如果 source是 videoclip（以下两种方式都可以）：

  _videoPlayer.Play();
        Debug.Log("time: " + _videoPlayer.clip.length);
        _videoPlayer.time = 10;

[SerializeField] VideoPlayer videoPlayer;

public void SetClipWithTime(VideoClip clip, float time) 
{
    StartCoroutine (SetTimeRoutine(clip, time));
}

IEnumerator SetTimeRoutine (VideoClip clip, float time)
{
    if(videoPlayer.isPlaying)
    {
        videoPlayer.Stop();
    }

    videoPlayer.clip = clip;

    videoPlayer.Prepare();
    yield return new WaitUntil (() => videoPlayer.isPrepared);  
    yield return new WaitUntil (() => videoPlayer.canSetTime);

    videoPlayer.Play();
    videoPlayer.time = time;
}

如果是source是URL：

IEnumerator VideoPlay()
    {
        _videoPlayer.Prepare();

        yield return new WaitUntil(() => _videoPlayer.isPrepared);
        yield return new WaitUntil(() => _videoPlayer.canSetTime);
        // 检查是否完成初始化
        //while (!_videoPlayer.isPrepared)
        //{
        //    yield return new WaitForSeconds(1f);
        //    break;
        //}
        // 设置开头是第100帧
        _videoPlayer.frame += 100;
        // 开始播放
        _videoPlayer.Play();
        yield return new WaitForSeconds(0.01f);
        _videoPlayer.Pause();
    }

 IEnumerator VideoPlay()
    {
        _videoPlayer.Prepare();
        // 检查是否完成初始化
        while (!_videoPlayer.isPrepared)
        {
            yield return new WaitForSeconds(1f);
            break;
        }
        // 设置开头是第100帧
        _videoPlayer.frame += 100;
        // 开始播放
        _videoPlayer.Play();
        //yield return new WaitForSeconds(0.01f);
        //_videoPlayer.Pause();
    }