# iTunes encoding quality



## GadgetLover (Dec 11, 2001)

OK, so I'm considering re-encoding my CD's into 192k mp3's.  I presently have them encoded for my personal listening pleasure (love my Nomad JukeBox baby!) at 128k.  Is this necessary?  A good idea?  A must?  While I still will keep them encoded at 128k for my mp3 player (so I can listen to more tunes), I was considering re-encoding at a higher quality bit-rate for "near CD quality" listening via my home stereo system.  What do you all suggest?  I have a lot of mp3s so re-encoding will: (a) take a loooong(!) time and (b) take double the space (gigs!) but se la vie if necessary.

Also, when (if ever) do people encode at HIGHER than 192k?  If a CD is 650MB and you can get it down to 65MB (128k) it makes great sense if the sound quality is good enough.  If you can get it down to 130MB it still makes sense (192k).  But at some point (260MB, 325MB??) it is lame (no pun intended) -- less quality but not much less size.  At some point in the argument, one might as well just 'rip' the CD into AIFF and leave it at that.

So, you audiophiles out there, please comment ....


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## ScottW (Dec 11, 2001)

I just finished encoding around 200+ songs tonight at 192. It is NOT double the size by any means, only slightly larger. I think 192 sounds great, but Im not a music junkie either.

Admin


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## GadgetLover (Dec 11, 2001)

I have not tried encoding at 192k but my friend did and said it was about 2.1 times bigger than the 128k file.  Is that not true?  Can someone tell me how big 10-20 songs are at 128k AND 192k (for comparison)?

Also, what is the difference between "joint stereo" and "stereo"?

Finally, do you 'customize' your encoding and--assuming that you all encode at 192k--turn ON "variable bit-rate encoding"?  Is this necessary?

I am trying to create the best overall settings to encode ALL of my CD collection into mp3s -- so it will take up ALOT of space on my hard drive but it will be worth it (to some degree of space sacrifice) to get the quality out of it.  I like the idea of using my Mac as a jukebox rather than manually switching between CDs every time I want to listen to different artists/songs.


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## halli (Dec 11, 2001)

I listen to music with iTunes through my stereo system so I need good quality, 128 bit was too low but I can hear no difference between 160 bit and 192 bit (but a huge difference between 128 bit and 160 bit) so I encoded my whole music library in 160 bit and my 124 hours of music takes only 8,1 GB of space (about 1,1 MB per minute)


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## GadgetLover (Dec 11, 2001)

Thanks for your input Halli!

Halli's comment regarding listening to encoded music through a HIGH-FIDELATY STEREO SYSTEM (not SoundSticks!) brings up a good point here:

If anyone replies in this forum regarding listening to mp3s on such a stereo, please include what type of stereo system you have (generally) ... for example, Halli reported that s/he heard no noticeable difference between 160k and 192k encoded mp3s but a big difference between 128k and 160k.  And this may be quite true for Halli but not true for someone with a higher end hi-fi system (I used to think "hi-end" meant more than $500 for a receiver ... until I listened to such components costing more than $5,000 dollars (and up).  Same with speakers... I used to think $250 (pair) 3-way speakers sounded great, then I thought that $250 (each) speakers sounded greast, then I listened to $500 (each) tower speakers (etc) ... until a friend took me to a store in Los Angeles (read: store for celebrities and rich folks only) where--believe it or not--they sell speakers costing as much as $80,000 (EACH!!).  (A waste of money if you asked me, but then again, I'm not Bill Gates.)  So, as they say, "it is all relative."  Alas, this brings me to my point: the more info the readers have about what someone's listening components are the better their informed decision will be on whether or not they will likely notice any difference in quality.

... and if you ARE Bill Gates (or Steve Jobs, Shaq, or George Lucas) then please don't reply 'cuz we all know that our systems suck compared to yours and we don't care!  Cuz we have no intention on selling our clothes, cars or homes just to buy a fancy tin can that has sound coming out of it -- I'd rather listen to the radio.


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## dricci (Dec 11, 2001)

Most of my MP3s are 128 and sound fine (to me anyways) going thru my analog MidiLand subwolfer and speakers that come out of my iMac's audio out port. Haven't tried hooking it up to my stereo directly yet, but I have burnt some audio CDs from 128 MP3s and they sound fine on my surround sound stereo, too. I guess it's just how sensitive your ears can pick up


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## julguribye (Dec 11, 2001)

Wow! You like to write!

I encode them after how much I think I'm gonig to listen to them.
192 for most. 160 for less. I can't hear much difference, though.


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## GadgetLover (Dec 11, 2001)

> _Originally posted by julguribye _
> *Wow! You like to write!*



  I am trying to keep this forum focused and organized, as I think that this is information that many people are interested in.  When this forum is 'closed' I will try to get it moved to the FAQ forum.


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## shatfield1529 (Dec 11, 2001)

Speaking of encoding a CD collection, does anyone have a good method for smoothly ripping a collection of about 130 CD's? I would like to encode my collection, but would like to also limit the amount of time I spend sitting and waiting in front of my computer.

I've heard of 200 CD and 400 CD, um, things that you just put the CDs on a rack like, um, thing and it automatically loads one CD, rips it, takes it out, and goes to the next one. 

