DivX Calculator: Video Bitrate/Audio Bitrate/Resolution

Jeff Mott · 09-27-2003, 08:40 PM

Code:

/*
 * var divx_video = new DivXVideo();
 */
function DivXVideo()
{
    /*
     * default values
     */
    this.VideoLength = 0;
    this.AspectRatio = 16 / 9;
    this.Width = 720;
    this.Height = 480;
    this.CroppingTop = 0;
    this.CroppingRight = 0;
    this.CroppingBottom = 0;
    this.CroppingLeft = 0;
    this.FramesPerSecond = 23.976;
    this.OutputFileSize = 703.125;
    this.ResXModulus = 4;
    this.ResYModulus = 2;
    this.AudioBitrateModulus = 16;
    
    /*
     * videoLength();
     * videoLength( seconds );
     * videoLength( minutes, seconds );
     * videoLength( hours, minutes, seconds );
     */
    this.videoLength = function()
    {
        if (arguments.length > 2)
            this.VideoLength = arguments[0] * 3600 + arguments[1] * 60 + arguments[2];
        else if (arguments.length > 1)
            this.VideoLength = arguments[0] * 60 + arguments[1];
        else if (arguments.length)
            this.VideoLength = arguments[0];
        return this.VideoLength;
    }
    
    /*
     * aspectRatio( [ ratio ] );
     */
    this.aspectRatio = function()
    {
        if (arguments.length)
            this.AspectRatio = arguments[0];
        return this.AspectRatio;
    }
    
    /*
     * width( [ n ] );
     */
    this.width = function()
    {
        if (arguments.length)
            this.Width = arguments[0];
        return this.Width;
    }
    
    /*
     * height( [ n ] );
     */
    this.height = function()
    {
        if (arguments.length)
            this.Height = arguments[0];
        return this.Height;
    }
    
    /*
     * croppingTop( [ n ] );
     */
    this.croppingTop = function()
    {
        if (arguments.length)
            this.CroppingTop = arguments[0];
        return this.CroppingTop;
    }
    
    /*
     * croppingRight( [ n ] );
     */
    this.croppingRight = function()
    {
        if (arguments.length)
            this.CroppingRight = arguments[0];
        return this.CroppingRight;
    }
    
    /*
     * croppingBottom( [ n ] );
     */
    this.croppingBottom = function()
    {
        if (arguments.length)
            this.CroppingBottom = arguments[0];
        return this.CroppingBottom;
    }
    
    /*
     * croppingLeft( [ n ] );
     */
    this.croppingLeft = function()
    {
        if (arguments.length)
            this.CroppingLeft = arguments[0];
        return this.CroppingLeft;
    }
    
    /*
     * framesPerSecond( [ fps ] );
     */
    this.framesPerSecond = function()
    {
        if (arguments.length)
            this.FramesPerSecond = arguments[0];
        return this.FramesPerSecond;
    }
    
    /*
     * outputFileSize( [ MB ] );
     */
    this.outputFileSize = function()
    {
        if (arguments.length)
            this.OutputFileSize = arguments[0];
        return this.OutputFileSize;
    }
    
    /*
     * resXModulus( [ modulus ] );
     */
    this.resXModulus = function()
    {
        if (arguments.length)
            this.ResXModulus = arguments[0];
        return this.ResXModulus;
    }
    
    /*
     * resYModulus( [ modulus ] );
     */
    this.resYModulus = function()
    {
        if (arguments.length)
            this.ResYModulus = arguments[0];
        return this.ResYModulus;
    }
    
    /*
     * audioBitrateModulus( [ modulus ] );
     */
    this.audioBitrateModulus = function()
    {
        if (arguments.length)
            this.AudioBitrateModulus = arguments[0];
        return this.AudioBitrateModulus;
    }
    
    /*
     * audioBitrate();
     *
     * Assume MP3 compression.
     * Variable dependencies:
     *  - outputFileSize
     *  - videoLength
     *  - audioBitrateModulus
     */
    this.audioBitrate = function()
    {
        var kbps = Math.round(this.OutputFileSize * 8192 / (this.VideoLength * 7.09375));
        kbps -= kbps % this.AudioBitrateModulus;
        return kbps > 128 ? 128 : kbps;
    }
    
