function explain, help! getAudioFileDuration()

[MIKHANYA]

Need help, please explain how to use this functiongetAudioFileDuration() I'm trying to read file duration on SD card.
Code that posted in wiki page, https://github.com/schreibfaul1/ESP32-audioI2S/wiki#what-else-is-there what is ticker ? It doesn't compile with includes like

#include "Arduino.h"
#include "WiFiMulti.h"
#include "Audio.h"
#include "SPI.h"
#include "SD.h"
#include "FS.h"

Ticker ticker;
void setup()  {
	...
	ticker.attach(1, tcr1s);
	...
}

void tcr1s(){
    uint32_t act=audio.getAudioCurrentTime();
    uint32_t afd=audio.getAudioFileDuration();
    uint32_t pos =audio.getFilePos();
    log_i("pos =%i", pos);
    log_i("audioTime: %i:%02d - duration: %i:%02d", (act/60), (act%60) , (afd/60), (afd%60));
}

[schreibfaul1]

Ticker is a class in Ticker.h that periodically calls an interrupt via a callback function.
Please try #include "Ticker.h", I think that's missing in the example