Figured it.  change Pause to Stop.  Thanks again.

Thank  you so much... this is what i have been searching for.  one other question... I there any way to reset the video play when tracking is lost?

This really helped!! Thank you so much!!

Dear dpizzle　

Thank you for your suggestion.(and sorry for late reply)

I could do what I wanted to do.

I unchecked "Play On Awake" and edited 「DefaultTrackableEventHandler」 in the ImageTarget.

I could do when I find the marker then video plays and when marker loose then video pause(stop).

I attach my script below.

/*==============================================================================

Copyright (c) 2017 PTC Inc. All Rights Reserved.

Copyright (c) 2010-2014 Qualcomm Connected Experiences, Inc.

All Rights Reserved.

Confidential and Proprietary - Protected under copyright and other laws.

==============================================================================*/

using UnityEngine;

using Vuforia;

using UnityEngine.Video;      //added

/// <summary>

///     A custom handler that implements the ITrackableEventHandler interface.

/// </summary>

public class DefaultTrackableEventHandler : MonoBehaviour, ITrackableEventHandler

{

    #region PRIVATE_MEMBER_VARIABLES

    protected TrackableBehaviour mTrackableBehaviour;

    #endregion // PRIVATE_MEMBER_VARIABLES

    #region UNTIY_MONOBEHAVIOUR_METHODS

    protected virtual void Start()

    {

        mTrackableBehaviour = GetComponent<TrackableBehaviour>();

        if (mTrackableBehaviour)

            mTrackableBehaviour.RegisterTrackableEventHandler(this);

    }

    #endregion // UNTIY_MONOBEHAVIOUR_METHODS

    #region PUBLIC_METHODS

    /// <summary>

    ///     Implementation of the ITrackableEventHandler function called when the

    ///     tracking state changes.

    /// </summary>

    public void OnTrackableStateChanged(

        TrackableBehaviour.Status previousStatus,

        TrackableBehaviour.Status newStatus)

    {

        if (newStatus == TrackableBehaviour.Status.DETECTED ||

            newStatus == TrackableBehaviour.Status.TRACKED ||

            newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)

        {

            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");

            OnTrackingFound();

        }

        else if (previousStatus == TrackableBehaviour.Status.TRACKED &&

                 newStatus == TrackableBehaviour.Status.NOT_FOUND)

        {

            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " lost");

            OnTrackingLost();

        }

        else

        {

            // For combo of previousStatus=UNKNOWN + newStatus=UNKNOWN|NOT_FOUND

            // Vuforia is starting, but tracking has not been lost or found yet

            // Call OnTrackingLost() to hide the augmentations

            OnTrackingLost();

        }

    }

    #endregion // PUBLIC_METHODS

    #region PRIVATE_METHODS

    protected virtual void OnTrackingFound()

    {

        var rendererComponents = GetComponentsInChildren<Renderer>(true);

        var colliderComponents = GetComponentsInChildren<Collider>(true);

        var canvasComponents = GetComponentsInChildren<Canvas>(true);

        foreach (var component in rendererComponents)

            component.enabled = true;

        // Enable colliders:

        foreach (var component in colliderComponents)

            component.enabled = true;

        // Enable canvas':

        foreach (var component in canvasComponents)

            component.enabled = true;

        // added

        if (mTrackableBehaviour.gameObject.GetComponentInChildren<VideoPlayer>() != null)

        {

            mTrackableBehaviour.gameObject.GetComponentInChildren<VideoPlayer>().Play();

        }

    }

    protected virtual void OnTrackingLost()

    {

        var rendererComponents = GetComponentsInChildren<Renderer>(true);

        var colliderComponents = GetComponentsInChildren<Collider>(true);

        var canvasComponents = GetComponentsInChildren<Canvas>(true);

        // Disable rendering:

        foreach (var component in rendererComponents)

            component.enabled = false;

        // Disable colliders:

        foreach (var component in colliderComponents)

            component.enabled = false;

        // Disable canvas':

        foreach (var component in canvasComponents)

            component.enabled = false;

        // added

        if (mTrackableBehaviour.gameObject.GetComponentInChildren<VideoPlayer>() != null)

        {

            mTrackableBehaviour.gameObject.GetComponentInChildren<VideoPlayer>().Pause();

        }

    }

    #endregion // PRIVATE_METHODS

}

dpizzle , Thank you for your quick reply!!

(and sorry for late reply)

I checked the 「DefaultTrackableEventHandler」 and I tried some custom script  but it doesn't work well.

Actually I'm not familiar with #C and Unity...

what I want to do is below.2 and 3 are not done yet.

1. find target marker and display 3Dmodel  (this is OK . just using web cam I can find and display 3D model)

2. when I found the marker , I want to play video automatically.

3. when I lost the marker , I want to pause or stop video automatically.

■Question

Q1. In this case , how can I custom the script?

Do I need to create and attach new custom script to the Image Target or the Video Player's component?

(This time I use "Quad" 3D object and attach Video Player)

Or do I need to customize 「DefaultTrackableEventHandler」?

At the moment , just the easiest sample is OK.

if Anyone has the easiest sample or know the sample URL please tell me.

Thanks.

Yes you need some custom scripting.  Check out OnTrackingFound in DefaultTrackableEventHandler.  Uncheck play on awake, and in that method do something like: GameObject.Find("SomeGameObject").GetComponent<VideoPlayer>().Play();