FFT library taken from Audacity and ported to Pascal.

This will be used for the GetFFTData-Function of the Audio-Playback.


git-svn-id: svn://svn.code.sf.net/p/ultrastardx/svn/trunk@873 b956fd51-792f-4845-bead-9b4dfca2ff2c

1 files changed, 345 insertions, 0 deletions

diff --git a/Game/Code/lib/fft/UFFT.pas b/Game/Code/lib/fft/UFFT.pas
new file mode 100644
index 00000000..e97812f6
--- /dev/null
+++ b/Game/Code/lib/fft/UFFT.pas
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+{**********************************************************************
+
+  FFT.cpp
+
+  Dominic Mazzoni
+
+  September 2000
+
+***********************************************************************
+
+Fast Fourier Transform routines.
+
+  This file contains a few FFT routines, including a real-FFT
+  routine that is almost twice as fast as a normal complex FFT,
+  and a power spectrum routine when you know you don't care
+  about phase information.
+
+  Some of this code was based on a free implementation of an FFT
+  by Don Cross, available on the web at:
+
+    http://www.intersrv.com/~dcross/fft.html
+
+  The basic algorithm for his code was based on Numerican Recipes
+  in Fortran.  I optimized his code further by reducing array
+  accesses, caching the bit reversal table, and eliminating
+  float-to-double conversions, and I added the routines to
+  calculate a real FFT and a real power spectrum.
+
+***********************************************************************
+
+  Salvo Ventura - November 2006
+  Added more window functions:
+    * 4: Blackman
+    * 5: Blackman-Harris
+    * 6: Welch
+    * 7: Gaussian(a=2.5)
+    * 8: Gaussian(a=3.5)
+    * 9: Gaussian(a=4.5)
+
+***********************************************************************
+
+  This file is part of Audacity 1.3.4 beta (http://audacity.sourceforge.net/)
+  Ported to Pascal by the UltraStar Deluxe Team
+}
+
+unit UFFT;
+
+{$ifdef fpc}
+  {$mode delphi}{$H+}
+{$endif}
+
+interface
+type
+  TSingleArray = array[0..0] of Single;
+  PSingleArray = ^TSingleArray;
+
+procedure PowerSpectrum(NumSamples: Integer; In_, Out_: PSingleArray);
+procedure WindowFunc(NumSamples: Integer; in_: PSingleArray); inline;
+
+implementation
+
+uses
+  SysUtils;
+
+type TIntArray = array[0..0] of Integer;
+type TIntIntArray = array[0..0] of ^TIntArray;
+var gFFTBitTable: ^TIntIntArray;
+const MaxFastBits: Integer = 16;
+
+function IsPowerOfTwo(x: Integer): Boolean;
+begin
+   if (x < 2) then
+      result := false
+   else if ((x and (x - 1)) <> 0) then  { Thanks to 'byang' for this cute trick! }
+      result := false
+   else
+    result := true;
+end;
+
+function NumberOfBitsNeeded(PowerOfTwo: Integer): Integer;
+var i: Integer;
+begin
+  if (PowerOfTwo < 2) then begin
+    Writeln(ErrOutput, Format('Error: FFT called with size %d\n', [PowerOfTwo]));
+    Abort;
+  end;
+
+  i := 0;
+  while(true) do begin
+    if (PowerOfTwo and (1 shl i) <> 0) then begin
+      result := i;
+      Exit;
+    end;
+    Inc(i);
+  end;
+end;
+
+function ReverseBits(index, NumBits: Integer): Integer;
+var
+  i, rev: Integer;
+begin
+  rev := 0;
+  for i := 0 to NumBits-1 do begin
+    rev := (rev shl 1) or (index and 1);
+    index := index shr 1;
+  end;
+
+  result := rev;
+end;
+
+procedure InitFFT();
+var
+  len: Integer;
+  b, i: Integer;
+begin
+  GetMem(gFFTBitTable, MaxFastBits * sizeof(PSingle));
+
+  len := 2;
+  for b := 1 to MaxFastBits do begin
+    GetMem(gFFTBitTable^[b - 1], len * sizeof(Single));
+    for i := 0 to len-1 do
+      gFFTBitTable^[b - 1][i] := ReverseBits(i, b);
+      len := len shl 1;
+   end;
+end;
+
+function FastReverseBits(i, NumBits: Integer): Integer; inline;
+begin
+  if (NumBits <= MaxFastBits) then
+    result := gFFTBitTable[NumBits - 1][i]
+  else
+    result := ReverseBits(i, NumBits);
+end;
+
+{*
+ * Complex Fast Fourier Transform
+ *}
+procedure FFT(NumSamples: Integer;
+         InverseTransform: boolean;
+         RealIn, ImagIn, RealOut, ImagOut: PSingleArray);
+var
+  NumBits: Integer;                 { Number of bits needed to store indices }
+  i, j, k, n: Integer;
+  BlockSize, BlockEnd: Integer;
+  delta_angle: Double;
+  angle_numerator: Double;
+  tr, ti: Double;                   { temp real, temp imaginary }
+  sm2, sm1, cm2, cm1: Double;
+  w: Double;
+  ar0, ar1, ar2, ai0, ai1, ai2: Double;
+  denom: Single;
+begin
+
+   angle_numerator := 2.0 * Pi;
+
+   if (not IsPowerOfTwo(NumSamples)) then begin
