protected function saveConversionCommand()
 {
     if (!$this->conv_cmd) {
         throw new kConversionException("ConversionCommand not yet created");
     }
     // depending on the transcoder - decide on the server's path
     $server_path = $this->server_cmd_path;
     if ($this->conv_cmd->commercial_transcoder && $this->commercial_server_cmd_path) {
         $server_path = $this->commercial_server_cmd_path;
     }
     $cmd_file = $server_path . "/" . basename($this->conv_cmd->source_file);
     $this->conv_cmd->toFile($cmd_file, true);
     return $cmd_file;
 }