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NO! NO! NO!

Sorry for yelling, but this is a common misconception. MP3 is LOSSY!! Think of a MP3 as a JPEG (in fact they are the exact same concept). When you compress a TIFF into a JPEG you are throwing out information. It is lost.... FOREVER! IT IS NOT A FIXED ALGORITHM!!! JPEGS and MP3s ARE NOT just equations that are reverseable. They THROW INFORMATION AWAY that the engineers who made JPEG and MP3 thought you could not see or hear. The JPEG does a pretty good job when you uncompress for viewing, or when you convert a JPEG back into a TIFF (like burning a MP3 back to redbook standard format).

BUT BUT BUT, if you look close you will see the TIFF that was coverted to JPEG and back to TIFF is NOT as high quality as the original TIFF because the information that was THROWN away was lost and cannot be recovered. HOWEVER you will notice that the file size of the original TIFF and the converted TIFF are the same! How can this be? The JPEG when you uncompress it GUESSES the missing information it threw away, and yes it DOES guess wrong. And if you recompress a JPEG over again, the quality drops even more, and if you were to recompress a MP3 it would lose even more quality, even if you use a higher bitrate!

MP3s work the EXACT same way. A MP3 will NEVER be as good as a CD because infomration is ALWAYS thrown away, never to be recovered.

I think people get confused because .ZIP files are compressed but when they are uncompressed they are EXACT copies of the original. They do not throw away any information at all... which if you think about it makes sense because if it threw ANYTHING away, the zipped file would no longer work at all! Photos and Music can be "fudged" and still look reasonable, and sound reasonable. But a txt document cannot be fudged or it will have spelling errors etc. that cannot be overlooked... or if it is a compressed program file it will not run any more... See what I am saying. MP3 and JPEG use the idea that MOST people will not be able to notice the difference. But in reality MOST people can if they try.

That said, for the amount of compressing mp3s and JPEGs to, they are amazing, and worth having. But the actual never been compressed TIFF or CD (AIFF or WAV) files are better!!!!! So again, convienince is nice, but you are not getting CD quality music. Close, but it is not no matter what you do with the files. I hope this is starting to make sense to people. No one in their right mind really thinks JPEG is as good as a TIFF or TGA!!! Why people think MP3s are as good as a CD is just beyond me! I can hear the difference from a mile away. The perfect place for MP3s is in the car because the road noise cancels all the quality anyway and no one can hear the difference. Or cheap stereos work fine with MP3s.

Regards,

Sean

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I just wanted to add, when you compress to a JPEG or a MP3 you can get, 1 to 4, 1 to 8, or even 1 to 16 compression ratios in filesize!!!!! (depending on quality setting) But with .zip you rarely even get 1 to 2 compression ratios!!!!! Why do you think that is?? Becuse .zip compression does not throw anything away. MP3 and JPEG DO! Throwing away information is BAD.

Regards,

Sean

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Tim,

Constant? When, if ever, did I ever before poke fun at you? Lighten up - your getting WAY too sensitive.

I don't believe I said "YOUR CONSTANT" I said "THIS CONSTANT" I did not intend to make it sound like it was constantly from you what I meant is that it has become a common practice to cop out with such statements when the going gets tough. Its childish and rude. I'm sure you did it in pure fun and I'm sorry you recieved the brunt of my frustration for what is really what others have done and currently do. Hope we can put it behind us !

Craig

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Sfogg

? Checksum how does one do this or what program will allow me to look at the actual file content. I am not one that takes anyones word for anything I have to see it for myself. I just did exact audio copy on the burned from MP3 to redbook track and a Original CD with the same track. File size is Identical. So how do I check what the file consist of ?

Craig

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Craig,

"Checksum how does one do this or what program will allow me to look at the actual file content"

You use a hex file comparison program:

For example:

http://www.fairdell.com/hexcmp/

http://www.mpi-hd.mpg.de/krae/Group/Cermak/Utilities/CmpHex.HTML

or literally dozens of others.

Or a hex editor:

http://www.hhdsoftware.com/hexeditor.html

and compare the two files yourself. The first line or two of the wave files will probably be the same (it is header info about the wave file) but once you get a little further in you will see plenty of places the data is different. IOW, it isn't a bit for bit copy.

When you run this stuff above do yourself a favor and use as small of a wave file as you can. A second or two of music will be more then enough. Doing a file compare of a couple of 30 meg files would get old very quickly.

