Rogue Robotics rmp3 player - Gettracklength() Command

Other Hardware Audio
1

Hi:
I am trying to use the command gettracklength() to retrieve the length of an mp3 track, but not having much luck. Probably I am not using the correct syntax.
I am posting the code below. Note that I am using the rmp3 shield with an Arduino Mega. The target file is in the root directory of the SD card.

Any help will be gtreatly appreciated.
Robbie.

#include <RogueMP3.h>
#include <RogueSD.h> 

RogueMP3 rmp3(Serial1);
RogueSD filecommands(Serial1); 

void setup()
{
  Serial.begin(9600);
  Serial1.begin(9600); 
  rmp3.sync();
  rmp3.stop(); 
  const char *path = "";
  const char *filename = "/mysong.mp3";
  
  int16_t lengthOfTrack;
  lengthOfTrack = rmp3.gettracklength(filename);
  delay(200);
  Serial.println(lengthOfTrack);
  Serial.println(rmp3.LastErrorCode, HEX);
  rmp3.playfile(filename);
}
 
void loop()
{
  
}