I've also heard of scripts that have been written that rips a CD into AIFF tracks, spits out the CD, and encodes it into MP3 as the next CD is ripping. Sounds smooth, but I haven't been able to find anything like it that worked with MacOS X.1.


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## chemistry_geek (Dec 11, 2001)

I personally record all my MP3's at 320kbps.  I know it may be overkill but I like the detail.  A typical 5 minute-ish song/track is around 11 to 13 MB.  I read many years ago that MP2 was a better sounding but lacked the compression of MP3.  I think I could tell the difference before (listening through $150 german headphones), but now I don't think I can hear the difference between the 320kbps MP3 and 320kpbs MP2.  Perhaps the encoding schemes are better for MP3 than they used to be, I don't know.  I remember downloading a command line MP3 encoder for OS X that claimed to encode using better psycho-acoustics than current MP3, but I never used it, got filled under some directory somewhere and archived to a CD, probably never to be used, but nice to have "just in case".

I wouldn't recommend re-encoding unless you have to.  For me and my CD burner, I can copy an audio disk faster than encoding MP3, but I only make my MP3 for my use and no one else's.  I had hoped to connect my Mac to my home stereo but never did.  I didn't for fear of being disappointed in the sound quality coming from the Mac.  My home stereo cost about $10,000 and I expect to hear serious flaws, which I wouldn't be happy with so I didn't even bother.  Incidently, you can hear the difference between an original audio CD and the burned copy of an audio CD - the difference is due to timing errors that are introduced into the CD and picked up by D/A converter.

My stereo system:
High-end Philips (Made in Denmark) purchased 10 years ago from Paragon Sound in Toledo OH.

FR930 Receiver/amplifier($550; 150W/channel, Dolby ProLogic [when it was new!]).

CD 950 Compact Disc Player ($640; Frequency range: 2Hz-20kHz; Dynamic range: 108dB; Signal to noise ratio: >115dB; Channel separation: >110dB; Total harmonic distortion: 0.001%; Bitstream conversion 128X oversampling, 1 bit, 3rd order noise shaper).  This unit contains a commercial laser.  I will die before the laser burns itself out.  Optical digital output goes directly to the DCC digital input.

Digital Compact Cassette (DCC) recorder/player (records in MP2 format, sound specs not as good as the CD player).  Cost $1000 - yeah, I know, waste of money, right after I purchased it CD-R were introduced on the market.

BostonAcoustics VR960 speakers (Made in America; $1000/pair, 50 lbs each with one 8 inch powered sub in each speaker, Dolby Digital inputs, 1 inch Lynnfield tweeter, 4.5 inch mid range.  Speakers rest on 2 inch long spikes going into my carpeted floor.  http://www.bostonacoustics.com
http://www.bostonacoustics.com/ProductsPage.asp?ProductID=9&SpecID=1&SeriesID=16

Transparent Cable Music Link interconnects (Made in America; connects the CD player to the amplifier).  These cables are approximately 3/8 inch think and are made with high purity copper with high pass and low pass filters that terminate at the cables end in a small black box($150/pair).  Only frequencies in human hearing range are allowed to pass through the cables.  http://www.transparentcable.com

Transparent Music Wave speaker cable (Made in America; connects amplifier to speakers).  These cables are approximately 1 inch THICK, have high purity copper with high pass and low pass filters that terminate at the cables end in a large 7 inch black box($870/pair).  Only frequencies in human hearing range are allowed to pass through the cables.  Cables are only 10 feet long.  http://www.transparentcable.com

Bang & Olufsen turntable.  ($550 WITHOUT the diamond needle).  For VINYL records!!!  MM4 Eliptical diamond cartidge ($100).  The MM1 diamond cartridge was $500 - too expensive for me.

Other components will not be listed.  This is long enough.

When I listen to my music, I don't just hear it, I FEEL it, literally, the bass is incredible, but not overbearing - very tight bass.  

chemistry_geek


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## GadgetLover (Dec 11, 2001)

> _Originally posted by chemistry_geek (from another thread) _
> * I get between 5.8X to 6.3X MP3 encoding. When importing, the computer does not do any other tasks.
> 
> iTunes MP3 Encoding direct from the Preferences:
> ...



You're just the type of audiophile that I wanted to hear from.  I have a friend that has an even higher end system than yours (believe it or not) and he says some of the same things you have.  So, I have been trying to figure out the middle ground between QUALITY and QUANTITY of my mp3s.  Can you explain more about the mono v. stereo thing? Can you lower the mono part without effecting ANY of the sound quality in stereo?? I, too, could care less if my files do not have the ability to be played on a monoral system but I DO care that no quality is lost by reducing the mono channel to 8k (as you did) instead of (160k -- 1/2 of 320k). I can't believe that you can encode at 329k that many songs and have it only be 10GB. I have 2,000 songs encoded (at 128k) and it is 8GB.  Does the mono thing affect it that much?  Cool, if so.  Also, can you explain the joint v. normal stereo thing?