" I just did exact audio copy on the burned from MP3 to redbook track and a Original CD with the same track. File size is Identical. "

Like I said above that is because the playing time is identical. For a given amount of playing time in a wave file the size of the data (no matter what the actual music is) will *always* be the same. That is because it is a fixed format. One sample of a single channel of CD audio has 16 bits. Those 16 bits are where the audio is encoded.... but not matter what you encode it is still 16 bits.

File size is irrelevant for the data content.

Shawn

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Craig,

Wordpad isn't really built to open those size files and it is going to display the data really poorly. It will try to show the hex data as ASCII text so it is going to look really funky.

A real hex editor will show the data as hex directly and should also show you which byte you are on so you can be sure you are comparing byte for byte.

The hex file compare programs should automatically show which bytes are different between the two files.

Shawn

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Craig and others...

If your just trying to validate that the data written back to CD will not equal the original, just rip some CD tracks to computer using a much lower than normal bit rate, then using iTunes burn a CD with those tracks. Try setting a custom bit rate of about 64 kbps or lower. If you burn a CD with those compressed files it will be very very evident of the quality loss.

I would feed better if Craig stayed away from hexadecimal editors being that he admittely is not a computer geek.

- tb

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Tim

To late I have already done the hexadecimal and I may not be computer programming proficient but trust me I know windows like the back of my hand. I built PC's and loaded windows on 100's. Not a programmer but very handy if I have to be. My existing main PC has had 3 different motherboards installed over the last three years without reloading windows ! I got out of the PC building and repair hobby simply because there was no profit to be had and to many headaches from people that have no clue how to use a PC responsibly. I feel for anyone working for the likes of Dell or Gateway in there tech support !!

Okay this is what I found. You both are correct and the file is not Identical. But there is something funny here. I would think if the information is discarded then zero's would be installed in there place just to take up the space. The files for the most part are very similar but the values are different. Also what really is strange is the file originating from a MP3 that started life out at 224 bit is longer and has MORE information on it that the file from the original CD. I still say people are making assumptions that are not all together true here. If the MP3 compression can determine what is not supposedly noticeable to the human ear and discard then the decompression must be replacing it with something other then just blank space nothingness !

I played these files back and forth for my 16 year old daughter and she swears they a dead nuts Identical !!

The Fairdel Hexcmp program sure made comparing simple !! Thanks

Craig

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yes it does have to fill the space of where it threw away information with something... like I said.. it GUESSES the information. But they are just guesses... have you heard the "breathing" of the noise in a low bitrate MP3? Or the weird "warble" in sounds like a piano or flute? This is information ADDED by the algorithms that are extra information, but not accurate. I don't know if you are familiar with animation but keyframing is similar to what MP3 does. It looks for the most noticable things in the music and "keyframes" that info, and throws away everything else.. then when it decompresses it has to guess what is between those keyframes by interpolation. Usually it does pretty good, but it also will make mistakes... and some parts that it THINKS a person could not hear, it just throws away entirely and does not even try to reconstruct it. For example sound waves of other sounds going on during a drum hit will be dropped because most people could not hear them over the impact of the drum sound. Those other sounds are just thrown away. Those sounds are recorded... it is just our brain that cannot process all those sounds. Some people CAN hear those sounds though. The MP3 format is carefully constructed to take advantage that most people can not hear certain characteristics of sound waves. But it makes a lot of assumptions that many people can hear. Just trust us that know... once a file is compressed into MP3, you can NEVER EVER EVER reconstruct it exactly.

Regards,

Sean

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So I guess I was on the right track assuming that the discarded material was not just filled in with nothing to take the space. Although my beliefs before we started this thread were definitly wrong. I myself do not rely on CD's as my serious listening format so I can live with what seems to be not descernable sound loss for the convience of downloading and burning. Especially when were mostly talking Rock music here. I myself don't hear a difference that I can put a handle on and also my Daughter has the same impression. I also wonder if this new format from Apple MP4 ? does a better job then MP3 which would render the difference even harder to hear ?

Craig

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Yep, that is the beauty of MP3. They are a wonderful format. And it is getting better all the time... most of the quality differences are on the encoding side, not the decoding. So as encoders get better the format gets better. I think the best encoder out there, is any of them that use the LAME encoder. At 256kbits/sec it is hard for me to hear any difference. Only with headphones, usually, can I hear any difference. Sometimes there will be some obvious flaw... The only thing that really bothers me consitently is the loss of dynamics many times.