    /*
     * videoBitrate();
     *
     * Variable dependencies:
     *  - outputFileSize
     *  - videoLength
     *  - audioBitrateModulus
     */
    this.videoBitrate = function()
    {
        return Math.floor((this.OutputFileSize - this.kbps2MB(this.audioBitrate(), this.VideoLength)) * 8192 / this.VideoLength);
    }
    
    /*
     * resX();
     *
     * Variable dependencies:
     *  - width
     *  - croppingLeft
     *  - croppingRight
     *  - height
     *  - croppingTop
     *  - croppingBottom
     *  - aspectRatio
     *  - outputFileSize
     *  - videoLength
     *  - audioBitrateModulus
     *  - framesPerSecond
     *  - resXModulus
     */
    this.resX = function()
    {
        var x = this.Width - this.CroppingLeft - this.CroppingRight;
        var y = this.Height - this.CroppingTop - this.CroppingBottom;
        if (Math.round(this.Width / this.AspectRatio) > this.Height)
            x /= this.Width / Math.round(this.Height * this.AspectRatio)
        else
            y /= this.Height / Math.round(this.Width / this.AspectRatio);
        var optimum_res_x = Math.sqrt(1024 * this.videoBitrate() * (x / y) / (.2 * this.FramesPerSecond));
        if (optimum_res_x < x)
            x = optimum_res_x;
        x = Math.round(x);
        x -= x % this.ResXModulus;
        return x;
    }
    
    /*
     * resY();
     *
     * Variable dependencies:
     *  - width
     *  - croppingLeft
     *  - croppingRight
     *  - height
     *  - croppingTop
     *  - croppingBottom
     *  - aspectRatio
     *  - outputFileSize
     *  - videoLength
     *  - audioBitrateModulus
     *  - framesPerSecond
     *  - resXModulus
     *  - resYModulus
     */
    this.resY = function()
    {
        var x = this.Width - this.CroppingLeft - this.CroppingRight;
        var y = this.Height - this.CroppingTop - this.CroppingBottom;
        if (Math.round(this.Width / this.AspectRatio) > this.Height)
            x /= this.Width / Math.round(this.Height * this.AspectRatio)
        else
            y /= this.Height / Math.round(this.Width / this.AspectRatio);
        y = Math.round(this.resX() / (x / y));
        y -= y % this.ResYModulus;
        return y
    }
    
    /*
     * kbps2MB( bitrate, seconds );
     *
     * Convert kbps for a given number of seconds to file size in MB.
     */
    this.kbps2MB = function(bitrate, seconds)
    {
        return bitrate * seconds / 8192;
    }
}

Jeff Mott · 11-25-2003, 06:43 PM

Updated.

Better organized
Follows the naming conventions for OO programming
Includes support for an initial compressibility test

Code:

function DivXVideo()
{
    var videoLength = 0;
    var aspectRatio = 1.7777777777777777777777777777778;
    var width = 720;
    var height = 480;
    var croppingTop = 0;
    var croppingRight = 0;
    var croppingBottom = 0;
    var croppingLeft = 0;
    var framesPerSecond = 23.976023976023976023976023976024;
    var outputFileSize = 703.125;
    var audioBitrateLimit = 128;
    var resXModulus = 4;
    var resYModulus = 2;
    var audioBitrateModulus = 16;
    var qualityFactor = 0.21559718335619570187471422039323;
    
    this.getAudioBitrate = function() {
        var kbps = Math.round(outputFileSize * 8192 / (videoLength * (1 + 780 / audioBitrateLimit)) / audioBitrateModulus) * audioBitrateModulus;
        return kbps > audioBitrateLimit ? audioBitrateLimit : kbps;
    }
    
    this.getVideoBitrate = function() {
        return Math.floor(outputFileSize * 8192 / videoLength) - this.getAudioBitrate();
    }
    
    this.getWidthAfterCrop = function() {
        return width - croppingLeft - croppingRight;
    }
    
    this.getHeightAfterCrop = function() {
        return height - croppingTop - croppingBottom;
    }
    
    this.getResX = function() {
        var x = this.getWidthAfterCrop();
        if (Math.round(width / aspectRatio) > height)
            x /= width / Math.round(height * aspectRatio);
        return Math.round(x);
    }
    
