking at LAME -e switch, there seem to be at least two kinds of emphases (emphasises? emphasizes? unsure.gif ).
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Pio2001
post Nov 3 2005, 00:24
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QUOTE (smz @ Nov 1 2005, 05:49 AM)
But... does anybody knows if this emphasis (rarely) used on CD-AUDIO correspond to the RIAA curve used on vinyl LPs? Doesn't seems so.
*


No, it has nothing to do with it. The de-emphasis curve for CD ranges from 0 to -10 dB according to the chart above, and the de-emphasis curve for vinyl ranges from +20 to -20 dB.

QUOTE (rutra80 @ Nov 1 2005, 06:46 PM)
Also, I wonder if there's only one standarized curve for CDDA, by looking at LAME -e switch, there seem to be at least two kinds of emphases (emphasises? emphasizes? unsure.gif ).
*


For CDDA, yes, but I don't think that CD emphasis and MP3 emphasis are the same.
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Alex B
post Nov 3 2005, 02:24
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I have previously used correction values from a 15/50us de-emphasis table for making rough adjustments with a software EQ. My table seems to be a bit different from the curve in the earlier post. I have no idea which one is correct. I guess the difference is not audible.

CODE
kHz 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
dB -0.0 -0.0 -0.0 -0.1 -0.1 -0.1 -0.2 -0.2 -0.3

kHz 1 2 3 4 5 6 7 8 9 10
dB -0.4 -1.3 -2.4 -3.5 -4.5 -5.4 -6.1 -6.7 -7.2 -7.6

kHz 11 12 13 14 15 16 17 18 19 20
dB -8.0 -8.2 -8.5 -8.7 -8.9 -9.0 -9.2 -9.3 -9.4 -9.5

As a test I tried if iTunes could be used as a de-emphasis tool. First I ripped a CD with EAC in single image wave file & cue sheet format. Then I used Alcohol 120% and mounted the wave file as a single track audio CD by using this custom cue file:

CODE
FILE "disc image.wav" WAVE
 TRACK 01 AUDIO
   FLAGS PRE
   INDEX 01 00:00:00

"FLAGS PRE" is the pre-emphasis flag.

After that I ripped this virtual disc with iTunes in wave format. Apparently iTunes used a de-emphasis correction and made a new corrected wave file. This corrected file can be used instead of the original wave file. It works fine with the original cue sheet. Though, the FLAGS PRE lines should now be removed.

I don't know how good the DSP equalizer used in iTunes is, but I can't hear any obvious problems. ABX testing is impossible because the original file is uncorrected.

Edit: typo

This post has been edited by Alex B: Sep 28 2006, 16:07


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smz
post Nov 3 2005, 03:38
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An interesting test (that I cannot do as I don't have, and don't want to have iTunes installed on my system), would be to burn a CD (or make a virtual image of it) with white noise or a frequency sweep, insert the PRE flag, rip with iTunes and compare the original.

From that one can see what equalization curve iTunes is using and eventually adopt it within Audition or any other software EQ.

Any voulnteer? rolleyes.gif

Sergio


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Alex B
post Nov 3 2005, 16:34
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QUOTE (smz @ Nov 3 2005, 05:38 AM)
An interesting test (that I cannot do as I don't have, and don't want to have iTunes installed on my system), would be to burn a CD (or make a virtual image of it) with white noise or a frequency sweep, insert the PRE flag, rip with iTunes and compare the original.

From that one can see what equalization curve iTunes is using and eventually adopt it within Audition or any other software EQ.
*

Here's a frequency sweep before and after the iTunes treatment:



Edit: fixed the image link

This post has been edited by Alex B: Aug 25 2007, 21:02


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smz
post Nov 3 2005, 16:45
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WOW! it is totally different and a lot "stronger" equalization that the one published in this previous post!

Edit: sorry, I missed that the base line was at -20 dB, so... maybe not that much stronger. Anyway I must now leave. Will give a deeper look ASAP...

Sergio

This post has been edited by smz: Nov 3 2005, 16:48


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markanini
post Nov 3 2005, 16:53
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QUOTE (smz @ Nov 3 2005, 05:45 PM)
WOW! it is totally different and a lot "stronger" equalization that the one published in this previous post!