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## chemistry_geek (Dec 11, 2001)

GadgetLover:

A buddy of mine spent $20,000 ON A USED Proceed system (from eBay) after listening to the difference between Transparent interconnects and the cheap interconnect cables that come with every home stereo.  His system at the time was Harmon Kardon purchased from Circuit City.  He sold it on eBay and bought the Proceed preamp, CD-transport, a separate D/A converter, and a 100 lb Mark Levinson amplifier, with tranparent cables better than mine, piece by piece.  His speakers cost $5000/pair and are made in England - forgot the name of that manufacturer.  He too is a chemist in the polymer industry making bookoo bucks.  His system makes mine sound like it was purchased at a K-mart bluelight special in Hicksville USA.  It is a humbling experience to be out done by one-upmanship.

I cannot afford to keep up with the Jones's.

chemistry_geek


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## chemistry_geek (Dec 12, 2001)

Moving Picture Experts Group (MPEG) Homepage:

http://mpeg.telecomitalialab.com/

The inventors of MP3 (according to MPegger author):
http://www.iis.fhg.de/

MPegger is currently listed on versiontracker under Mac OS.

chemistry_geek


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## chemistry_geek (Dec 12, 2001)

MP3 encoding differences.

Direct from MPegger Documentation (credit goes to that author):

Stereo  - Encodes each channel as a separate stream. For example, if you encode a 128kbps stereo file with this set, it will actually encode two 64kbps streams, one for each channel.

Joint Stereo - Looks for similarities and differences in the two channels, and encodes them as one stream. This results in better sound quality, although it may not work with some MP3 players.

Layer III Constant Bitrate (CBR) - Encodes the file as an MP3 with a specified amount of data per second. This is the most compatible mode.

Layer III Variable Bitrate (VBR) - There are 3 types of VBR encoding: Normal Quality (NQ), Extra Quality (XQ), and High Quality (HQ).

chemistry_geek


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## GadgetLover (Dec 12, 2001)

> _Originally posted by chemistry_geek _
> *Stereo  - Encodes each channel as a separate stream. For example, if you encode a 128kbps stereo file with this set, it will actually encode two 64kbps streams, one for each channel.
> 
> Joint Stereo - Looks for similarities and differences in the two channels, and encodes them as one stream. This results in better sound quality, although it may not work with some MP3 players. *



Chemistry Geek (read: God):

So are you suggestion that the best overall setting (considering size too) is 8kbps (mono) / 320kbps joint stereo?  And should I do CBR instead so it is compatible with my systems?  My DVD player reads mp3s -- does it read VBRs?  What about the Nomad JukeBox and iPod?


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## chemistry_geek (Dec 12, 2001)

GadgetLover:

Well, I know that I've always used 8kbps (mono) / 320kbps joint stereo every since I obtained iTunes.  I had no idea what "joint stereo" was until I read about it from MPegger's documentation I downloaded 10 minutes ago.  The only thing I changed as far as iTunes encoding MP3 from the default setting was to minimize the monoaural audio stream's quality and to maximize the stereo audio stream.  This is the 8kbps (mono) / 320kbps stereo setting.  I didn't change any other settings for fear of messing up the quality in ways I didn't know about yet.  Turns out leaving the joint stereo checked was better, according to MPegger's documentation.  It would be nice if Apple actually provided COMPLETE documentation with their products so we would all know what these settings meant.  I have yet to find a help file on my system that explains every setting in iTunes.  In minimizing the monoaural audio stream and maximizing the stereo audio stream I (probably falsely) assumed that it would be less taxing on the CPU as it I thought it would / might be decoding audio I was not hearing or it was just throwing away.  I was just looking to maximize the audio quality of my system while removing any inefficiencies from the MP3 decoding process.  Who knows, I could be completely wrong about the 8kbps (mono) / 320kbps joint stereo setting, but it works for me.  God knows Mac OS X is slow enough on my system I wouldn't want to burden the processor with any more worthless chatter.

Regarding the CBR setting, I don't know what you mean by compatibility with your other systems.  Regarding your DVD player and Nomad Jukebox and iPod, you would have to check the documentation that came with your hardware.  You may have to do some tweaking with encoding settings to get your MP3's to work with all those devices (if they don't already) with just one MP3 file type.  As far as size is concerned, the 320kbps MP3 files can get large, and hard drives are cheap now so I'm not concerned with storage considerations.  I'm after total quality when it comes to listening to my MP3 on my BeyerDynamic DT150 german headphones - I can still differentiate  a 320kbps MP3 and the CD in the Mac.

The best advice I can give is that the 8kbps (mono) / 320kbps joint stereo setting works very well for me.

As an example, Charles Dickens "A Christmas Carole" narrated by our favorite Star Trek Captain, Patrick Stewart (Jon-Luc Picard) is a 2 CD set.  Disk 1 is 48:07 and 110.2MB; Disk 2 is 58:51 and 134.8MB.  BIG FILES!!!  Even if you are into pirating MP3, which I'm not, it would be out of the question to share/ steal files of this size on LimeWire or other file sharing programs with a 56K connection.  Your chances of getting disconnected from your ISP are greater than obtaining the file in its entirety.  At 320kbps, I think this is purely an individual preference, you don't have to use that setting.

chemistry_geek


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## beef (Dec 12, 2001)

Joint stereo sometimes introduce artifacts...  If you aren't concerned about the space, I'd encode at 256kbps, stereo.  I wouldn't bother using VBR.  It doesn't really save that much space.

you can use lame to encode mp3 with iTunes.

