WebGL performance improvements: re-use texture data

src/mpeg1.js

 
 	// Invoke decode callbacks
 	if (this.destination) {
-		this.destination.render(this.currentY, this.currentCr, this.currentCb);
+		this.destination.render(this.currentY, this.currentCr, this.currentCb, true);
 	}
 
 	// If this is a reference picutre then rotate the prediction pointers

src/webgl.js

 	this.height = this.canvas.height;
 	this.enabled = true;
 
+	this.hasTextureData = {};
+
 	var contextCreateOptions = {
 		preserveDrawingBuffer: !!options.preserveDrawingBuffer,
 		alpha: false,
 		depth: false,
 		stencil: false,
-		antialias: false
+		antialias: false,
+		premultipliedAlpha: false
 	};
 
 	this.gl = 
 	var gl = this.gl;
 	var vertexAttr = null;
 
+	gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);
+
 	// Init buffers
 	this.vertexBuffer = gl.createBuffer();
 	var vertexCoords = new Float32Array([0, 0, 0, 1, 1, 0, 1, 1]);
 	gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
 };
 
-WebGLRenderer.prototype.render = function(y, cb, cr) {
+WebGLRenderer.prototype.render = function(y, cb, cr, isClampedArray) {
 	if (!this.enabled) {
 		return;
 	}
 	// In some browsers WebGL doesn't like Uint8ClampedArrays (this is a bug
 	// and should be fixed soon-ish), so we have to create a Uint8Array view 
 	// for each plane.
-	if (this.shouldCreateUnclampedViews) {
+	if (isClampedArray && this.shouldCreateUnclampedViews) {
 		y = new Uint8Array(y.buffer),
 		cb = new Uint8Array(cb.buffer),
 		cr = new Uint8Array(cr.buffer);	
 	var gl = this.gl;
 	gl.activeTexture(unit);
 	gl.bindTexture(gl.TEXTURE_2D, texture);
-	gl.texImage2D(
-		gl.TEXTURE_2D, 0, gl.LUMINANCE, w, h, 0, 
-		gl.LUMINANCE, gl.UNSIGNED_BYTE, data
-	);
+
+	if (this.hasTextureData[unit]) {
+		gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, w, h, gl.LUMINANCE, gl.UNSIGNED_BYTE, data);
+	}
+	else {
+		this.hasTextureData[unit] = true;
+		gl.texImage2D(
+			gl.TEXTURE_2D, 0, gl.LUMINANCE, w, h, 0, 
+			gl.LUMINANCE, gl.UNSIGNED_BYTE, data
+		);
+	}
 }
 
 WebGLRenderer.IsSupported = function() {