Example of how to embedding a video within a Script Editor Webpart (SharePoint Online), using the Office 365 Video Portal REST API

VideoPlayer.js

var PlayVideo = function (chid, vid) {
	var rootURL = window.location.protocol + "//" + window.location.host;
	var siteURL = rootURL + '/portals/hub'
	var wsPath = '/_api/VideoService/Channels(guid\'' + chid + '\')/Videos(guid\'' + vid + '\')?$Select=Title,Description,CreatedDate,DefaultEmbedCode,VideoDurationInSeconds,ID,VideoProcessingStatus,ThumbnailUrl';
	var followAPI = siteURL + wsPath;

	var getVideo = function () {
		jQuery.ajax({
			url: followAPI,
			headers: {
				"accept": "application/json;odata=verbose"
			},
			success: videoContentRetrieved,
			error: requestFailed
		});
	}

	var videoContentRetrieved = function (data) {
		var stringData = JSON.stringify(data);
		var jsonObject = JSON.parse(stringData);
		var videoTitle = jsonObject.d.Title;
		var videoEmbed = jsonObject.d.DefaultEmbedCode;
		var videoStatus = jsonObject.d.VideoProcessingStatus

		var htmlBody = '';
		htmlBody += '<h3>' + videoTitle + '</h3>';
		if (videoStatus === 2) {
			htmlBody += '<div>' + videoEmbed + '</div>';
		} else {
			/*
			VideoProcessingStatus -- The status of the video processing. Can take the following values:
				0 -- (default) -- The video has not yet been processed for playback.
				1 -- The video has been picked up and is being processed.
				2 -- The video is ready to play.
				3 -- The video encountered an error while it was being uploaded to Azure Media Services for processing.
				4 -- Error -- Generic error--Unable to process the video for streaming.
				5 -- Error -- Timeout error--Unable to process the video for streaming.
				6 -- Error -- Unsupported format --The video file type is not supported for streaming playback by Azure Media Services.
			*/
			htmlBody += '<div>Unable to process the video for streaming, please try again later.</div>';
		}

		jQuery("div.highlightedVideo").html(htmlBody);
	}

	var requestFailed = function (xhr, ajaxOptions, thrownError) {
		alert('Error:\n' + xhr.status + '\n' + thrownError + '\n' + xhr.responseText);
	}

	SP.SOD.executeFunc('sp.js', 'SP.ClientContext', getVideo);
}

VideoPlayer.webpart

<webParts>
  <webPart xmlns="http://schemas.microsoft.com/WebPart/v3">
    <metaData>
      <type name="Microsoft.SharePoint.WebPartPages.ScriptEditorWebPart, Microsoft.SharePoint, Version=16.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" />
      <importErrorMessage>Cannot import this Web Part.</importErrorMessage>
    </metaData>
    <data>
      <properties>
        <property name="ExportMode" type="exportmode">All</property>
        <property name="HelpUrl" type="string" />
        <property name="Hidden" type="bool">False</property>
        <property name="Description" type="string">Display a video within a webpart.</property>
        <property name="Content" type="string">
          &lt;script type="text/javascript" src="/Style%20Library/_Custom/VideoPlayer.js" /&gt;
          &lt;div class="highlightedVideo"&gt;&lt;/div&gt;
          &lt;script type="text/javascript"&gt;
          jQuery(document).ready(function() {
          var chid = '00000000-0000-0000-0000-000000000000';
          var vid = '00000000-0000-0000-0000-000000000000';
          PlayVideo(chid, vid);
          });
          &lt;/script&gt;
        </property>
        <property name="CatalogIconImageUrl" type="string" />
        <property name="Title" type="string">Video player</property>
        <property name="AllowHide" type="bool">True</property>
        <property name="AllowMinimize" type="bool">True</property>
        <property name="AllowZoneChange" type="bool">True</property>
        <property name="TitleUrl" type="string" />
        <property name="ChromeType" type="chrometype">TitleAndBorder</property>
        <property name="AllowConnect" type="bool">True</property>
        <property name="Width" type="unit" />
        <property name="Height" type="unit" />
        <property name="HelpMode" type="helpmode">Navigate</property>
        <property name="AllowEdit" type="bool">True</property>
        <property name="TitleIconImageUrl" type="string" />
        <property name="Direction" type="direction">NotSet</property>
        <property name="AllowClose" type="bool">True</property>
        <property name="ChromeState" type="chromestate">Normal</property>
      </properties>
    </data>
  </webPart>
</webParts>