Before I begin: anything that really ever doubts MD is less than what the
research papers say it is gets lots of flame on here. But anyway.
Supposedly, louder sounds "eclipse" much of the quiet sounds, so the data of
those quiet sounds can be omitted. Psycho-acoustics also takes the
sensitivity of the ears into consideration. The two together would seem
like a lot of "savings".
Some of the supposed "advancements" commercialized by the companies:
Sharp ATRAC 6 - mostly same as 5, but the encoding algorithm is variable
according to time, frequency, and loudness (not sure if it's loudness).
Sony Type-R - double computation power, supposedly leading to better
realization of the algorithm;
Matsushita H.D.E.S. - Emphasis on low and high frequencies, which in a way
goes against the original ATRAC principles. Adapts to cut down pre-echo
noise (noise that may occur when level suddenly goes up).
Pioneer ARTIST-SYSTEM - DSP creates masking database on the spot and sends
it to ATRAC to determine what will be encoded.
All these newer ATRAC algorithms seem to have been designed, so that the
highest frequency band (15-22kHz) is represented as much as possible (Sony
4.5 was improving from 4 in this aspect). Traditionally, since the ear isn't
that sensitive to these frequencies, this is one of the least emphasized
band for encoding. Yet maybe it's true that more-than-natural emphasis on
low and high frequencies would sound more pleasant to the ear?
It seems that other key to good encoding is speedy computing. The article
about Sony version 3.5 on MDCP had the developers mention something about
that, I think it's about the 3.5 chips being able to do floating-point
calculations. There's definitely this factor in Sony going from 4.5 to
type-R.
>From what little knowledge I have, it seems that ATRAC is more than capable
of representing all genres of music with ease. But maybe ultimately moving
just slightly away from the basic principles give more pleasant results.
Just maybe.
Leon
> I know that I wrote OT, but there is an On Topic
> (OT?) :) reference as well. Minidisk recorders and the ATRAC compression
> system eliminate a large portion of the audio from a signal, and we have
> all been told that this missing signal not in the human hearing
> spectrum. Now many of these special areas of sound are in the extreme
> ranges of frequency, and I can't imagine that the ATRAC and other
> compressions do not remove/alter the effect of many types of
> music. Thoughts?
>
> Asking a question, and possibly throwing a spark in for good
> measure,
>
> -=James
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