Born Dead #02 04 ноября 1998

Звук     AY/YM     Программирование

new world of sounds - High-quality digital audio AY - dream or reality.

                   NEW IN THE WORLD OF SOUNDS AY - 2


(C) MONSTER / SAGE GROUP

                                  High-quality digital sound

                                  on ordinary AY -

                                   - Dream or reality?


    Continue our discussion of quadrupeds Moscow spektrumista 
Oldman'a titled "UltraSound4x3 metod for AY chips". 


  After careful examination of the theoretical and practical 
results by Dmitry Grigoryev revealed the real reasons low 
efficiency of the method. 

  The first and most fatal - simultaneity O ports
AY sample sampling, which is an insurmountable challenge. In
Finally, we hear while playing is not only synthesized by the 
three channels of higher quality signal, but each channel 
separately, which is nothing but noise! And as I have mentioned 
in the previous issue of the newspaper, I was able to reduce 
the time between records in the AY data ports, but 
unfortunately the noise level was unchanged.


  Second, and most harmless in this method poser - Medium
sound channel in the AY (I've got it "B", some "C" because of 
the different connection schemes) is reproduced at 30% quieter 
than the extreme channels. (In my card from Cervus Elaphus 
Company (Moskow) from AY, such as most common in the years of 
prosperity Speccy, Channels smiksovany that way.)


  Noise is inevitable in the method and the third reason. When 
listening digitizing the stereo equipment extreme sound 
channels "A" and "C" sound separately, and obtain an output 
signal, which is the sum three channels, not really!


  The result of all my arguments, as well as learning more buggy
Dennis Sotchenko method (which except for the digitization of 
high frequency, we hear the whistle with an amplitude directly 
proportional to change in accordance with the deviation from 
the real values ​​of the sample) is the new method is very high 
quality playback of digital audio, entitled: 

 Middle Channel Correction (MCC) (C) 1998 Monster / Sage Group

Main advantages and features of MCC:

    - An almost complete absence of noise and distortion 
compared to 

      synthesis of single-channel linear 8bit'nogo sound.

    - Complete absence of high-frequency whistle.

    - Synthesis of 99 shades of digitization of the 256 
possible. 

A general description of the MCC method:

    - A basis the standard formula preorazovaniya 8bit'no
      second signal in 4bit'ny.

      LET AY = (LN (V +1) / LN 2) * 2-1: IF AY <0 THEN LET AY = 
0 

      AY (0 .. 15); V (0 .. 255)

      In my opinion the most correct. In this regard, I fully

      solidarity with Oldman'om.

    - In the channels "A" and "C" (extreme), or only in "A" or

      only in the "C", reproduced in the transformed higher at

      piped formula (corrected) 8bit'naya digitization
      ka. On average, channel "B" is reproduced Adjustment

      signal, reducing the deviation of output from the original
      tional, pre-a calculated for each gradation 8bit '

      Nogo signal.


  Wash easily and can not be, and higher-quality playback for 
4bit'nogo muses. coprocessor. True, there are several minor 
restrictions in the MCC. Correction signal must be played only 
on the average channel AY (for the minimum noise level), so any 
software that uses this method should ask the user which 
channel is in his Speccy medium (such as order: ABC or ACB?) 
Average channel should be smiksovan with the extreme in this 
regard: A and C = 100% B = 72% (again, for a minimum level of 
noise). Otherwise, you can score on these restrictions, or, if 
still not broke, re-calculate the table transformation for a 
specific scheme mixing channels. 

  For comments and questions related to
theory MCC method, write to the newspaper (address on last 
page). 

  This method is completely frivaren, but preferably in a 
software product that uses this method, we mentioned his name 
(MCC) and its author (Monster / Sage Group). 

  At lamer this request does not apply.
MCC are looking for all the sources in Fido, and on pages I-Net.


               To demonstrate the capabilities METHOD

             KEEP THE "SPACE" at boot time NEWSPAPERS

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                     Authors in this issue:
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                      ___
MONSTER / / SAGE GROUP - all codes, some text
MMCM ___ / / SAGE GROUP - music, logo
MARKET SOFT \ \ / / SAGE GROUP - intro gfx, correction
UnBEL! EVER \ \ / / EXTREME - all texts, main idea

              \ \ /

               \ __ \ / RuleZ Forever!!!

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                      Contact addresses:
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Post: 443074 A / H 9966 Muchkaevu Maxim Alekseevich (UnBEL! 
EVER) Phone: (8462) 941-595 Sergei (MMCM)

Telegraph: speed_co@yahoo.com

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