MovieTexture has been deprecated. Refer to the new movie playback solution VideoPlayer.
The time, in seconds, that the movie takes to play back completely. Note that duration is only available once the movie has started. Until then duration will return -1. If you need to know the duration of a movie before it is played, consider extracting this information offline and creating a text asset. You can then look up the duration given the movie name.
using UnityEngine;
public class Example : MonoBehaviour { MovieTexture mov; GUIText gui;
void Start() { gui.text = mov.duration.ToString(); } }