---
edited (addtion)

forgot when, but 300 'audiophiles' tested the quality of mp3 with original cd, 128kbps mp3, and 256kbps mp3.  They picked out 128kbps mp3's 90% of the time...while most times 256kbps passed.  They used quality audio equipment at studio, so it's not Fisher's bullshit boombox.  and mp3's were decoded on Macs (encoded on PC though)

so if you're after quality, I wouldn't go with 128kbps.

If you are using lame, you can use JS.  It's better than others.  If there's too much separation, it'll just use stereo for that frame..  I dunno what encoder iTune uses.


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## Essage (Dec 12, 2001)

...a song encoded in 192kbps takes up 1,5 times of what a 128kbps does.

But I'd say it's really worth it.

I´s easy to calculate the size of an mp3. kbps stands for "kilo bit per second". 128kbps takes up 0,96MB/min, (128*60)/8=960
192kbps takes up 1,44MB/min, (192*60)/8=1440
320kbps takes up 2,4MB/min, (320*60)/8=2400

128kbps sounds really bad. 160 is ok, but not good, can still hear some distorsion. While I think 192 is really good. It´s the best compromise between size & sound. So I rip all my CD´s in 192. But if there´s a really good song that I know I will listen to the rest of my life (almost), I rip it in 256.

I have a Sony STR-DB940 DD/DTS Reciever (about 650$, awardwinning), a Sony ...-XB930 CD Player(400$), and Audio Pro Black Diamond speakers (500$/pair, very priceworthy).


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## GadgetLover (Dec 12, 2001)

OK, so new sub-poll:

For those of you audiophiles that prefer higher quality encoding, which do you prefer (again, keeping in mind quality vs. size sacrifice)?

a) 192kbps, stereo (96kbps per channel);
b) 256kbps, stereo (128kbps per channel);
c) either 192 or 256 (above) but in JOINT STEREO;
d) 320kbps, stereo
e) 256 or 320 but with mono set to 8kbps (as Chem Geek suggests -- I've never tried it).

In other words, has anybody else done the mono reduction thing?

And what about the custom settings in iTunes -- if you encode at higher than 192kbps, you must use them, so what should the "smart encoding" and "filter frequences below 10hz" "channel (auto, stereo, etc)" be set at??


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## Myke (Dec 12, 2001)

As a Hi-Fi obsessive who has now become a Mac obsessive too, I say forget MP3, if you want quality.

ANY kind of compression will be audible with even a half decent hi-fi.

So, what we are talking about is compromise - and you trade off quality for size.

Anything above 160 is going to give you sufficient quality not to wince, but you'll still flatten the sound and the high frequencies will lack energy.

At best, your MP3's will sound like they are playing on a mini-disc, which use a similar kind of compression.

Some high end hifi can make the music sound sweet, just the same (valves usually) - but on more analytical gear you can hear graininess, akin to pixellation on JPEG photo files.

Did someone mention B&O catridges by the way? Wish we could stll get the good ones in the UK, they only sell the low end version here! The top of the line MMC was my favourite of all time.



Rogers e40 valve amp
Quad ESL 63 speakers
Audionote CD player
Dunlop Systemdeck turntale with Ortofon line contact stylus.

Oh ...and a G4 733


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## beef (Dec 12, 2001)

I agree to some extent...

I'm not an audiophile, and my stuffs (I wouldn't bother listing, unless requested) will prolly be considered mid-fi by real audiophiles...

so, can I hear the difference between CD and mp3?

actually yes, even at 256kbps... but in my opinion, that has more to do with the soundcard of my mac, the output (headphone out...) and the cable connecting mac and my preamp.

so if I'm listening to music, while doing nothing else (or little), I'd always use CD.  But if I'm listening to music as some background music while I do other stuffs, I can live with iTunes.  The advantage being I can just use a playlist, and don't have to change CD, etc...I can just keep working.

If I play CD or mp3 on my mac, they'd both sound shitty because the builtin speaker ain't worth a damn...

If you determine the quality of mp3 by how much difference from CD you can actually detect, then the equipment you use will have as much to do with the numbers, etc......

but...mp3 encoders are improving.. and ATRAC3 has come a long way, too...  I remember the first time I heard MD... it was just shitty.  My feeling was "smaller than tape, no-where near CD".  I dunno when was the last time you used MD, but it's alot better than that now.  I wouldn't mind using it now...as portable media.

in any case...  I've always felt it's your ears that must be satisfied... and as I've said, your equipment will affect how you come to your decision.  I "recommended" 256kbps stereo (ms if you're using lame), but the real solution probably is just to play around with a few of your favorite tracks...if you can hear the difference, then calculate the change in file size (total) and see if it's worth it...  if you can't hear the difference, then why bother.

anyone know what encoder iTunes comes with, btw?  I'd definitely encourage you to get lame encoder.

hmm.......I've always imagined it'll be easier to get that kinda stuffs in UK...  after all, alot of people go there to hunt for old records...  Quad 63...how long have you had that thing?  have you listened to the new quads?  nobody around here has one...


