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Old 07-27-2020, 11:34 PM   #1
TonyGlover
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Default Why does 44100Hz mean 44473Hz ?

I was curious if Reaper sent correctly the packages. That's how I did a test with DebugView.

Reaper sent 1,000 packets of 1024 samples in 23,025 seconds.

That means 44473Hz not 44100Hz.

Another aspect that I don't understand, the packets are sent at about 23 milliseconds even with the 8x1024 setting in the Reaper that seems to be ignored, I mean that 8x.

Can someone please clarify for me?
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Old 07-28-2020, 12:06 AM   #2
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I don't know, but you could do another test: Generate a sine wave at a known frequency, e.g. 440 Hz, and measure this frequency using an external tuner (e.g. a guitar tuner or a smartphone). If your setup is really running at 44473 instead of 44100 Hz, then your sine wave will be 15 cents too high.
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Old 07-28-2020, 10:05 AM   #3
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44.1 KHz does NOT equal 44100 Hz. It equals 44.1 x 1024, or 45,148 Hz. Since some bits are protocol/error detection, the actual data throughput will be a little lower. All seems OK to me.
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Old 07-29-2020, 12:26 AM   #4
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Quote:
Originally Posted by TheMaartian View Post
44.1 KHz does NOT equal 44100 Hz. It equals 44.1 x 1024, or 45,148 Hz. Since some bits are protocol/error detection, the actual data throughput will be a little lower. All seems OK to me.
Actually for Hz kilo means 1000 not 1024, so 44.1 kHz really is 44100 Hz.
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Old 07-29-2020, 12:39 AM   #5
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Heinrich Hertz obviously flunked computer class.
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Old 07-29-2020, 04:10 AM   #6
TonyGlover
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Quote:
Originally Posted by TheMaartian View Post
44.1 KHz does NOT equal 44100 Hz. It equals 44.1 x 1024, or 45,148 Hz. Since some bits are protocol/error detection, the actual data throughput will be a little lower. All seems OK to me.

You confuse kilobits with kilohertz...
1kb=1024b and 1kHz=1000Hz


Maybe that's what the sound card packages ask for.

What is the mystery of transforming these blocks of data from Host to sound card. Given that the sound card has its own settings: samplerate, sampleblock etc ... ?

In the example cames with IPlug I find a code which don't understand


Code:
    for (int i=0; i<nFrames; i++)
    {
      gBufIndex %= gSigVS;

      if (gBufIndex == 0)
      {
        double* inputs[2] = {inputBufferD + i, inputBufferD + inRightOffset + i};
        double* outputs[2] = {outputBufferD + i, outputBufferD + nFrames + i};

        gPluginInstance->LockMutexAndProcessDoubleReplacing(inputs, outputs, gSigVS);
      }

      // fade in
      if (gFadeMult < 1.)
      {
        gFadeMult += (1. / nFrames);
      }

      outputBufferD[i] *= gFadeMult;
      outputBufferD[i + nFrames] *= gFadeMult;

      outputBufferD[i] *= APP_MULT;
      outputBufferD[i + nFrames] *= APP_MULT;

      gBufIndex++;
    }
What does that gSigVS mean, shouldn't it be sampleblock or nFrames value?

Last edited by TonyGlover; 07-29-2020 at 10:34 AM.
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