type
  TDataArray = Array of Byte;
  TWordDataArray = Array of Word;

procedure DrawOscilloscope (Buffer: PChar; Size: Integer;
                            OscRight, OscLeft: TBitmap;
                            LW, LH, RW, RH: Integer);

  // ----------------

  procedure CreateLocalBitmaps (var bmpL, bmpR: TBitmap);
  begin
    bmpL := TBitmap.Create;
    bmpL.Width := LW;
    bmpL.Height := LH;

    // ****

    bmpL.Canvas.Pen.Width := 1;
    bmpL.Canvas.Pen.Color := clRed;

    bmpL.Canvas.MoveTo (0, round (bmpL.Height / 2));
    bmpL.Canvas.LineTo (bmpL.Width, round (bmpL.Height / 2));

    bmpL.Canvas.Pen.Width := 1;
    bmpL.Canvas.Pen.Color := clGreen;

    // ****

    bmpR := TBitmap.Create;
    bmpR.Width := RW;
    bmpR.Height := RH;

    // ****

    bmpR.Canvas.Pen.Width := 1;
    bmpR.Canvas.Pen.Color := clRed;

    bmpR.Canvas.MoveTo (0, round (bmpR.Height / 2));
    bmpR.Canvas.LineTo (bmpR.Width, round (bmpR.Height / 2));

    bmpR.Canvas.Pen.Width := 1;
    bmpR.Canvas.Pen.Color := clGreen;
  end;

  // ----------------

  procedure FreeLocalBitmaps (var bmpL, bmpR: TBitmap);
  begin
    FreeAndNil (bmpL);
    FreeAndNil (bmpR);
  end;

  // ----------------

  procedure FillBuffer (Buffer: PChar; StartIndex, BufferSize: Integer;
    out FilledBuffer: TDataArray);
  var
    a, b: Integer;
  begin
    SetLength (FilledBuffer, 0);

    a := StartIndex;
    repeat
      b := Length (FilledBuffer);
      SetLength (FilledBuffer, b + 1);
      FilledBuffer[b] := Byte (Buffer[a]);
      inc (a, 2);
      if (a > BufferSize) then
        break;
    until FALSE;
  end;

  // ----------------

  procedure CheckBufferLengths (var BufferL, BufferR: TDataArray);
  var
    l1, l2: Integer;
  begin
    l1 := Length (BufferL);
    l2 := Length (BufferR);

    if (l1 > l2) then
      begin
        SetLength (BufferL, l2);
        l1 := l2;
      end;

    if (l2 > l1) then
      begin
        SetLength (BufferR, l1);
        l2 := l1;
      end;
  end;

  // ----------------

  procedure MakeWordBuffer (Buffer: TDataArray; var WordBuffer: TWordDataArray);
  var
    a, b, l: Integer;
  begin
    SetLength (WordBuffer, 0);

    // ****

    l := Length (Buffer);
    a := 0;
    repeat
      b := Length (WordBuffer);
      SetLength (WordBuffer, b + 1);

      WordBuffer[b] := MakeWord (Buffer[a + 1], Buffer[a]);

      inc (a, 2);
      if (a > l) then
        break;
    until FALSE;
  end;

  // ----------------

  function SampleToScreen (Buffer: TWordDataArray; SampleIndex: Integer):Integer;
  begin
    Result := Round (Buffer[SampleIndex] * LH / High (Word));
  end;

var
  BufferL, BufferR: TDataArray;

  WordBufferL,
  WordBufferR: TWordDataArray;

  b, a, N: Integer;

  bmpL,
  bmpR: TBitmap;
begin

  // Lokale temp. Bitmaps erstellen
  CreateLocalBitmaps (bmpL, bmpR);

  // ****

  // Puffer nach L & R trennen
  FillBuffer (Buffer, 0, Size, BufferL);
  FillBuffer (Buffer, 1, Size, BufferR);

  // ****

  // Pufferlängen ggf. abgleichen
  CheckBufferLengths (BufferL, BufferR);

  // ****

  // Puffer-Bytes nach Word konvertieren
  MakeWordBuffer (BufferL, WordBufferL);
  MakeWordBuffer (BufferR, WordBufferR);

  // ****

  // In lokale Bitmaps zeichnen ...
  bmpL.Canvas.LineTo (0, SampleToScreen (WordBufferL, 0));
  bmpR.Canvas.LineTo (0, SampleToScreen (WordBufferR, 0));

  N := Size div 4;
  b := LW;
  if N < b then
    b := N;

  for a := 0 to b - 1 do
    begin
      bmpL.Canvas.LineTo (round (a * LW / b), SampleToScreen (WordBufferL, round (a * N / b)));
      bmpR.Canvas.LineTo (round (a * LW / b), SampleToScreen (WordBufferR, round (a * N / b)));
    end;

  // ... und an "öffentliche" Bitmaps übergeben
  OscLeft.Assign (bmpL);
  OscRight.Assign (bmpR);

  // Daten freigeben
  FreeLocalBitmaps (bmpL, bmpR);
end;