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## rezba (Dec 12, 2001)

Does your 128kbs mp3 let you happy earing them ? 
Sound is so related to your earing skill ! I have pretty good earing, compensing my deficient eyes. I noticed that 192 give me back a quite full sound with a 3 or 5 pieces sound system. But most of my friends don't ear the difference between a 128 and a 192.
I encode in 192 to preserve a good quality when a encode my mp3s in AIFF to play them on my hifi. When it's symphonic music, I try to catch 256 mp3. It's better. But it take to much place to do it systematicly.

However, does anyone ever eared the sound of a ATP 700 sound system. For a quarter price to the Harman Kardon, it's so.... waouh !


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## GadgetLover (Dec 12, 2001)

FYI (Fraunhofer is the inventor of mp3 technology along with Thomson RCA)

http://www.iis.fhg.de/amm/techinf/layer3/index.html

===
MPEG Audio Layer-3
History    Quality    Details

History  

In 1987, the Fraunhofer IIS-A started to work on perceptual audio coding in the framework of the EUREKA project EU147, Digital Audio Broadcasting (DAB). In a joint cooperation with the University of Erlangen (Prof. Dieter Seitzer), the Fraunhofer IIS-A finally devised a very powerful algorithm that is standardized as ISO-MPEG Audio Layer-3 (IS 11172-3 and IS 13818-3).
 
Without data reduction, digital audio signals typically consist of 16 bit samples recorded at a sampling rate more than twice the actual audio bandwidth (e.g. 44.1 kHz for Compact Disks). So you end up with more than 1.400 Mbit to represent just one second of stereo music in CD quality. By using MPEG audio coding, you may shrink down the original sound data from a CD by a factor of 12, without losing sound quality. Factors of 24 and even more still maintain a sound quality that is significantly better than what you get by just reducing the sampling rate and the resolution of your samples. Basically, this is realized by perceptual coding techniques addressing the perception of sound waves by the human ear.
 
Using MPEG audio, one may achieve a typical data reduction of
 
1:4    by Layer 1 (corresponds with 384 kbps for a stereo signal),
1:6...1:8    by Layer 2 (corresponds with 256..192 kbps for a stereo signal),
1:10...1:12    by Layer 3 (corresponds with 128..112 kbps for a stereo signal),
still maintaining the original CD sound quality.
 
By exploiting stereo effects and by limiting the audio bandwidth, the coding schemes may achieve an acceptable sound quality at even lower bitrates. MPEG Layer-3 is the most powerful member of the MPEG audio coding family. For a given sound quality level, it requires the lowest bitrate - or for a given bitrate, it achieves the highest sound quality.
 

Sound Quality  

Some typical performance data of MPEG Layer-3 are:
 
sound quality    bandwidth    mode    bitrate    reduction ratio
telephone sound    2.5 kHz    mono    8 kbps *    96:1
better than short-wave    4.5 kHz    mono    16 kbps    48:1
better than AM radio    7.5 kHz    mono    32 kbps    24:1
similar to FM radio    11 kHz    stereo    56...64 kbps    26...24:1
near-CD    15 kHz    stereo    96 kbps    16:1
CD    >15 kHz    stereo    112..128kbps    14..12:1
*) Fraunhofer uses a non-ISO extension of MPEG Layer-3 for enhanced performance ("MPEG 2.5") 
 

In all international listening tests, MPEG Layer-3 impressively proved its superior performance, maintaining the original sound quality at a data reduction of 1:12 (around 64 kbit/s per audio channel). If applications may tolerate a limited bandwidth of around 10 kHz, a reasonable sound quality for stereo signals can be achieved even at a reduction of 1:24.
 
For the use of low bit-rate audio coding schemes in broadcast applications at bitrates of 60 kbit/s per audio channel, the ITU-R recommends MPEG Layer-3. (ITU-R doc. BS.1115)
 

Details  

Filter bank
 
The filter bank used in MPEG Layer-3 is a hybrid filter bank which consists of a polyphase filter bank and a Modified Discrete Cosine Transform (MDCT). This hybrid form was chosen for reasons of compatibility to its predecessors, Layer-1 and Layer-2.
 
Perceptual Model
 
The perceptual model is mainly determining the quality of a given encoder implementation. It uses either a separate filter bank or combines the calculation of energy values (for the masking calculations) and the main filter bank. The output of the perceptual model consists of values for the masking threshold or the allowed noise for each coder partition. If the quantization noise can be kept below the masking threshold, then the compression results should be indistinguishable from the original signal.
 
Joint Stereo
 
Joint stereo coding takes advantage of the fact that both channels of a stereo channel pair contain far the same information. These stereophonic irrelevancies and redundancies are exploited to reduce the total bitrate. Joint stereo is used in cases where only low bitrates are available but stereo signals are desired.
 
Quantization and Coding
 
A system of two nested iteration loops is the common solution for quantization and coding in a Layer-3 encoder.
 
Quantization is done via a power-law quantizer. In this way, larger values are automatically coded with less accuracy and some noise shaping is already built into the quantization process.
 
The quantized values are coded by Huffman coding. As a specific method for entropy coding, hufman coding is lossless. Thus is called noiseless coding because no noise is added to the audio signal.
 
