Spectral Comparisons.pdf

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12.10.2013 Spectral Comparisons

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CD image downloaded fromFreeFoto.com

The EA C guides are written byxuncat, all screenshots by xuncat(Febr uary 2008 - September 2009).

This work is licensed u nder aCreative Co mmons Attribution-Noncommercial-Share Alike 3.0Unpo rted License

EAC Gui des Home

Back To Index

EAC 1.0 Setup Guide

EAC 1.0 Rippin g Guide

Guide Contents

1. Introduction: losslessand lossy formats

2. Spe ctral view

3. FLAC

4. LAME

5. Ogg Vorbis

6. Transcodes

Other EAC Guides

EAC Installation Guide

EAC Setup Guide

EAC Lossy Setup Guide(mp3 and Ogg Vorbis)

EAC Ripping Guide

EAC CD Burning Guide

Useful Links

EAC Homepage

FLAC Homepage

1. Introduction: lossless and lossy formats

This is not a guide. This section is here in order to visually show you thedifference between the different kinds of files treated in the EAC guides. Itends with a brief e xplanation of w hat t ranscoding is and why t ranscodingnormally is a bad thing to do.

Our point of de parture is the wave file: the .w av file that EAC produces asyou rip an audio CD track. To be sure, .wav is really a container format thatcan hold different kinds of audio; in this case the cont ent of the .w av file is"really" PCM audio.

If you have ripped t he CD properly, in accordance w ith the guides, the.wav file contains exactly the same audio data as the original CD. Wave filesare rather large, t hough, which makes them awkward for transfer and/orstorage. Th is is whe re FLAC enters the picture. It stands for "Free Lossless

Audio Codec". It compresses the audio data without removing any of it, just like Zip and RAR compress data withou t removing any of it. T his is whyFLAC is properly called a lossless format. With the right kind of cue sheet,you can re-create a copy of your CD from your archived FLAC files any time.

Lossy formats can save space by removing some audio data, for example bycutting down on the number of kilobits used per second of audio and/orremoving "unnecessary" audio data according to some algorithm, in additionto compressing the files. This way the files can be made much smaller, butthere is always a trade-off between audio quality and file size.

A common standard for "accept able" audio quality for mp3s is 128 kbps. Itis a constant bitrate (CBR) sett ing that you see, for example, with mostiTunes downloads (though t hey make use of the FhG encoder, not thesuperior LAME encoder for mp3). Ogg Vorbis has been developed to focuson quality measures rather than bitrates, but a rough equivalent to mp3 at128 kbps would be the q3 setting.

Others claim that the threshold for "transparency" (where you can't tell thedifference from the o riginal) would be at 192 kbps for mp3s, and q6 (oreven q5) fo r Ogg V orbis. For LAME mp3, the re is also t he variable bitrate(VBR) preset V 2 (t arget bitrate ~190) that w ould be the "transparent"

VBR set ting. (Variable bitrate , used in both the Ogg Vorbis -q preset s andthe LAME mp3 -V presets, means that the encoder analyses the audio dataand only uses as high bitrate as is needed, i. e. lower bitrate for lesscomplex (or silent) parts of the audio data.)

The pictures below are intended to show you the differences betw eendifferent formats and bitrate set tings, from "best possible" to "transparent"to "acceptable".

2. Spectral view

The pictures are screenshot s taken while using the " spectral view" in

Adobe Audition (v. 1.5). T he spe ct ral view is a way of making some audioproperties visible. The screenshots show you the two stereo channels withthe left channel on top. T he ho risontal axis is for time, the vertical axisshows the frequency of the audio data for each channel. The coloursindicate the amplitude: from dark blue for the lowest decibel (softest)sounds to bright yellow for the highest decibel (loudest) sounds.

These screenshots show a maximum of 22 kHz for each channel. That isbecause we are looking at CD rips with t he standard frequency of 44 .1 kHz(combined for bot h channels). Other recordings, such as some soundboardtapes or vinyl rips, may go much higher.

All the screenshot s, except tw o of the FLAC one s, are for t he same track:"I Feel You" from Depeche Mode's Songs of Faith and Devotion . That is areasonably complex audio t rack t hat serves to illustrate t he differencesbetween the different encodings. The LAME mp3 and Ogg Vorbis fileswere created from the FLAC file using dBpoweramp.

