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Re: Itunes, bitrate, and other questions...
CV #284320 12/29/09 06:08 PM
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Wouldn't that be the ultimate irony. But nope. I don't like his posts, they hurt my head.


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Re: Itunes, bitrate, and other questions...
ClubNeon #284335 12/29/09 07:02 PM
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 Originally Posted By: ClubNeon
With lossy encoding, what you're saying can sort of happen. MPEG audio uses a cosine transform. It basically takes the time-domain sample rate, and converts it into frequency domain. It than can analyze that frequency information, and try to find slices of a cosine wave which fit the original wave form. This Fourier transform in theory can be lossless, but it would take an infinite number of slices to completely reproduce an original analog signal.

Luckily CD audio has only 44,100 samples a second (time domain), and when converted into the frequency domain the highest frequency which can be reproduced is 22.05 kHz (Nyquist limit). So using 22k cosine slices for every second of audio would be able losslessly recreate the original PCM (within some very small margin of error). In practice that's a worse case, and one can get by with many less pieces and still have near lossless encoding.

But the problem is storing that many cosine coefficients would take more room than the original 2-byte (16-bit) samples. So in order to get the 10:1 compression which is common from MP3s, even fewer slices are used. This only gives a rough approximation of the original waveform. Fine details (like high frequency information) gets smeared together, and large rapid changes cause pre-echos or ringing.

None of this applies to truly lossless encoding schemes. They may use some perceptual estimation routine (DTS does this, Dolby's MLP along with FLAC use strictly numeric prediction) for the initial data reduction. But it goes one step further, and then checks this estimation, and looks back at the original recorded value. If there is any difference that's stored too. So as the final decode is done by the player/receiver it comes up with the estimated value, and then applies any correction to get the exact original data back. There's no loss or error.

Now this is starting to sound alot more like the conversation the other night though there was alot more talk about hexadecimal coding and compression by data prediction and algorithmic math.

As Ken says, and it does seem rather obvious when you take a step back, the data on a cd is already in bit digital format so it seems easy to reproduce that original code again with error checking after decompression.

Where the hell were you boys the other night when this conversation was happening? Over 7 bottles of various French red and white wines eh??!!!


"Those who preach the myths of audio are ignorant of truth."
Re: Itunes, bitrate, and other questions...
chesseroo #284363 12/29/09 11:07 PM
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I... don't know. I'm sorry I missed it.


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Re: Itunes, bitrate, and other questions...
Ken.C #284375 12/30/09 12:55 AM
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 Originally Posted By: kcarlile
I... don't know. I'm sorry I missed it.

Hmm, possibly because i think it was Christmas night.
Possibly...


"Those who preach the myths of audio are ignorant of truth."
Re: Itunes, bitrate, and other questions...
chesseroo #284392 12/30/09 03:51 AM
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They mostly come out at night. Mostly.

Re: Itunes, bitrate, and other questions...
CV #284395 12/30/09 03:54 AM
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Sounds like my wife might get me a new IPOD Classic 160GB. \:\) With that in mind I will probably rip my CD's to an external storage device using Apple Lossless, and then follow Eric's instructions to create smaller AAC files for the IPOD.

I am curious what others are doing.


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Re: Itunes, bitrate, and other questions...
chesseroo #284397 12/30/09 04:00 AM
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I went through this agony a year ago. Or maybe it was two years….. 900 CD’s ripped. It was a slow and painful process. If you are going to rip your collection, you might as well do it right the first time, get them on your hard drive, then you can screw them up at your leisure. Just make sure you keep the original rips somewhere that you can keep the folder unadulterated.

I would highly recommend you rip them to FLAC first. After trying several different programs, I sure wish I would have just used DB Poweramp first. It will rip to two different bit rates and dump them into two separate folders at the same time. You can set it up however you wish. Warning: be sure you have your options set up for tagging as you want them to be recognized the way YOU want them filed and not the software defaults first. If you don’t, you will forever be trying to fix them. Another plus for DBPoweramp is that it will grab album art as you rip. Many don’t, and it’s very, very difficult to find artwork after the fact unless you enjoy more pain to find each album one at a time. I’ve tried several batch gathering tools to find the art work, and none work. iTunes does, but it won’t share them with other programs……

So after you get them ripped, I would do as I did. Buy an HP smart media server and store all your music files on it. They are cheap now. I installed Squeeze Box onto the server and I use the Squeeze Box Duet to talk to my home stereo. I listen to the FLAC rips with the SB.

For my iPod, I have the 320K ripped songs that are in a separate folder. I point iTunes to that folder.

iTunes does not like to play with other programs, so you will always be wondering just what in the heck happened for one reason or another.

If you are interested in doing this, just let me know and I’ll go into more detail.

Re: Itunes, bitrate, and other questions...
michael_d #284399 12/30/09 04:14 AM
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Thanks Mike...


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Re: Itunes, bitrate, and other questions...
SirQuack #284404 12/30/09 05:06 AM
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If it was a 160GB, I'd probably rip it as ALAC and just use that on the iPod. That's over 400 albums worth in lossless--how much music do you need with you at any given time?


I am the Doctor, and THIS... is my SPOON!
Re: Itunes, bitrate, and other questions...
Ken.C #284408 12/30/09 05:20 AM
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Yeah, I can't imagine wanting to take my whole collection with me in a portable device, unless I become a hobo.

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