Edit: sorry, I missed that the base line was at -20 dB, so... maybe not that much stronger. Anyway I must now leave. Will give a deeper look ASAP...

Sergio
*


No it's not. Read the graph values more carefully.
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Alex B
post Nov 3 2005, 17:06
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The file I used was recorded at -20 db. I didn't bother to fix the db values in the graph.

I checked the source of the table I posted earlier. It was this thread at EAC forum:

http://www.digital-inn.de/showthread.php?t=19034


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Bill02888
post Nov 6 2005, 13:24
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As I'm re-ripping my entire collection I came across something that might be of interest. The CD "The Digital Domain - A Demonstration" (1983) contains 4 tracks of pink noise:

"22 - Pink Noise @ -26 dB with emphasis"
"23 - Pink Noise @ -26 dB no emphasis"
"24 - Pink Noise @ -46 dB with emphasis"
"25 - Pink Noise @ -46 dB no emphasis"

Unfortunately EAC lists Pre-Emphasis as No for all 4 tracks.

Anybody interested in performing an analysis of these tracks?

- Bill
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Deep_Elem
post Nov 6 2005, 17:50
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After reading this thread I went and tried sox.exe to demphasize the few CDs that I have that were mastered with preemphasis. Sox does the job very fast and with excellent results. I've had sox for a long time but until now I'd only used it to convert some aiff files to wav. Thanks to the poster who pointed out a new use to me.
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Pio2001
post Nov 7 2005, 13:15
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QUOTE (Bill02888 @ Nov 6 2005, 02:24 PM)
  "22 - Pink Noise @ -26 dB with emphasis"
  "23 - Pink Noise @ -26 dB no emphasis"
  "24 - Pink Noise @ -46 dB with emphasis"
  "25 - Pink Noise @ -46 dB no emphasis"

Unfortunately EAC lists Pre-Emphasis as No for all 4 tracks.
*


If you have the old version of EAC with the "detect TOC manually" feature, try it. It may set the pre flags properly by reading them from the subchannels instead of the TOC.
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Alex B
post Nov 7 2005, 13:39
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QUOTE (Bill02888 @ Nov 6 2005, 02:24 PM)
Unfortunately EAC lists Pre-Emphasis as No for all 4 tracks.
*

Just rip with a CUE and add the PRE flags to the CUE file. When I tested the frequency sweep I used a custom CUE sheet. The sweep file itself was an old wave file from my archive without flags or tags whatsoever.


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Bill02888
post Nov 7 2005, 16:01
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QUOTE
If you have the old version of EAC with the "detect TOC manually" feature, try it. It may set the pre flags properly by reading them from the subchannels instead of the TOC.


Alas, I'm using the latest version of EAC, V0.95 beta 3.
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dreamliner77
post Nov 8 2005, 02:32
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QUOTE (Pio2001 @ Nov 7 2005, 08:15 AM)
QUOTE (Bill02888 @ Nov 6 2005, 02:24 PM)
  "22 - Pink Noise @ -26 dB with emphasis"
  "23 - Pink Noise @ -26 dB no emphasis"
  "24 - Pink Noise @ -46 dB with emphasis"
  "25 - Pink Noise @ -46 dB no emphasis"

Unfortunately EAC lists Pre-Emphasis as No for all 4 tracks.
*


If you have the old version of EAC with the "detect TOC manually" feature, try it. It may set the pre flags properly by reading them from the subchannels instead of the TOC.
*




I get the impression that these tracks don't use the flag, instead they are examples of what the difference in sound is.


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Weird Music Mafi...
post Nov 18 2005, 11:55
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Hi, guys!

I'm collecting classical CDs since the beginning of the CD era.

In my collection of ~ 5000 classical CDs I have discovered some 150 CDs with pre-emphasis so far (1 among ~33 - is this rare???).

Attention: It's often said that only recordings mastered before 1986 use pre-emphasis --> definitely wrong !!!
Some labels do use it just up to date (but not regularily) e.g. Erato and the Swedish label BIS (on almost every second CD) !!!

In short (I can only tell about classical, though) - which labels are suspicious to use it more frequently than others?

