Using new Unity VideoPlayer and VideoClip API to play video

Found the problem. Below is the FIXED code that plays Video and Audio:

//Raw Image to Show Video Images [Assign from the Editor]
public RawImage image;
//Video To Play [Assign from the Editor]
public VideoClip videoToPlay;

private VideoPlayer videoPlayer;
private VideoSource videoSource;

//Audio
private AudioSource audioSource;

// Use this for initialization
void Start()
{
    Application.runInBackground = true;
    StartCoroutine(playVideo());
}

IEnumerator playVideo()
{
    //Add VideoPlayer to the GameObject
    videoPlayer = gameObject.AddComponent<VideoPlayer>();

    //Add AudioSource
    audioSource = gameObject.AddComponent<AudioSource>();

    //Disable Play on Awake for both Video and Audio
    videoPlayer.playOnAwake = false;
    audioSource.playOnAwake = false;

    //We want to play from video clip not from url
    videoPlayer.source = VideoSource.VideoClip;

    //Set Audio Output to AudioSource
    videoPlayer.audioOutputMode = VideoAudioOutputMode.AudioSource;

    //Assign the Audio from Video to AudioSource to be played
    videoPlayer.EnableAudioTrack(0, true);
    videoPlayer.SetTargetAudioSource(0, audioSource);

    //Set video To Play then prepare Audio to prevent Buffering
    videoPlayer.clip = videoToPlay;
    videoPlayer.Prepare();

    //Wait until video is prepared
    while (!videoPlayer.isPrepared)
    {
        Debug.Log("Preparing Video");
        yield return null;
    }

    Debug.Log("Done Preparing Video");

    //Assign the Texture from Video to RawImage to be displayed
    image.texture = videoPlayer.texture;

    //Play Video
    videoPlayer.Play();

    //Play Sound
    audioSource.Play();

    Debug.Log("Playing Video");
    while (videoPlayer.isPlaying)
    {
        Debug.LogWarning("Video Time: " + Mathf.FloorToInt((float)videoPlayer.time));
        yield return null;
    }

    Debug.Log("Done Playing Video");
}

Why Audio was not playing:

//Set Audio Output to AudioSource
videoPlayer.audioOutputMode = VideoAudioOutputMode.AudioSource;

//Assign the Audio from Video to AudioSource to be played
videoPlayer.EnableAudioTrack(0, true);
videoPlayer.SetTargetAudioSource(0, audioSource);

must be called before videoPlayer.Prepare(); not after it. This is took hours of experiment to find this this was the problem I was having.

Stuck at "Preparing Video"?

Wait 5 seconds after videoPlayer.Prepare(); is called then exit the while loop.

Replace:

while (!videoPlayer.isPrepared)
{
    Debug.Log("Preparing Video");
    yield return null;
}

with:

//Wait until video is prepared
WaitForSeconds waitTime = new WaitForSeconds(5);
while (!videoPlayer.isPrepared)
{
    Debug.Log("Preparing Video");
    //Prepare/Wait for 5 sceonds only
    yield return waitTime;
    //Break out of the while loop after 5 seconds wait
    break;
}

This should work but you may experience buffering when the video starts playing. While using this temporary fix, my suggestion is to file for bug with the title of "videoPlayer.isPrepared always true" because this is a bug.

Some people also fixed it by changing:

videoPlayer.playOnAwake = false; 
audioSource.playOnAwake = false;

to

videoPlayer.playOnAwake = true; 
audioSource.playOnAwake = true;

Play Video From URL:

Replace:

//We want to play from video clip not from url
videoPlayer.source = VideoSource.VideoClip;

with:

//We want to play from url
videoPlayer.source = VideoSource.Url;
videoPlayer.url = "http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4";

then Remove:

public VideoClip videoToPlay; and videoPlayer.clip = videoToPlay; as these are not needed anymore.

Play Video From StreamingAssets folder:

string url = "file://" + Application.streamingAssetsPath + "/" + "VideoName.mp4";

if !UNITY_EDITOR && UNITY_ANDROID
    url = Application.streamingAssetsPath + "/" + "VideoName.mp4";
#endif

//We want to play from url
videoPlayer.source = VideoSource.Url;
videoPlayer.url = url;

All supported video formats:

• ogv
• vp8
• webm
• mov
• dv
• mp4
• m4v
• mpg
• mpeg

Extra supported video formats on Windows:

• avi
• asf
• wmf

Some of these formats don't work on some platforms. See this post for more information on supported video formats.

Similar to what the other answers have been saying. You could use callbacks for when preparing and end of video states. Rather than using coroutines and yield return.

videoPlayer.loopPointReached += EndReached;
videoPlayer.prepareCompleted += PrepareCompleted;

void PrepareCompleted(VideoPlayer vp) {
    vp.Play();
}

void EndReached(VideoPlayer vp) {
    // do something
}