Автор: http://www.swissdelphicenter.ch

uses
  VfW { from download };

function GrabAVIFrame(avifn: string; iFrameNumber: Integer; ToFileName:
  TFileName): Boolean;
var
  Error: Integer;
  pFile: PAVIFile;
  AVIStream: PAVIStream;
  gapgf: PGETFRAME;
  lpbi: PBITMAPINFOHEADER;
  bits: PChar;
  hBmp: HBITMAP;
  AviInfo: TAVIFILEINFOW;
  sError: string;
  TmpBmp: TBitmap;
  DC_Handle: HDC;
begin
  Result := False;
  // Initialize the AVIFile library.
  AVIFileInit;

  // The AVIFileOpen function opens an AVI file
  Error := AVIFileOpen(pFile, PChar(avifn), 0, nil);
  if Error <> 0 then
  begin
    AVIFileExit;
    case Error of
      AVIERR_BADFORMAT: sError := 'The file couldnot be read';
      AVIERR_MEMORY: sError :=
        'The file could not be opened because of insufficient memory.';
      AVIERR_FILEREAD: sError :=
        'A disk error occurred while reading the file.';
      AVIERR_FILEOPEN: sError :=
        'A disk error occurred while opening the file.';
    end;
    ShowMessage(sError);
    Exit;
  end;

  // AVIFileInfo obtains information about an AVI file
  if AVIFileInfo(pFile, @AVIINFO, SizeOf(AVIINFO)) <> AVIERR_OK then
  begin
    // Clean up and exit
    AVIFileRelease(pFile);
    AVIFileExit;
    Exit;
  end;

  // Show some information about the AVI
  Form1.Memo1.Lines.Add('AVI Width : ' + IntToStr(AVIINFO.dwWidth));
  Form1.Memo1.Lines.Add('AVI Height : ' + IntToStr(AVIINFO.dwHeight));
  Form1.Memo1.Lines.Add('AVI Length : ' + IntToStr(AVIINFO.dwLength));

  // Open a Stream from the file
  Error := AVIFileGetStream(pFile, AVIStream, streamtypeVIDEO, 0);
  if Error <> AVIERR_OK then
  begin
    // Clean up and exit
    AVIFileRelease(pFile);
    AVIFileExit;
    Exit;
  end;

  // Prepares to decompress video frames
  gapgf := AVIStreamGetFrameOpen(AVIStream, nil);
  if gapgf = nil then
  begin
    AVIStreamRelease(AVIStream);
    AVIFileRelease(pFile);
    AVIFileExit;
    Exit;
  end;

  // Read current Frame
  // AVIStreamGetFrame Returns the address of a decompressed video frame
  lpbi := AVIStreamGetFrame(gapgf, iFrameNumber);
  if lpbi = nil then
  begin
    AVIStreamGetFrameClose(gapgf);
    AVIStreamRelease(AVIStream);
    AVIFileRelease(pFile);
    AVIFileExit;
    Exit;
  end;

  // Show number of frames:
  Form1.Memo1.Lines.Add(Format('Framstart: %d FrameEnd: %d',
    [AVIStreamStart(AVIStream), AVIStreamEnd(AVIStream)]));

  TmpBmp := TBitmap.Create;
  try
    TmpBmp.Height := lpbi.biHeight;
    TmpBmp.Width := lpbi.biWidth;
    bits := Pointer(Integer(lpbi) + SizeOf(TBITMAPINFOHEADER));

    DC_Handle := CreateDC('Display', nil, nil, nil);
    try
      hBmp := CreateDIBitmap(DC_Handle, // handle of device context
        lpbi^, // address of bitmap size and format data
        CBM_INIT, // initialization flag
        bits, // address of initialization data
        PBITMAPINFO(lpbi)^, // address of bitmap color-format data
        DIB_RGB_COLORS); // color-data usage
    finally
      DeleteDC(DC_Handle);
    end;

    TmpBmp.Handle := hBmp;
    AVIStreamGetFrameClose(gapgf);
    AVIStreamRelease(AVIStream);
    AVIFileRelease(pfile);
    AVIFileExit;
    try
      TmpBmp.SaveToFile(ToFileName);
      Result := True;
    except
    end;
  finally
    TmpBmp.Free;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  // Extract Frame 3 from AVI file
  GrabAVIFrame('C:\Test.avi', 3, 'c:\avifram.bmp');
end;