I never found any CD by Universal (Deutsche Grammophon, Philips, Decca...), RCA (BMG) or CBS/Sony (but that's no guarantee)
EMI didn't use it after 1987 (but Maazel's Zeffirelli-Otello soundtrack has it - besides this one I only got some CDs from EMI Japan with pre-emph).

Pre-Emph is (still !) used frequently on Supraphon, BIS, Erato, New World Records and other smaller labels - especially from Northern & Eastern Europe.
( I believe you'll find it often, too on smaller jazz labels...)

So pre-emph still remains a serious problem for ripping (because most people simply don't know about it)!
Best puzzles are CDs with mixed pre-emph status (some tracks on the CD have pre-emph, others not!). For a long time I was quite sure such CDs wouldn't exist anyway - but meanwhile I have discovered at least 2 examples of New World Records CDs with mixed status

There's a simple (but precise) free tool available developed by an acoustics engineer (Mr. Ahlersmeyer) to de-emphasize pre-emphasized audio data (so we could do compressing, converting, releasing - all we need afterwards).

It's just great, of course better than the often recommended WAVE 10 band equalizer Q10 - an equalizer can only give an approximation to the de-emphasis curve. Mr. Ahlersmeyer uses exactly the mathematics needed. You need the VB5 runtime libraries installed to your system. The tool is available as freeware here:

http://www.picosound.de/Waveemph100a.zip

Mr. Ahlersmeyer says that the tool wouldn't run under XP --> it does (you have to choose Win98 compatibilty modus though, else you would indeed get an overflow error).

Unfortunately the tool produces an overflow error, too, if the original CD data contains exactly 100% peaks. The only workaroung at the moment would be to normalize to 97% before using the tool...

So - if you want to produce compressed audio from a pre-emphed CD, try the following procedure: smile.gif

1). Open the CD with EAC and figure out if the PRE-Flag is set
2). Extract the digital audio with EAC - > Copy Image & Create CUE Sheet
3). Apply Waveemph100a to the extracted .wav
4). Split the de-empasized WAV to separate tracks with EACs Tool -> Split WAV by CUE Sheet
5). Produce your mp3s (oggs... whatsoever) from the single tracks...

If you want to archive a CD as a whole (for burning later as CD Audio - not for listening on the PC!) it's sufficient to use EACs
- > Copy Image & Create CUE Sheet -> compressed
because EAC produces correct cue-sheets with the Flag PRE lines (many other rippers don't).

Attention: NERO (even V.7) simply ignores the PRE-Flag in an audio cue sheet (even when burning an image) and doesn't set the bit on the burnt audio CD.
So never burn an audio CD image of a CD containing pre-emph with Nero!
(This is a real shame - only if you will be using Nero's plain Copy CD function the PRE-Flags are preserved!). crying.gif
Burning with EAC itself of course will produce perfect copies (I would like to know which alternative burning proggies do evaluate the PRE-Flag of an audio CD cue correctly - please post your experiences).

This post has been edited by Weird Music Mafia: Nov 20 2005, 14:34
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SebastianG
post Nov 18 2005, 14:32
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Out of curiosity: Is there any place on the web showing the magnitude response of a proper de-emphasis filter ?

All I ever saw was some kind of analogue circuit which is supposed to do the de-emphasis filtering, but hey ... I've no clue how I should generate a digital filter from something like that -- Also I can't find it right now, nor any good description about such filters via google / wikipedia.

BTW: I once saw an older proposal for storing PCM audio on a DVD with optional (digital) pre/de emphasis. Did this make it into the official standard or did they ditch that ? Does somebody know ?

Sebi

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fredhammersmith
post Mar 22 2008, 04:57
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Wow! Resurrecting a very old thread, but I'm just discovering the joys of pre-emphasis...
Now. I was preparing my big move to a music server and I already copies 400 of my CDs on my HD, using EAC, with cue sheets. The I did The Wall, my 1979 copy. Pre-emphasis. 1st time.
What I would like to know is:
is there any utility program that can perform a earch on all my CUE sheets to check if the FLAGS PRE appear?
I've tried the Search function of XP, with no success.
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