The process to find the optimum gain and scalefactors for a given block, bit-rate and output from the perceptual model is usually done by two nested iteration loops in an analysis-by-synthesis way:
 

*    Inner iteration loop (rate loop)
 
The Huffman code tables assign shorter code words to (more frequent) smaller quantized values. If the number of bits resulting from the coding operation exceeds the number of bits available to code a given block of data, this can be corrected by adjusting the global gain to result in a larger quantization step size, leading to smaller quantized values. This operation is repeated with different quantization step sizes until the resulting bit demand for Huffman coding is small enough. The loop is called rate loop because it modifies the overall coder rate until it is small enough.

*    Outer iteration loop (noise control/distortion loop)
 
To shape the quantization noise according to the masking threshold, scalefactors are applied to each scalefactor band. The systems starts with a default factor of 1.0 for each band. If the quantization noise in a given band is found to exceed the masking threshold (allowed noise) as supplied by the perceptual model, the scalefactor for this band is adjusted to reduce the quantization noise. Since achieving a smaller quantization noise requires a larger number of quantization steps and thus a higher bitrate, the rate adjustment loop has to be repeated every time new scalefactors are used. In other words, the rate loop is nested within the noise control loop. The outer (noise control) loop is executed until the actual noise (computed from the difference of the original spectral values minus the quantized spectral values) is below the masking threshold for every scalefactor band (i.e. critical band).


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## martek (Dec 13, 2001)

There will be a difference in sound quality between one bit rate vs another ... and between mp3 and CD.  MP3 is a lossy compression in which some of the data is always thrown out in the interest of file size.  Researchers are becoming more clever about *which* data can be tossed out while keeping the *perceived* sound quality relatively high.
It's rather irksome that the marketing droids affix the label "CD quaility" to mp3 devices/software when technically, it's not true.  CD "quality" is 16 bit, 44.1khz!   

I've done some experiments and have found 160k about the lowest bit rate I can stand to listen to music with.  Anything lower there's too many compression artifacts.  As a rule, if the CD sounds kinda crummy to begin with, I'll encode at 160, if it's a medium quality recording I'll select 192, and if it's a jazz or classical recording of high quality I'll choose 256 or higher.  I find these settings sound fine on my G3 with Boston Acoustics sat/sub 3-piece speakers that I use at work.

I also have an audio system at home comparable to some of the previous posters and I can say without a doubt that mp3 encoded audio sounds nothing like the original CD.  Depending on the music you can get acceptable results (comparable to the sound of FM radio I'd say) but nothing real great.  This may change in the future with more sophisticated compression algorithms that (hopefully) don't throw out any data.  If anyone cares (probably not, but I'll say it anyways  ) LP records still sound better than CD's.

Bottom line?  Go with what your ears tell you and don't worry about it.


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## Jadey (Dec 13, 2001)

I couldn't vote! I encode at 64 bit to stuff more into my rio


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## 2001pass-var (Dec 14, 2001)

"If anyone cares (probably not, but I'll say it anyways  ) LP records still sound better than CD's. "

I couldn't agree with you more!


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## beef (Dec 14, 2001)

> _Originally posted by 2001pass-var _
> *"If anyone cares (probably not, but I'll say it anyways  ) LP records still sound better than CD's. "
> 
> I couldn't agree with you more! *



and tubes are better!


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## GadgetLover (Dec 16, 2001)

> _Originally posted by beef _
> *
> 
> and tubes are better! *



Yes, vacuum tubes DO rock.  


Ok folks, so it looks like I'm going to re-encode ALL my CD's (that's a lot) at 192k (or 224k).  Wadda ya think?


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## Myke (Dec 17, 2001)

Beef - re your comments about the EL63's -  I have heard the new Quads and I don't think they are as good. Perhaps I'd get used to them if I had them at home for long enough ...

I'm not certain but I think that Quad continues to make the EL63 - mine aren't that old. 

Hardcore HiFi fans prefer the original Quad electrostatics!

Couldn't agree more about valves (as we quaint oldworlders call them!)


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## beef (Dec 18, 2001)

> _Originally posted by Myke _
> *Beef - re your comments about the EL63's -  I have heard the new Quads and I don't think they are as good. Perhaps I'd get used to them if I had them at home for long enough ...
> 
> I'm not certain but I think that Quad continues to make the EL63 - mine aren't that old.
> ...



hmm... interesting...  I knew there were shops that does repair, etc, for the original EL63's... but I wasn't aware that Quad still made those...

I guess I'd give Santa a call

and... yea... I have to agree... unless you can audition things at your own home for awhile... it's really hard to see how things fit in...


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## Jadey (Dec 18, 2001)

Tubes don't actually sound better, they have more resonance, and if you prefer more resonance in your music, you're going to enjoy tubes more. It's  subjective.


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## Myke (Dec 18, 2001)

I'm not sure what Jadey means by "resonance" - but I think it's a little more complex than that!

All the same it is true there's no 'right' answer in HiFi. The distortions involved in the recording process - such as  the aural signature of microphones, the ambience of the recording environment, the 'mix' and so on - mean that you never get to hear the original sound.

But - so what? Good HiFi is still a joy to listen to.

