#

API Documentation for: NEXT
Show: Inherited Protected Private Deprecated

# File:VideoBuffer.js

    /*
    * VideoBuffer
    * Visit http://createjs.com/ for documentation, updates and examples.
    *
    * Copyright (c) 2010 gskinner.com, inc.
    *
    * Permission is hereby granted, free of charge, to any person
    * obtaining a copy of this software and associated documentation
    * files (the "Software"), to deal in the Software without
    * restriction, including without limitation the rights to use,
    * copy, modify, merge, publish, distribute, sublicense, and/or sell
    * copies of the Software, and to permit persons to whom the
    * Software is furnished to do so, subject to the following
    * conditions:
    *
    * The above copyright notice and this permission notice shall be
    * included in all copies or substantial portions of the Software.
    *
    * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
    * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
    * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
    * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
    * OTHER DEALINGS IN THE SOFTWARE.
    */

    /**
     * @module EaselJS
     */

    // namespace:
    this.createjs = this.createjs||{};

    (function() {
    	"use strict";

    // constructor:
    	/**
    	 * When an HTML video seeks, including when looping, there is an indeterminate period before a new frame is available.
    	 * This can result in the video blinking or flashing when it is drawn to a canvas. The VideoBuffer class resolves
    	 * this issue by drawing each frame to an off-screen canvas and preserving the prior frame during a seek.
    	 *
    	 * 	var myBuffer = new createjs.VideoBuffer(myVideo);
    	 * 	var myBitmap = new Bitmap(myBuffer);
    	 *
    	 * @class VideoBuffer
    	 * @param {HTMLVideoElement} video The HTML video element to buffer.
    	 * @constructor
    	 **/
    	function VideoBuffer(video) {

    	// private properties:
    		/**
    		 * Used by Bitmap to determine when the video buffer is ready to be drawn. Not intended for general use.
    		 * @property readyState
    		 * @protected
    		 * @type {Number}
    		 * @default 0
    		 **/
    		this.readyState = video.readyState;

    		/**
    		 * @property _video
    		 * @protected
    		 * @type {HTMLVideoElement}
    		 * @default 0
    		 **/
    		this._video = video;

    		/**
    		 * @property _canvas
    		 * @protected
    		 * @type {HTMLCanvasElement}
    		 * @default 0
    		 **/
    		this._canvas = null;

    		/**
    		 * @property _lastTime
    		 * @protected
    		 * @type {Number}
    		 * @default -1
    		 **/
    		this._lastTime = -1;

    		if (this.readyState < 2) { video.addEventListener("canplaythrough", this._videoReady.bind(this)); } //once:true isn't supported everywhere, but its a non-critical optimization here.
    	}
    	var p = VideoBuffer.prototype;

    // public methods:
    	/**
    	 * Gets an HTML canvas element showing the current video frame, or the previous frame if in a seek / loop.
    	 * Primarily for use by {{#crossLink "Bitmap"}}{{/crossLink}}.
    	 * @method getImage
    	 **/
    	p.getImage = function() {
    		if (this.readyState < 2) { return; }
    		var canvas=this._canvas, video = this._video;
    		if (!canvas) {
    			canvas = this._canvas = createjs.createCanvas?createjs.createCanvas():document.createElement("canvas");
    			canvas.width = video.videoWidth;
    			canvas.height = video.videoHeight;
    		}
    		if (video.readyState >= 2 && video.currentTime !== this._lastTime) {
    			var ctx = canvas.getContext("2d");
    			ctx.clearRect(0,0,canvas.width,canvas.height);
    			ctx.drawImage(video,0,0,canvas.width,canvas.height);
    			this._lastTime = video.currentTime;
    		}
    		return canvas;
    	};

    // private methods:
    	/**
    	 * @method _videoReady
    	 * @protected
    	 **/
    	p._videoReady = function() {
    		this.readyState = 2;
    	};

    	createjs.VideoBuffer = VideoBuffer;
    }());