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ATRAC vs. MP3 decoding/decompression question

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I'm having a hard time finding an answer for this: It seems to me that MD ATRAC1 files don't actually get uncompressed for playback, as they already contain all the data they will ever have. So, they don't have to be uncompressed dynamically for playback. Is that true? How about MP3 (et al.) then? Same as MD or is there a different process used for playback?

To give another example, just so I'm being clear, FLAC and ALAC files, while compressed, do contain 100% of their original data; thus, it seems to me that such files are uncompressed/decoded dynamically for playback.

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My understanding is that it is rather decoding than "uncompressing", when it comes to playback. And it is done by the codec of the given format. When "compressing" and audio file, it is actually encoding it (again, by that codec), and in case of certain formats this encoding can reduce the actual file size compared to the original wav audio - either lossy or lossless way, depending on the format. FLAC encoding is lossless, mp3 and ATRAC are lossy.

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the  compression only applies to reducing the size of the  resulting file, where  datas is THROWN AWAY - its not a  zip/unzip  idea. Atrac codecs  used various  psycho-acoustic facts  like if 2 sounds are of the  same frequency with one quieter than the other , you wont hear the quiet one so can be discarded without impairing the sound  you hear- maybe a Martian  could hear the  difference but Humans cant

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7 minutes ago, freddyjollo said:

the  compression only applies to reducing the size of the  resulting file, where  datas is THROWN AWAY - its not a  zip/unzip  idea.

Well, in the case of FLAC, it is very close to the zip/unzip idea. WAV is "compressed" to FLAC without throwing away any data, and the exact same WAV can be restored. The FLAC file is resonably smaller, than the original WAV file.

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yes  was talking about  normal Atrac - I know there are other more modern systems  that  remove  redundant data that can easily be replaced  on listening - similar ideas no doubt to how  hard discs can be compressed.  the op seemed puzzled at  why  atrac  dont need uncompressing and  presumably  "superior" to eg Flac

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8 minutes ago, freddyjollo said:

the op seemed puzzled at  why  atrac  dont need uncompressing

Because ATRAC is not compressed. It is encoded.

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14 minutes ago, freddyjollo said:

why  atrac  dont need uncompressing and  presumably  "superior" to eg Flac

We cannot really compare ATRAC and FLAC, a lossy and a lossless format. "Superiority" of ATRAC shows only on the playback side (like 20 bit oversampling etc.), while FLAC "simply" plays back the original audio - but preserves every single bit of it during encoding.

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I dont  know why you are taking issue  with what I say as  I am not saying  any of the above which u are taking out of context and misreading

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1 minute ago, freddyjollo said:

I dont  know why you are taking issue  with what I say as  I am not saying  any of the above which u are taking out of context and misreading

Am I? 

I am very sorry, if you misunderstood what I wrote. Where did I take anything out of context and misread?

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Let me as the OP just hop in for a second, if you would. I completely understand that ATRAC files are decoded, not uncompressed, for playback. There is really nothing left to uncompress. So I wanted to know if MP3 also works that way.

As for ALAC/FLAC, these files are assuredly compressed to begin with; then they have to be decoded for uncompression. So I think, anyway.

The reason I thought of any of this at all was that while listening to my JA22ES, I thought it sounded really good. And I wondered if, since an ATRAC file does not need uncompression, that might be a kind of processing benefit (like one less step). Wondered, too, if MP3s are similar to ATRAC files in that way, or not. I really didn't mean to start anything contentious though!

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well  one question since  Atrac is a discarding codec rather than an zip/unzip one are the resultant   files  actually decoded on playback unless they are encrypted?

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one can compare Atrac with mp3 as they work very similar.

The decoding is less besides the encoding takes it to the limit. If im not completely wrong the decoding is the same for flac as the compression only takes place when the file gets created.

 

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The major difference between ATRAC and MP3 is, if I recall the explanation correctly. one is in the time domain and one in the frequency domain. As well, later versions (ATRAC3/+) take special care with encoding certain recurring frequencies (ie steady notes) in the output by subtracting them out and encoding separately, thereby leaving more bits for the rest of the sound to be encoded (this means for example that pipe organs sound surprisingly good at low bit rates). ATRAC uses fixed frames covering a certain amount of time (i don't recall). All this stuff can be found on minidisc.org.

Stephen

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Thanks one and all. I finally found the right article to read about MP3 and I now understand that, as far as decoding/uncompression, MP3 and ATRAC are more similar than different. Neither is truly compressed in the same sense as a compressed, non-lossy data file. In any case, I intend to go on listening to MD and to avoid MP3 when possible, at least in the realm of lossiness. Pretty happy with ALAC, too, although to my ears, the best digitally sourced sound is still to be had from CD. (Maybe I like my CDP-XA20ES and its bass-heavy DAC a bit too much!)

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