3. FLAC

Spectral Comparisons
http://blowfish.be/eac/Spectral/spectral.htmlhttp://blowfish.be/eac/index.htmlhttp://creativecommons.org/licenses/by-nc-sa/3.0/http://flac.sourceforge.net/http://exactaudiocopy.de/http://blowfish.be/eac/Burn/burn.htmlhttp://blowfish.be/eac/Rip/rip1.htmlhttp://blowfish.be/eac/Lossy/lossy.htmlhttp://blowfish.be/eac/Setup/setup1.htmlhttp://blowfish.be/eac/Install/install1.htmlhttp://blowfish.be/eac/Spectral/spectral.htmlhttp://blowfish.be/eac/Caaok/caaok-eac-2.htmlhttp://blowfish.be/eac/Caaok/caaok-eac-1.htmlhttp://blowfish.be/eac/index.htmlhttp://creativecommons.org/licenses/by-nc-sa/3.0/http://creativecommons.org/licenses/by-nc-sa/3.0/http://validator.w3.org/check?uri=refererhttp://www.freefoto.com/preview/11-12-9?ffid=11-12-9


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Accurate Rip Homepage

DAE Drive FeaturesDatabase

The HydrogenaudioKnowledgebase

EAC Helper

First out is the original FLAC file - if it we re deco mpressed t o W AV (PCM) itwou ld still look exactly the same. (In fact, any file you ope n in Audition is"converted" t o W AV in order to show the waveform.) As you can see, itgoes all the way up t o 22 kHz. The file size is 31.2 MB; the decompressed.wav file w ould be 46.3 MB.

FLAC (I Feel You, Depeche Mode) 31.2 MB

The following two pictures are here in order to illustrate that CD rips willlook different depending on the source and the kind of music. The first oneis a recording originally made in 1937, digitally remastered from the analoguemaste r in 2000. It's the small jazz group Benny Goodman Quartet (clarinet,piano, vibraphone and drums) playing "Tea For Two". This is what old andmost new acoustic recordings will look like. In ot her words, there is notnecessarily anything w rong with a CD rip t hat do es not show audio data allthe way up to 22 kHz per channel. The second picture drives this facthome: it is Mitsuko Uchida playing t he rondo from Mozart's KV. 545,recorded digitally in 1984 by Philips' finest.

FLAC (small group jazz, 12.9 MB)
http://eachelper.atwebpages.com/http://wiki.hydrogenaudio.org/index.php?title=Main_Pagehttp://www.daefeatures.co.uk/http://www.accuraterip.com/


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FLAC (classical solo piano, 6 .6 MB)

4. LAME mp3

LAME mp3, starting with the highest CBR setting, 320 kbps. The frequencyhas been cut off at 20.5 kHz - that is one reason for the comparatively smallsize. Another reason is the removal of some "unne cessary" audio data, thatyou can see in the stripey character of these pictures as compared to theoriginal FLAC. The V 0 t hat follows should be equal in sound quality t o t he320 kbps CBR, but it is smaller in size because lower bitrates have beenused for less complex parts of the audio, and the frequency maximum is at19.5 kHz. Also, in the V0 you can see a "shelf" cut-off at 16 kHz, that ismore pronounced in the "transparent" V2 (max frequency at 18.5 kHz),and prominent as a clear cut-off for t he "acce ptable" 128 kbps CBR.

LAME mp3 320 kbps (I Feel You, Depeche Mode) 10.8 MB


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LAME mp3 V0 (I Feel You, Depeche Mode) 8.8 MB

LAME mp3 V2 (I Feel You, Depeche Mode) 6.6 MB

LAME mp3 128 kbps (I Feel You, Depeche Mode) 4.3 MB


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5. Ogg Vorbis

Ogg V orbis can go up to 500 kbps, and it thus has a higher "best possible"quality than mp3, illustrated here by the q10 set ting. Ogg V orbis uses adifferent algorithm from mp3, and doesn't cut off the frequency for thehigher quality settings: both the q10 and the "transparent" q6 shown herehave more or less audio data preserved at 22 kHz, though much less for theq6. T he "acce ptable" quality q4, still reaches roughly 19 kHz, but you canclearly see that some audio data is missing, compared to the original FLAC.

Ogg Vorbis q10 (I Feel You, Depeche Mode) 15.4 MB



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6. Transcodes

So, encoding to lossy formats gives you the advantage of small file size atthe price of losing some audio data. This simple fact should be enough t oexplain why you can not encode such files again, and ge t h igher qualityaudio files. You simply can not regain lost audio data, not by increasing thebitrate, and not by converting to another format.

The quality will actually decline in lossy to lossy encoding, even if you try to"increase" the quality by encoding to a higher bitrate, since the algorithmfor removing "unnecessary" audio data is applied once again. If you encodefrom lossy to lossless, the quality will stay exactly the same, only the file sizegets bigger. See the screenshots below. Yes, they look very much like themp3 128 and the V0 above, respectively, but these really are screenshotsof t ranscodes.

Do not ever do it.

128 kbps LAME mp3 transcoded to 320 kbps LAME mp3 (I Feel You,Depeche Mode) 10.8 MB


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V0 LAME mp3 transcoded t o FLAC (I Feel You, Depeche Mode) 30 .4 MB

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