Dan Dugan wrote:
> Raimund Specht, you posted:
>
>
>>Walt, I have just prepared a quick comparison of both uncompressed
>>and compressed digital audio as you suggested:
>>
>>http://www.avisoft-saslab.com/compression/compression.htm
>
>
> Thank you, Raimund, this is a very nice illustration of what's going
> on in a typical good psychoacoustic data reduction scheme. Could you
> add the color/level scale to your spectrogram illustrations?
>
>
>>I guess, that you will argue, that these tests were made with MP3
>>and not with the latest ATRAC system.
>
>
> You're using a similar data compression ratio, and MP3 is designed
> with similar principles to ATRAC, so I thank you for composing a very
> helpful educational page. If I were to ATRAC process and unprocess
> your test file, without analog conversions, would you be willing to
> plot and post those results too?
>
>
>>However, I will NOT buy one of
>>these expensive MiniDisk machines. The underlaying principles are
>>always the same. The improvements may lead to better listening
>>pleasure, but the loss of data will remain.
>
>
> What compromises you accept in exchange for economy and portability
> are always up for discussion, and ultimately a personal choice. I get
> fabulous, publishable recordings of both music and nature on a cheap
> Sharp portable MD! I agree with Walt that the degradations of "lossy
> compression" recording are almost always insignificant for both
> personal and scientific uses, and your excellent analysis of MP3
> doesn't change that opinion. Thank you for making the discussion more
> objective.
Before you get too objective, look at the original wave file on a wave
by wave level. Just how often will we find such a waveform in natural sound?
Next, examine exactly the gain used on the mp3 and original. This has a
very strong bearing on the resulting display.
It's a test of how well mp3 handles sharp high frequency transients,
waveforms that closely resemble clipping artifacts and so on. Looks a
lot like a square wave generator was used to generate a lot of the
original. To assume this bears any resemblance to natural sound is
interesting in what it tells about people.
Try how well a DAT does on this while you are at it. Or a hard disk
recorder. Or a D/A.
Walt
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