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Here are some approximate numbers to compare.

CD = 44100Hz x 16bps x 2 channels = 1411 kbps
MP3 = 44100Hz x 3.6bps x 2 channels = 320 kbps

Note the 3.6 bits per sample for MP3. Which is an approximation after compression.
 

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57 said:
I use Apple iTunes and it has a lossless encoder. Saves about 50%.
I should have been more accurate.

What I meant to say is that there is no generic means of compressing data losslessly to 2:1 (a la the WINZIP example). Now for a specific context of data (say audio files) you could come up with an encoding scheme that might achieve a better compression ratio, because the data has a fixed context and tends to be more predictable. You mention the iTunes encoder. There is also the FLAC encoder which is actually free.

There is a good comparison of lossless encoders here:
http://flac.sourceforge.net/comparison.html

You will see that even these encoders average >50% (except one) although they are all less than 60%. But look at the numbers for specific songs and you can see significant various based on the type of music. For some songs the ratio rises to 60+% whereas for some other songs the ratio drops to as low as 30+%. In fact, from the looks of it, it seems that classical music compresses better than pop music?
 

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ok so if you take a 320 kbit file and play it on a DVDA player as I have is my player down sampling it to 44.1

I've noticed sometimes my DVDA player does this as my player will read 44.1 ?

But isn't a DVDA suppose to play at a higher frequency? .... (im just learning about my player as you can tell)
 

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stampeder said:
Thanks for that! Does anyone know if MP3s can do multi-channel too, such as on an SACD?
That would be DD (Dolby Digital). The software cost alone would prohibit it.
 

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Just to clarify Filper's remark. MP3s CANNOT contain more than 2 channels. It is not in the spec. I believe WMA can contain more than 2 channels. Though I have never heard one. Not sure about AAC, but I would think it would.
 

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GQUEUE

I was using the WinZip as an example of lossless compression. I was not impling that we could use it on WAV files to save space!

As you have said, usng the proper encoder can save 50% without any loss of the digital signal ie APE, FLAC, WMA, etc

Anyone who wants to transfer their CD collection to MP3 (or whatever) should take one or 2 titles, rip them using various bit rates and sit down and decide which is the best for them. I did that and settled on the 320 VBR using the lame decoder. I think "most" people would be happy with that.
 

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A website I'd recommend on this subject is www.hydrogenaudio.org. I've been reading this site for years. A thorough comparison of lossless audio encoders can be found here http://wiki.hydrogenaudio.org/index.php?title=Lossless_comparison.

There's also an excellent audio format guide http://wiki.hydrogenaudio.org/index.php?title=Audio_format_guide where (lol) the first section is titled "Why no simple answer?". They cover many of the considerations folks have brought up and provide a framework for making choices.

On a side note, for anyone looking to digitize their CD collection my only advice (and the best decision I personally made) would be to keep a lossless rip of your CDs... it's worth the hard drive space. As codecs improve and change you'll thank yourself as re-encoding is far easier if you've got the lossless files and don't have to feed your CDs through your PC - again!!
 
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