Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!hubcap!ncrcae!ncr-sd!crash!pnet01!haitex
From: haitex@pnet01.cts.com (Wade Bickel)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Is 29 Khz really the fastest audio playback rate? (New Agnus)
Message-ID: <2979@crash.cts.com>
Date: 18 May 88 09:36:30 GMT
Sender: news@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 51


        First of all,  ANYONE WHO HAS NOT THOUROUGLY INVESTIGATED THE 
      NATURE OF SOMEONE ELSE'S REQUEST FOR INFORMATION HAS ABSOLUTLY NO
      BUISNESS CLAIMING THAT SUCH A PERSONS' REQUEST IS UNFOUNDED. THIS
      WAS MADE PAINFULLY CLEAR IN THIS THREAD WHEN ONE PERSON WHO DID NOT
      EVEN UNDERSTAND THAT IN ORDER TO SAMPLE A WAVEFORM OF A GIVEN
      FREQUENCY THE SAMPLES *MUST* BE TAKEN AT TWICE THAT FREQENCY.
      FAILURE TO DO SO RESULTS IN GROSS ALIASING WHICH IS QUITE NOTICEABLE
      AT SAMPLING RATES BELOW ABOUT 40KHZ.

        THIS IS A PLACE TO OFFER POSITIVE SUGGESTIONS OR CRITICISMS.

                ===== BREIF FLAME OFF =====

        Also, I happen to have started the laborious task of reading my
      DevCon notes last night, and just happend to run accross the
      following:

        (found in section 1, actuall page 16, titledt a the bottom
         "Outline of Features in V1.3, V1.4 and the Enhanced Custom Chips"
                               "Page 3"

           Agnus

           1).....

           Audio Channel period: The minimum period is 124 color clocks,
             which gives a maximum sample frequency of 28.86 khz. However,
             if the horizontal frequency is different, the sampling freq.
             can be higher.  The minimum period is (Htotal+21)/2 color
             clocks.
                                                                          )

  
          Of course this may not apply to current rev.s of Agnus, but it
        might???  If it is possible to alter the horizontal freq. then this
        might be a way to achieve a higher sampling rate, at the expense of
        the display (???).

          Hope this is usefull to someone.


                                                        Thanks,


                                                                Wade.


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