On 30 Apr 2000, Stainless Steel Rat wrote:
> * las <[EMAIL PROTECTED]> on Sun, 30 Apr 2000
> | Compression as I understand it is an encoding and decoding process.
> | Anything that is compressed will have to be "decompressed" in order to
> | play it.
>
> CD-DA has this thing called a digital to analog converter for playback. So
> if analog to digital is compression then digital to analog is decompression.
But analog to digital conversion is not compression, so this is a moot
point.
> | Since if you cut the frequency response off at a certain point and can
> | never recover the sounds above that frequency response, that is not
> | compress. Compression allows you to recover a facsimile of the original
> | source. Just how different that is depends upon how lossy the technique
> | is.
>
> In what way is this facsimilie reproduction different from an audio CD
> compared to the original analog source? Because that is what you are
> getting out of the player: a facsimilie.
Is an audio cassette then a "compressed" format because it's physically
smaller than a record? Again, compression is something in the digital
domain.
> | But in the terms we think of it today (and the definition that I accept
> | (for what ever my opinion is worth) the term compression means encoding
> | and decoding.
>
> How is converting an analog signal to a digital data stream different from
> "encoding"? How is converting that digital signal back to analog not
> "decoding"?
Compresion is something that happens purely in the digital domain, by
definition.
> | MP3, ATRAC are compression techniques.
>
> Technically, ATRAC is not a traditional compression algorithm, but bitwise
> reduction. But we call it "compression" anyway because the end result is
> to make the data smaller. MP3 combines bitwise reduction and Huffman
> coding (a lossless compression scheme).
Please cite a source for your definition of compression that excludes
ATRAC?
"Data Compression Method: ATRAC"
-Sony, on the spec sheet for the MZ-R90.
http://www.sel.sony.com/SEL/consumer/ss5/car/mdwalkmanrtm/playerrecorder/mz-r90_specs.shtml
"The ATRAC (Adaptive Transform Acoustic Coding) data compression system
was therefor designed..."
-the paper produced by the designers of the ATRAC algorithm in 1992.
http://www.minidisc.org/aes_atrac.html
It would appear that you have developed a unique definition of compression
that includes some things and excludes others. If you are going to claim
ATRAC is not compression, please cite a source.
> | Cutting frequency or limiting the difference between the quietest and
> | loudest sound is not in my opinion what we think of today when we speak
> | about compress (although in the broadest sense removing or limiting
> | anything probably could be called compression-I just don't think it is in
> | common usage of the word today.
>
> But that is what ATRAC does, and we call it compression. So it is common
> usage even if most people do not relize it.
ATRAC does it by a different method; ATRAC compresses it to do this. If
you use an analog cutoff filter to cut off all sounds above 5kHz, you
haven't compressed the sound.
gopi.
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