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multivid.html
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multivid.html
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<html>
<head>
<style>
document, body, #viewport {
width:100%;
height:100%;
border:0px;
margin:0px;
}
</style>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script>
///// Consider running Chrome like so:
// /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --video-threads=8 --allow-file-access-from-files
///// TODO:
// Draw video frames in actual spots
// Translate a bit while animating
// Increase # of videos
var videos = [];
var videos_ready = false;
var video_fps = 10;
var webgl_fps = 60;
var gl;
var shaderProgram;
function init_videos() {
var rows = 2;
var cols = 3;
var n = 0;
for (var y = 0; y < rows; y++) {
for (var x = 0; x < cols; x++) {
var video = $('<video>').attr('src', 'dfw/x' + x + 'y' + y + '.mp4')
videos.push({
video:video[0],
currentTexture:gl.createTexture(),
nextTexture:gl.createTexture(),
x:x,
y:y
});
}
}
console.log('Loading ' + videos.length + ' videos');
}
var webgl_frameno = 0;
function r2(x) {
return Math.round(x * 100) / 100;
}
// WebGL frames 0-5 are starting videos
// WebGL frames 6-11 are capturing video frame 0
// WebGL frames 12-17 show video frame 0
function sync_videos() {
var stat = [];
for (var i = 0; i < videos.length; i++) {
var v = videos[i];
// Desired time for video 0, at webgl frame 6, is the center of video frame 0 (t = 0.5 / video_fps)
var desired_time = (webgl_frameno - i) / webgl_fps - (0.5 / video_fps);
var actual_time = v.video.currentTime;
if (desired_time >= 0) {
if (v.video.paused) {
v.video.play();
}
// Set speed so that in one webgl frame, we'll be exactly at the right time
var future_target = (1 / webgl_fps) + desired_time;
var speed = (future_target - actual_time) / (1 / webgl_fps);
if (speed < 0.01) speed = 0.01;
if (speed > 5) speed = 5;
v.video.playbackRate = speed;
stat.push('d=' + r2(desired_time) + ',a=' + r2(actual_time) + ',s=' + r2(speed));
}
}
return stat.join(' ');
}
function capture_video_frame() {
var video_idx = webgl_frameno % (webgl_fps / video_fps);
var video_frameno = (webgl_frameno - video_idx) / (webgl_fps / video_fps) - 1;
if (video_idx < videos.length && video_frameno >= 0) {
var v = videos[video_idx];
gl.bindTexture(gl.TEXTURE_2D, v.nextTexture);
var before = performance.now();
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, v.video);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.bindTexture(gl.TEXTURE_2D, null);
var elapsed = performance.now() - before;
console.log(
'Grabbed frame ' + video_frameno +
' (actual ' + r2(v.video.currentTime * video_fps) +
') from video ' + video_idx + ' in ' + Math.round(elapsed) + ' ms');
}
}
function swap_video_textures() {
console.log('Swapping video textures');
for (var i = 0; i < videos.length; i++) {
var v = videos[i];
var tmp = v.currentTexture;
v.currentTexture = v.nextTexture;
v.nextTexture = v.currentTexture;
}
}
function draw_webgl_frame() {
if (webgl_frameno < 12) { return; }
gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clearColor(0, 0.5, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (webgl_frameno % (webgl_fps / video_fps) == 0) {
swap_video_textures();
}
for (var i = 0; i < videos.length; i++) {
var v = videos[i];
gl.bindTexture(gl.TEXTURE_2D, v.currentTexture);
gl.uniform2f(shaderProgram.uVideoOffset, v.x - 1 - webgl_frameno * 2e-3, -v.y);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
}
}
function animate() {
if (webgl_frameno < 11 + 29 * 6) window.requestAnimationFrame(animate);
if (!videos_ready) {
for (var i = 0; i < videos.length; i++) {
if (videos[i].video.readyState < 4) return;
}
videos_ready = true;
} else {
draw_webgl_frame();
capture_video_frame();
/*console.log(*/webgl_frameno + ':' + sync_videos()/*)*/;
webgl_frameno++;
}
}
function set_webgl_viewport() {
var viewport = $('#viewport')[0];
viewport.width = $(viewport).width();
viewport.height = $(viewport).height();
gl = viewport.getContext('webgl');
gl.viewportWidth = viewport.width;
gl.viewportHeight = viewport.height;
}
$(window).resize(set_webgl_viewport);
function init_webgl() {
set_webgl_viewport();
// Create shader program
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, getShader(gl, 'shader-vs'));
gl.attachShader(shaderProgram, getShader(gl, 'shader-fs'));
gl.linkProgram(shaderProgram);
gl.useProgram(shaderProgram);
shaderProgram.textureCoordAttribute =
gl.getAttribLocation(shaderProgram, 'aTextureCoord');
gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);
// Create texture coords in triangle-strip order
var quadTextureCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, quadTextureCoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]),
gl.STATIC_DRAW);
gl.vertexAttribPointer(shaderProgram.textureCoordAttribute,
2, gl.FLOAT, false, 0, 0);
shaderProgram.uVideoOffset = gl.getUniformLocation(shaderProgram, 'uVideoOffset');
}
function getShader(gl, id) {
var shaderScript = document.getElementById(id);
if (!shaderScript) {
return null;
}
var str = "";
var k = shaderScript.firstChild;
while (k) {
if (k.nodeType == 3) {
str += k.textContent;
}
k = k.nextSibling;
}
var shader;
if (shaderScript.type == "x-shader/x-fragment") {
shader = gl.createShader(gl.FRAGMENT_SHADER);
} else if (shaderScript.type == "x-shader/x-vertex") {
shader = gl.createShader(gl.VERTEX_SHADER);
} else {
return null;
}
gl.shaderSource(shader, str);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert(gl.getShaderInfoLog(shader));
return null;
}
return shader;
}
function init() {
init_webgl();
init_videos();
window.requestAnimationFrame(animate);
}
$(init);
</script>
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec2 vTextureCoord;
uniform sampler2D uSampler;
void main(void) {
vec4 textureColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
gl_FragColor = vec4(textureColor.rgb, 1);
//gl_FragColor = vec4(0,0,1,1);
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec2 aTextureCoord;
varying vec2 vTextureCoord;
uniform vec2 uVideoOffset;
uniform vec2 uVideoScale;
void main(void) {
vTextureCoord = vec2(aTextureCoord.x, 1.0 - aTextureCoord.y);
gl_Position = vec4(aTextureCoord + uVideoOffset, 0, 1);
}
</script>
</head>
<body>
<canvas id="viewport"></canvas>
</body>
</html>