By the way, Beef, I think you may be confusing the EL63's, which came out in the 80's, with the original Quad speakers which were made in the 60's. 

The EL63's were definately on sale a couple of years ago when I last looked, alongside Quad's latest speakers, the name/number of which escape me.

Incidentally, can anyone explain why my G4/733 has an analogue audio output, but no input? I find the output pretty good, apart from a low level hum problem (I mean very low level)

However, using a music card like Protools Digi001 puts the Mac up there with the most expensive of HIFI.


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## thedbp (Dec 18, 2001)

I'm definitely an audiophile, and I've had my Mac hooked up to my surround sound system since day 1 ... and something I noticed that iTunes does that I haven't seen with other encoders is that it keeps the surround channel in audio CDs.  I was floored when I put on the Tool MP3s I had made from a friend's copy of Lateralus (I know I know I need to buy it but I'm broke) and heard distinctly the surround channel.  These were encoded at 160, and sounded great.

I re-encoded them at 192 a little while later, bumped the file size up considerably, but I didn't get that much better quality out of it.  Some of the toms stilll sounded weak to me, and the guitar/bass still bled together a little bit.  But overall, it sounded just dandy, better than tape quality at any rate, and isn't that what MP3s are here to replace more than anything?

My vote is 160, especially if you are limited in HD space.  I'm struggling with my 12GB drive ... i have X, 9 Classic, and 9 Main systems installed, plus all the apps?!?!  And VPC with a full install of Win2K?!?!  I don't have that much left to worry about the marginal difference in quality between 160 and 192.


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## beef (Dec 19, 2001)

uh...  isn't Tool Lateralus in STEREO?

if you select surround sound mode in your preamp, anything will come out in 5.1, 7.1, or whatever it supports... but the surrond channels won't have their own discrete sound... if the surround channels seem to have their own sound... i think that has more to do with the difference between your main and surround speaker, and other setup,etc...

but...I'm not an audiophile...and you say you're... so you probably know things I don't...  I'm not even sure about Tool's Lateralus encoded 2 channels only... and I own the damn thing (just never bothered to listen in surround...)  I'm more of a caveman when it comes to surround music...

...I've listend to some SACD, DVDA, etc... personally, I don't get this surround music...  I appreciate surround sound in Movies, etc... but I've never been to a place where I'm actually surrounded by the band.  Whatever concert, etc, I've been to, the band is always in front of me... I dunno about you guys, but it'll be a while before I'll get into surround music thing...  I'm not gonna listen to Stereo materials in surround either...  unless somebody here tells me how it's done right.

well...I've heard a lot of arguments when it comes to tube vs transistor... and I still use Musical Fidelity A3 (pre/amp) which I still think sound good... and transistors tend to have better numbers on test bench...and they produce less tonal harmonic distortions... but afaik, that distortion is high-order/odd-order...while the tubes produce (yea.....a lot more substantial...but...what's the word...soft?) even-order harmonic distortions... which one's more natural...which one never appears in music...?

I probably am biased after reading stuffs... but yea... things come down to personal preferences...  after listening to tube and transistor for awhile... I thought I preferred tubes (was I determined to believe tube sounded better...?  maybe... I dunno... I was proud of my stuffs, too though...). I prefer stereo for music... etc...

...so yea... whatever you prefer...

and about mp3... I still say encode with LAME (takes a lot of time though) at 192 or better...  there're links to lame's latest build and script that works with iTunes at macosx.com.
--edited
I recommended 192 or better, because I think gadgetlover mentioned he has 
Creative Jukebox thing.  I dunno how long he listens to music, but I personally think the battery would run out before he's done listening to everything in it... and I'm hoping he doesn't mind adding/deleting files in it occasionally.


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## scruffy (Dec 19, 2001)

The names of the encoding rate carry meaning:  at 128 kbps, mp3 files take up, unsurprisingly, 128 kilobits per second of audio.

128 kb/s / 8 b/B * 60 s/min = 960 KB/min
192 kb/s / 8 b/B * 60 2/min = 1440 KB/min = 1.4 MB/min

And so on.


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## kilowatt (Dec 19, 2001)

Tubes are better for listening to vintage music because:

1) The guys in the 60's were using tube amps in studios. They recorded, and listened using tube amps, so the music is almost made to be heard through tube amps.

2) Tubes are not flat-frequency. Tubes have a semi-variable compression based on frequency and volume (where as a digital compression algorithm pretty much ignores frequency - and I'm not talking about data compression, just audio compression). This compression yields a fatter warmer sound.

3) Tubes tollerate. You can easily blow out your friend's solid-state class ab amp in his boom box. No prob. But tubes can take abuse. 

4) Nuclear-blast resistance. In the event of an EMP from a nuke, most anything that relies on silicon as an electrical semiconductor will become useless. So if we get nuked, I'm gona crank up the music.. because I can!

In my studio, I use a rather large mixer and some Crown, Peavey, and Mackie amps. These amps have a much higher headroom than most home stereo gear, so you don't get any compression or loss of signal dynamics. 

When I want to hear my music, though, I use some custom class-a audio amps I built a while back. These use 12 6L6 tubes in class A configuration, and I use one of these amps for each of four channels (which I usually just run in stereo configuration). 

