sub _getoffset {
my ($shelf,$args) = @_;
my $frame = \$args->{'frame'};
my $index = \$args->{'index'};
my $startpos = ( $ACHT * ${$frame} ) ;
if ( not ( ${$index} ) ) { return ('index not found in _getoffset'); }

my $ok = 'false';
my $offsetrc = q{};
my $filenorc = q{};

my $buffer = \$shelf->_readindex({index=>${$index},frame=>${$frame},});
my ($frameoffset,undef,$independent,$filenumber) = unpack 'ssss', ${$buffer};
  $offsetrc = hex $frameoffset;
  $filenorc = hex $filenumber;
  print "_getoffsetstart || frame ${$frame} hex $frameoffset <-> dez $offsetrc in file $filenorc\n";
return ($offsetrc,$filenorc);
}