Building HTML5 media (video, audio) controls with JavaScript

by , Oct. 19, 2010 at 08:59 PM

Scripts: html5

With te earlier versions of HTML, it was impossible to embed and play media on a webpage along without invoking third part plugins that didn't belong to HTML itself.
Here I am talking about Flash, Silverlight, Quick times, and so on...
The great HTML5 has come with handful and nice features to enrich and innovate the web applications.
One of these is the inclusion of MediaElement. (using Audio and/or video files on a webpage as we used to with images).
You do not need Flash any more to play you media on your page unless the visitors of your page still use the old browsers or so called, the non-Advanced browser.
Then you must foresee a way to a fallback for those browsers.
Not all browsers support yet HTML5 even IE8 (InternetExplorer8) doesn't support HTML5. However, Microsoft is promising to full integrate HTML5 in IE9, wich is to come.
Those browsers which support HTML5 have their custom media controls, which look differently to each other.
Here is the sketch of different controls of browsers:Native controls

If you want to build up you own customized Media controls, it is possible because HTML5 dispose Media properties, Media events you can manipulate in the DOM to control the media object and build your own media controls.


Media properties are:
"error", "src", "currentSrc", "networkState", "preload", "buffered", "readyState", "seeking", "currentTime", "startTime", "duration", "paused", "defaultPlaybackRate", "playbackRate", "played", "seekable", "ended", "autoplay", "loop", "controls", "volume", "muted"

Media events are:
"loadstart", "progress", "suspend", "emptied","stalled", "play","pause", "loadedmetadata", "loadeddata","waiting", "playing", "canplay", "canplaythrough", "seeking","seeked", "timeupdate", "ended", "ratechange", "durationchange", "volumechange"

All these properties and events are found in the spec. of W3 from May 2010.

Now the question is how to handle all this to build a controls. Most of these properties and events are more explanatory of its own. I cannot go explaining all these events and props on here otherwise it will be worth to write up a whole book on this.
But I will try to explain some.
Note that some of the props are read-only and cannot be change in value, others can be modified.
First of all a simple example of embed a video on a webpage:

Note to wacht this movie you have to use as web-browser (Mozilla Firefox, Safari, Chrome, or IE9) because the IE7 even IE8 cannot play the MediaElement Video or Audio and many other features of HTML5.

 

With this piece of code in this HTML page you wacht this video with a native custom controls accordingly  to the browser.

  1. //Check if the event loadstart is fired
  2. var myvideo = document.getElementsByTag('video')[0];
  3. myvideo.addEventListener('loadstart', function loadStart(){
  4. alert('Start loading...');
  5. }, false);
  6.  
  7. //Check if the event loadedmetadata is fired
  8. //var myvideo = document.getElementsByTag('video')[0];
  9. myvideo.addEventListener('loadedmetadata', function loadedData(){
  10. var videoOrigWidth = myvideo.videoWidth;
  11. var videoOrigHeight = myvideo.videoHeight;
  12. alert(videoOrigWidth + ' x ' + videoOrigHeight);
  13. }, false);
  14.  
  15. //
  16. //var myvideo = document.getElementsByTag('video')[0];
  17. var loaded_div = document.getElementById('loaded');
  18. myvideo.addEventListener('progress', Progress, false);
  19. function Progress(event) {
  20. if (event.total > 0) {
  21. loaded_div.innerHTML = (Math.floor(event.loaded / event.total * 100) + "% - " + myvideo.currentSrc);
  22. setLoadProgress((event.loaded / event.total));
  23. }
  24. }

 

In the code snippet here above you see some javascript code that may control the video element in HTML. Firstly, a defining a variable to hold the video element of the DOM when this is loaded and is ready. This video element is defined as follows var myvideo = document.getElementsByTag('video')[0];

myvideo is got from DOM which keep all the video elements in this case in an array. Because we are dealing with one video element that is why we take that first element of the array.

The loadstart and loadedmetadata are events that are fired when the media is successively the media data and metadata is start loading. Metadadata are related to the information of the media, its size, its author, ...

 

  1. // define the holders of currentTime and duration of the video
  2. var myvideo = document.getElementsByTag('video')[0];
  3. var videoDuration = document.getElementById('duration');
  4. var currentTime = document.getElementById('currentTime');
  5.  
  6. // Track the timeupdate Event, this event is important because
  7. // herein you receive periodically
  8. // the current time the video or audio has played
  9. myvideo.addEventListener('timeupdate', function(e) {
  10. //split currentTime (seconds) into separate hour/minute/second strings
  11. var seconds = e.target.currentTime;
  12. var h = Math.floor(seconds / 3600);
  13. seconds = seconds % 3600;
  14. var min = Math.floor(seconds / 60);
  15. seconds = Math.floor(seconds % 60);
  16. /* pad the minute and second strings to two digits */
  17. if (seconds.toString().length < 2)
  18. seconds = "0" + seconds;
  19. if (min.toString().length < 2)
  20. min = "0" + min;
  21. videoDuration.innerHTML = e.target.duration;
  22. currentTimeDisplay.innerHTML = h + ":" + min + ":" + seconds;
  23. }, false);

 

Here the the event timeupdate is useful, because when the media start to play it will be fired automatically and periocally within several milliseconds. It return an TimeRanges Object with the propriety for currentTime wich tells how much data has been played until now, one property for the total data of the video.

To let you see how to put into practice this simple explanation of javascript how to interact with a video. Of course to markup with html and CSS is more important to give your controls a nice feel and touch.

Click on Play to play the video, Pause to pause it and << Rewind to rewind it.

 

  1. var myvideo = document.getElementsByTag("video")[0];
  2. myvideo.addEventListenenr('timeupdate', function(e){
  3. var currentT_Holder = document.getElementById('currentT');
  4. currentT_Holder.innerHTML = e.target.currentTime;
  5. }, false);
  6. <video preload width="400">
  7. <source src="HTML5/MP4/video.mp4" type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"' />
  8. <source src="HTML5/MP4/video.ogv" type='video/ogg; codecs="theora, vorbis"' />
  9. <source src="HTML5/MP4/video.webm" type='video/webm; codecs="vp8, vorbis"'/>
  10. Your browser does not support the <code>video</code> element.
  11. </video>
  12. <p>
  13. <input type="button" value="Play" onclick="myvideo.play();" />
  14. <input type="button" value="Pause" onclick="myvideo.pause();" />
  15. <input type="button" value="<< Rewind" onclick="myvideo.currentTime = 0;">
  16. <span id="currentT"></span>
  17. </p>

 

For a complete build up controls with javascript and some CSS styling visit this link :
Customized HTML5 controls with javascript

Available Comments :

Amo

Oct. 20, 2010 at 11:36 PM

HTML5 is great stuff

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