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Groups > comp.sys.apple2.programmer > #4516

Re: WAV file playback

Newsgroups comp.sys.apple2.programmer
Subject Re: WAV file playback
From Michael J. Mahon <mjmahon@aol.com>
References <3940d945-abbb-4cc8-9057-67b37c879c01@googlegroups.com> <a83efba1-a341-4589-bd91-2617663f835f@googlegroups.com> <Uf-dncBDSKQrrEHHnZ2dnUU7-fPNnZ2d@giganews.com> <7f7800cc-9d9a-4402-8540-2494e10138ea@googlegroups.com>
Message-ID <Y_2dnTyImMMriEPHnZ2dnUU7-RXNnZ2d@giganews.com> (permalink)
Date 2018-04-23 12:19 -0500

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Michael Pohoreski <michael.pohoreski@gmail.com> wrote:
> On Saturday, April 21, 2018 at 11:54:51 PM UTC-7, mjm...@aol.com wrote:
>> rate cannot alternate between 92 and 93 cycles, since the jitter would
>> introduce spurious frequencies surrounding 5.5125 KHz. 
> 
> Is this 5512.5 Hz derived from 92.5 cycles?
> 
> Hmm, I'm using the formula: 
> 
>   Hz = 17,030 * 29.97 / cycles.
>      = 510,389.1 / 92.5 
>      = 5517.72 Hz.
> 
> Or are you using a NTSC rate of 29.94 Hz for the formula?
> 
>    Hz = 509,906.25 / cycles
>       = 17,030 * 29.94 / cycles
> 
> It doesn't look like 29.9695 for NTSC's field rate is the correct Hz?
> 
>    Hz = 17,030 * 29.9695 / 92.5
>       = 510,380.585 / 92.5
>       = 5517.62 Hz
> 
> 
> 

Much simpler. ;-)

5.5125 KHz is derived from the (somewhat) standard 11.025 KHz audio
sampling frequency, which is 1/4 of the standard 44.1 KHz CD sampling
rate—what Apple once referred to a AM radio quality. 

So the highest frequency that can be transmitted by a stream of 11.025 KHz
samples is the Nyquist frequency: half the sample rate. Any higher
frequencies would be aliased to lower frequencies. 

I was simply observing that the noise introduced by playing uniformly
sampled signals at a non-uniform playback rate will be aliased back into
the audible range, and therefore non-uniform playback rates should be
avoided if possible. 

A uniform sample playback rate which is about 0.5% fast is generally
imperceptible (except for those unfortunate folks with perfect pitch). 

-- 
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

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Thread

WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-19 12:15 -0700
  Re: WAV file playback Chris Vavruska <vavruska@gmail.com> - 2018-03-19 18:28 -0700
    Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-19 19:43 -0700
      Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-20 01:55 -0500
        Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-20 14:49 -0700
          Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-21 00:23 -0500
            Re: WAV file playback Tom Porter <laseractiveguy@gmail.com> - 2018-03-21 07:36 -0700
              Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-21 10:13 -0500
                Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-22 22:27 -0700
                Re: WAV file playback James Davis <JPD.Enterprises@outlook.com> - 2018-03-24 12:35 -0700
                Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 19:44 -0700
                Re: WAV file playback James Davis <JPD.Enterprises@outlook.com> - 2018-03-25 09:22 -0700
                Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-25 10:08 -0700
  Re: WAV file playback Tom Porter <laseractiveguy@gmail.com> - 2018-03-24 06:05 -0700
    Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 11:50 -0700
      Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-24 20:18 -0500
        Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 19:29 -0700
          Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-24 21:53 -0500
            Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 21:49 -0700
              Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 22:25 -0700
                Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-25 09:44 -0500
          Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-24 22:43 -0500
            Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 21:43 -0700
              Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-03-25 09:42 -0500
    Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-03-24 11:56 -0700
  WAV file playback Michael Pohoreski <michael.pohoreski@gmail.com> - 2018-04-21 21:01 -0700
    Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-04-22 01:54 -0500
      Re: WAV file playback Michael Pohoreski <michael.pohoreski@gmail.com> - 2018-04-22 22:33 -0700
        Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-04-23 12:19 -0500
      Re: WAV file playback Michael Pohoreski <michael.pohoreski@gmail.com> - 2018-04-22 22:53 -0700
        Re: WAV file playback "Frank M." <frank_o_rama@hotmail.com> - 2018-04-23 08:42 -0700
        Re: WAV file playback Michael J. Mahon <mjmahon@aol.com> - 2018-04-23 12:19 -0500
          Re: WAV file playback Michael Pohoreski <michael.pohoreski@gmail.com> - 2018-04-23 22:38 -0700

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