uses
  EncdDecd;

procedure TForm3.Button1Click(Sender: TObject);
var
  fileStream: TFileStream;
  base64Stream: TStringStream;
begin
  // грузит файл с данными (в т.ч. бинарными)
  fileStream := TFileStream.Create('D:\test\file1.txt', fmOpenRead);
  base64Stream := TStringStream.Create;

  // кодирует поток в base64
  EncodeStream(fileStream, base64Stream);

  // показывает результат
  ShowMessage(base64Stream.DataString);

  FreeAndNil(fileStream);
  FreeAndNil(base64Stream);
end;

 MemoryStream := TMemoryStream.Create();
        BlobStream := TBlobStream.Create(TBlobField((frmDM.Select('SELECT fileblob FROM s_attachment WHERE ID=:pID', [TParamQuery.Create('pID', qSolutionsList.FieldByName('S_ATTACHMENT_ID').AsInteger)]).Fields[0])), bmRead);
        try
          MemoryStream.LoadFromStream(BlobStream);
          fsoAttachment.S['name'] := qSolutionsList.FieldByName('FILENAME').AsString;
          fsoAttachment.S['content'] := EncodeString(StreamToString(MemoryStream));
        finally
          BlobStream.Free;
          MemoryStream.Free;
        end;

var
  blobStream: TBlobStream;
  stringStream: TStringStream;
begin
  blobStream := TBlobStream.Create(TBlobField((frmDM.Select('SELECT fileblob FROM s_attachment WHERE ID=:pID',
    [TParamQuery.Create('pID', qSolutionsList.FieldByName('S_ATTACHMENT_ID').AsInteger)]).Fields[0])), bmRead);
  stringStream := TStringStream.Create;
  try
    EncodeStream(blobStream, stringStream);

    fsoAttachment.S['name'] := qSolutionsList.FieldByName('FILENAME').AsString;
    fsoAttachment.S['content'] := stringStream.DataString;
  finally
    blobStream.Free;
    stringStream.Free;
  end;
end;