I have a server that I am encoding all my CDs onto so I can listen to them anywhere in the house. I have a 200 gig HD and it is almost full hehe!! It might sound from my posts that I do not like MP3... far from it. It is wonderful, and so is JPEG. But it is not as good as CDs.

But, I don't think I would buy an album only in MP3. I prefer to buy the CD and rip it myself. That way I am assured highest quality MP3s when I rip them (because the bitrate and encoder that Apple uses on their MP3s I can hear the difference, and it bothers me, but on the ones I rip at a higher bitrate and the LAME encoder I have a harder time hearing things that bother me), and I get the absolute best quality with the CD. Also, I do not want the CD format to die off in favor of MP3. That would be a huge step backwards!

Regards,

Sean

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Craig,

The files should look very similar. In a redbook PCM data stream there is a preamble for each and every frame as well as info saying if the frame is for the left or right channel then the data itself. That info will probably be identical between the files and it will happen very very often.

"I would think if the information is discarded then zero's would be installed in there place just to take up the space."

Not really it doesn't work that. If it put in nothing but zeros you would have dead spots in the sound.

What it throws away is parts of the music it 'thinks' you can't hear. That may be info that is lower down in the noise floor, or material on the very high end or other things. So its removal doesn't really result in all zeros, just a different waveform. They also tend to reduce the S/N ratio of some parts of the music such that in the compressed file itself it takes less the 16bits to store the waveform and increase the noise in the music. Also some (like DD) will store material that is duplicated in more then one channel (bass tends to be strongly correlated in multiple channels) just once (which saves space) with instructions to duplicate it in the appropriate channels on playback.

The process is obviously very involved but as you have now seen for yourself the compression/decompression isn't bit for bit identical to the source.

"Also what really is strange is the file originating from a MP3 that started life out at 224 bit is longer and has MORE information on it that the file from the original CD."

That might just be some difference in the header info or if the original wave file wasn't really a complete frame the encoding/decoding might make it 'to spec.'

"I played these files back and forth for my 16 year old daughter and she swears they a dead nuts Identical !!"

They can work very well at high bit rates. Some material is harder to compress then others so as you try different type of music you may find some that are more obviously different then others. I have a CD with a test tone that is brutal for encoders. Also if you listen in any form of surround sound (Logic 7 and PLII for example) it is easier to tell problems as phase relations aren't as well defined in the compression.

For my MP3 jukebox I encode everything at 320kbps using LAME and the quality is very good.

"The Fairdel Hexcmp program sure made comparing simple !!"

Yup, that is what they are meant for.

Shawn

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Apple would very much like to steer many more users into downloadable music, it will be interesting to see the result on CD sales in a few years. iTunes pays the record companies an average of 65 cents for each track it sells, plans are for the 400,000 tracks available in October to eventually grow into millions offered.

The flip side to the convenience is a copy-protection scheme, though you can burn individual songs onto an unlimited number of CDs, the iTunes jukebox software will allow a specific playlist of songs or an album to be burned onto a CD ten times (you can burn more than that only if you manually change the order of the songs in the playlist). Each song is encrypted with a digital key so that it can be played only on three authorized computers, which prevents songs from being transferred online. And if you burn the AAC songs onto a CD that a conventional CD player can read and then re-rip them back into standard MP3 files, the sound quality is reportedly awful.

There's an online AAC knowledge base, as well as a forum dedicated to audio compression for additional info. Nice to see they have some time for an audio hardware forum, too.

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Guess what DLL I use to ripp CD's !! Yup Lame DLL I use CD & Go suite and it allow you to choose between like 20 different DLL files I tried them all and settled on LAME as the best sounding. I settled on 224 for the bit rate. I can't say I have 200 Gig though !!

So the Apple program allows you to choose higher bit rates when ripping do you think using it with higher bit rates will exceed MP3's Quality bit rate for bit rate ?

Craig

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And if you burn the AAC songs onto a CD that a conventional CD player can read and then re-rip them back into standard MP3 files, the sound quality is reportedly awful.

Sorry just did it and it sounds Identical when ripped to MPS from a CD purchased and burned from Apple.

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Sorry just did it and it sounds Identical when ripped to MPS from a CD purchased and burned from Apple.

Interesting, that wasn't Apple's hopes anyway, chalk 1 for the pirates. Still studying the AAC flavors (iTunes uses LC) as well as the bit rate debate, appears in the end you may have to trust your own ears.

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