    this.getResXAtModulus = function() {
        var x = Math.round(this.getResX() / resXModulus) * resXModulus;
        x = x > this.getWidthAfterCrop() ? this.getWidthAfterCrop() - this.getWidthAfterCrop() % resXModulus : x;
        while (Math.round(x / (this.getResX() / this.getResY()) / resYModulus) * resYModulus > this.getHeightAfterCrop())
            x -= resXModulus;
        return x;
    }
    
    this.getResY = function() {
        var y = this.getHeightAfterCrop();
        if (Math.round(height * aspectRatio) > width)
            y /= height / Math.round(width / aspectRatio);
        return Math.round(y);
    }
    
    this.getResYAtModulus = function() {
        return Math.round(this.getResXAtModulus() / (this.getResX() / this.getResY()) / resYModulus) * resYModulus;
    }
    
    this.getOptimizedResX = function() {
        var x = Math.round(Math.sqrt(1024 * this.getVideoBitrate() * (this.getResX() / this.getResY()) / (qualityFactor * framesPerSecond)));
        return x > this.getWidthAfterCrop() ? this.getWidthAfterCrop() : x;
    }
    
    this.getOptimizedResXAtModulus = function() {
        var x = Math.round(this.getOptimizedResX() / resXModulus) * resXModulus;
        return x > this.getResXAtModulus() ? this.getResXAtModulus() : x;
    }
    
    this.getOptimizedResY = function() {
        return Math.round(this.getOptimizedResX() / (this.getResX() / this.getResY()));
    }
    
    this.getOptimizedResYAtModulus = function() {
        return Math.round(this.getOptimizedResXAtModulus() / (this.getResX() / this.getResY()) / resYModulus) * resYModulus;
    }
    
    this.getOptimizedQualityFactor = function(bytes) {
        return bytes * 8 / (this.getResXAtModulus() * this.getResYAtModulus() * framesPerSecond * videoLength);
    }
    
    this.getCdCapacity = function(minutes) {
        return minutes * 8.7890625;
    }
    
    this.getVideoLength = function() { return videoLength }
    this.getAspectRatio = function() { return aspectRatio }
    this.getWidth = function() { return width }
    this.getHeight = function() { return height }
    this.getCroppingTop = function() { return croppingTop }
    this.getCroppingRight = function() { return croppingRight }
    this.getCroppingBottom = function() { return croppingBottom }
    this.getCroppingLeft = function() { return croppingLeft }
    this.getFramesPerSecond = function() { return framesPerSecond }
    this.getOutputFileSize = function() { return outputFileSize }
    this.getAudioBitrateLimit = function() { return audioBitrateLimit }
    this.getResXModulus = function() { return resXModulus }
    this.getResYModulus = function() { return resYModulus }
    this.getAudioBitrateMouduls = function() { return audioBitrateModulus }
    this.getQualityFactor = function() { return qualityFactor }
    
    this.setVideoLength = function() {
        if (arguments.length == 3)
            videoLength = 3600 * arguments[0] + 60 * arguments[1] + arguments[2];
        else if (arguments.length == 2)
            videoLength = 60 * arguments[0] + arguments[1];
        else
            videoLength = arguments[0];
    }
    this.setAspectRatio = function(a) { aspectRatio = a }
    this.setWidth = function(w) { width = w }
    this.setHeight = function(h) { height = h }
    this.setCroppingTop = function(c) { croppingTop = c }
    this.setCroppingRight = function(c) { croppingRight = c }
    this.setCroppingBottom = function(c) { croppingBottom = c }
    this.setCroppingLeft = function(c) { croppingLeft = c }
    this.setFramesPerSecond = function(f) { framesPerSecond = f }
    this.setOutputFileSize = function(s) { outputFileSize = s }
    this.setAudioBitrateLimit = function(b) { audioBitrateLimit = b }
    this.setResXModulus = function(m) { resXModulus = m }
    this.setResYModulus = function(m) { resYModulus = m }
    this.setAudioBitrateModulus = function(m) { audioBitrateModulus = m }
    this.setQualityFactor = function(q) { qualityFactor = q }
}

And attached in an HTML document implementing this class.

kwhubby · 12-08-2003, 06:03 AM

Works for moz, not for IE 6. gives the error:
Line: 14
Error: 'DivXVideo' is undefined

Jeff Mott · 12-08-2003, 07:00 AM

I've been using it almost exclusively in IE. Note that the DivXVideo class is not within the HTML doc. The class must be placed within a local DivXVideo.js file, which is then imported into the HTML doc.