+      Writeln(ErrOutput, Format('%d is not a power of two', [NumSamples]));
+      Abort;
+   end;
+
+   if (gFFTBitTable = nil) then
+      InitFFT();
+
+   if (InverseTransform) then
+      angle_numerator := -angle_numerator;
+
+   NumBits := NumberOfBitsNeeded(NumSamples);
+
+   {
+    **   Do simultaneous data copy and bit-reversal ordering into outputs...
+   }
+
+   for i := 0 to NumSamples-1 do begin
+      j := FastReverseBits(i, NumBits);
+      RealOut[j] := RealIn[i];
+      if(ImagIn = nil) then
+        ImagOut[j] := 0.0
+      else
+        ImagOut[j] := ImagIn[i];
+   end;
+
+   {
+    **   Do the FFT itself...
+   }
+
+   BlockEnd := 1;
+   BlockSize := 2;
+   while(BlockSize <= NumSamples) do
+   begin
+
+      delta_angle := angle_numerator / BlockSize;
+
+      sm2 := sin(-2 * delta_angle);
+      sm1 := sin(-delta_angle);
+      cm2 := cos(-2 * delta_angle);
+      cm1 := cos(-delta_angle);
+      w := 2 * cm1;
+
+      i := 0;
+      while(i < NumSamples) do
+      begin
+         ar2 := cm2;
+         ar1 := cm1;
+
+         ai2 := sm2;
+         ai1 := sm1;
+
+         j := i;
+         for n := 0 to BlockEnd-1 do
+         begin
+            ar0 := w * ar1 - ar2;
+            ar2 := ar1;
+            ar1 := ar0;
+
+            ai0 := w * ai1 - ai2;
+            ai2 := ai1;
+            ai1 := ai0;
+
+            k := j + BlockEnd;
+            tr := ar0 * RealOut[k] - ai0 * ImagOut[k];
+            ti := ar0 * ImagOut[k] + ai0 * RealOut[k];
+
+            RealOut[k] := RealOut[j] - tr;
+            ImagOut[k] := ImagOut[j] - ti;
+
+            RealOut[j] := RealOut[j] + tr;
+            ImagOut[j] := ImagOut[j] + ti;
+
+            Inc(j);
+         end;
+
+         Inc(i, BlockSize);
+      end;
+
+      BlockEnd := BlockSize;
+      BlockSize := BlockSize shl 1;
+   end;
+
+   {
+      **   Need to normalize if inverse transform...
+   }
+
+   if (InverseTransform) then begin
+      denom := NumSamples;
+
+      for i := 0 to NumSamples-1 do begin
+         RealOut[i] := RealOut[i] / denom;
+         ImagOut[i] := ImagOut[i] / denom;
+      end;
+   end;
+end;
+
+{*
+ * PowerSpectrum
+ *
+ * This function computes the same as RealFFT, above, but
+ * adds the squares of the real and imaginary part of each
+ * coefficient, extracting the power and throwing away the
+ * phase.
+ *
+ * For speed, it does not call RealFFT, but duplicates some
+ * of its code.
+ *}
+procedure PowerSpectrum(NumSamples: Integer; In_, Out_: PSingleArray);
+var
+  Half: Integer;
+  i: Integer;
+  theta: Single;
+  tmpReal, tmpImag, RealOut, ImagOut: PSingleArray;
+  wtemp: Single;
+  wpr, wpi, wr, wi: Single;
+  i3: Integer;
+  h1r, h1i, h2r, h2i, rt, it: Single;
+begin
+   Half := NumSamples div 2;
+
+   theta := Pi / Half;
+
+   GetMem(tmpReal, Half * sizeof(Single));
+   GetMem(tmpImag, Half * sizeof(Single));
+   GetMem(RealOut, Half * sizeof(Single));
+   GetMem(ImagOut, Half * sizeof(Single));
+
+   for i := 0 to Half-1 do begin
+      tmpReal[i] := In_[2 * i];
+      tmpImag[i] := In_[2 * i + 1];
+   end;
+
+   FFT(Half, false, tmpReal, tmpImag, RealOut, ImagOut);
+
+   wtemp := sin(0.5 * theta);
+
+   wpr := -2.0 * wtemp * wtemp;
+   wpi := sin(theta);
+   wr := 1.0 + wpr;
+   wi := wpi;
+
+   for i := 1 to (Half div 2)-1 do
+   begin
+      i3 := Half - i;
+
+      h1r := 0.5 * (RealOut[i] + RealOut[i3]);
+      h1i := 0.5 * (ImagOut[i] - ImagOut[i3]);
+      h2r := 0.5 * (ImagOut[i] + ImagOut[i3]);
+      h2i := -0.5 * (RealOut[i] - RealOut[i3]);
+
+      rt := h1r + wr * h2r - wi * h2i;
+      it := h1i + wr * h2i + wi * h2r;
+
+      Out_[i] := rt * rt + it * it;
+
+      rt := h1r - wr * h2r + wi * h2i;
+      it := -h1i + wr * h2i + wi * h2r;
+
+      Out_[i3] := rt * rt + it * it;
+
+      wtemp := wr;
+      wr := wtemp * wpr - wi * wpi + wr;
+      wi := wi * wpr + wtemp * wpi + wi;
+   end;
+
+   h1r := RealOut[0];
+   rt := h1r + ImagOut[0];
+   it := h1r - ImagOut[0];
+   Out_[0] := rt * rt + it * it;
+
+   rt := RealOut[Half div 2];
+   it := ImagOut[Half div 2];
+   Out_[Half div 2] := rt * rt + it * it;
+
+   FreeMem(tmpReal);
+   FreeMem(tmpImag);
+   FreeMem(RealOut);
+   FreeMem(ImagOut);
+end;
+
+procedure WindowFunc(NumSamples: Integer; in_: PSingleArray); inline;
+var
+  i: Integer;
+begin
+  for i := 0 to NumSamples-1 do
+    in_[i] := in_[i] * (0.50 - 0.50 * cos(2 * Pi * i / (NumSamples - 1)));
+end;
+
+end.