Do I use LP's? You bet! Well, untill those movers bonked my lp player... time to get another one I suppose.

I don't compress most of my music. Why? Well, if you have a 60gig hard disk, and are willing to set aside 20 gigs for music, thats... 650mb/disk... about 1gig for two disks... thats forty cds. Which accounts for 90% of the music I listen to. As a rule, I never compress Pink Floyd, Hendrix, or Classical/jazz music. 

Seriously, if you enjoy listening to music, go with what sounds best. I don't bother with gold connectors because I used my ossiliscope and a frequency alanizer, and I couldn't see any differnece between gold plated connectors and normal connectors... I do use balanced signal lines whenever possable, though.


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## mrfluffy (Aug 19, 2002)

> _Originally posted by thedbp _
> *My vote is 160, especially if you are limited in HD space.  I'm struggling with my 12GB drive ... i have X, 9 Classic, and 9 Main systems installed, plus all the apps?!?!  And VPC with a full install of Win2K?!?!  I don't have that much left to worry about the marginal difference in quality between 160 and 192. *


same here, except i've got 2gigs less and softwindows with win98


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## mindbend (Aug 19, 2002)

My recommendation for the re-encoding option is to only bother when/if you hear a track or album that you notice any issues with. If you're listening to your stereo passively I doubt you will have any problem with your current 128 quality. If you pop the headphones on or listen more carefully you will notice more aliasing.

I encoded all my CDs based on how much I liked the album. My favorite albums got the 192, most everything else got the 128 and the rarely listened to ones got the low end.

Audiophiles will be audiophiles, but anything beyond 192 for general listening is pointless. I've got a pretty nice set of critical listening monitors (Alesis Monitor Ones) and the 192s sounds excellent. If I need quality beyond that, I'll put the original damn CD in.


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## Paragon (Aug 21, 2002)

I encode my mp3's with stereo 160 VBR, quality high and standard stereo.

I have it all hooked up to my HiFi, a Cyrus dAD3 cd-player ($1400), Cyrus Straight Line amplifier ($670) and a Cyrus Power preamp ($800). All hooked up to my speaker's two System audio 1070 ($970).

...I LOVE my system.


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## mindbend (Aug 21, 2002)

Paragon...what possible humanly justification could there be to drop $1,400 on a CD player?


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## Paragon (Aug 21, 2002)

> _Originally posted by mindbend _
> *Paragon...what possible humanly justification could there be to drop $1,400 on a CD player? *



...well if you are into music as much as I am you really want something sounding good. I know it's a lot of money but I can't say that I've regretted it for a day. I guess people spend their money differently, for example I don't have a car I use a bike. I think spending $20.000 on a car is redicules, but that's just my opinion.


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## Paragon (Aug 21, 2002)

> _Originally posted by chemistry_geek _
> *My stereo system:
> High-end Philips (Made in Denmark) purchased 10 years ago from Paragon Sound in Toledo OH.
> *



...I didn't know that Denmark made Philips? Do you mean assembled in Denmark? I know B&O is mostly Philips.


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## chemistry_geek (Aug 21, 2002)

> _Originally posted by Paragon _
> *
> 
> ...I didn't know that Denmark made Philips? Do you mean assembled in Denmark? I know B&O is mostly Philips. *



Yes, the stereo system was MADE in Denmark.  I opened up the CD player.  The CD player circuit board was made in Denmark, as was the DCC Player.


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## mindbend (Aug 22, 2002)

Paraong,

I'm not trying to bait you or anything, I think it's cool you have a great system. I do find it ironaic though that you can drop god knows how much $ on the system, but you're encoding at only 160! I'm sure it sounds just fine, but if "just fine" were all you were looking for, a $99 CD player would do.


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## Paragon (Aug 22, 2002)

Actually I don't have that many mp3's, but the ones that I do have I play over my stereo. I buy my cd's instead because I think that it has superior quality. I don't do much encoding and usually it's just for checking the cd out before I buy it...or not.  

I will say though that it's not necessary to encode at a higher quality because of the small cable that is hooked into the mac, I wouldn't even be able to hear the sound improvement.


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## drash (Aug 22, 2002)

> _Originally posted by kilowatt _
> *Tubes are better for listening to vintage music because:
> 
> 4) Nuclear-blast resistance. In the event of an EMP from a nuke, most anything that relies on silicon as an electrical semiconductor will become useless. So if we get nuked, I'm gona crank up the music.. because I can!
> *



Haha, but not really.  You'll have to replace the switches, and your power supply as well as find a rather LARGE reliable source of power.  But really tubes are much more efficient, especially at high power.  They just have no life and are expensive to make.

But back to the subject.  Since the only thing I have is a Sony Clie with an MP3 player and the max memory stick is 128 MBytes, I've had to settle with 160Kbps.  A 10:06 song (Symphony No. 29 A-Major K#2) takes about 11855 KBytes and allows me to fit 13 songs (~8min/song) on there with about 10 MBytes left.  Of course the only thing I listen to them with are the Sony supplied headphones so I don't know how really good the songs actually do sound.  Kinda like my Mac, whenever somebody complains how slow OS X is I wouldn't know because I've never seen it run on anything faster....


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