The source code

    /*
    	Speed Plug-in

    	Features:
    		*Adds several properties to the 'file' object indicated upload speed, time left, upload time, etc.
    			- currentSpeed -- String indicating the upload speed, bytes per second
    			- averageSpeed -- Overall average upload speed, bytes per second
    			- movingAverageSpeed -- Speed over averaged over the last several measurements, bytes per second
    			- timeRemaining -- Estimated remaining upload time in seconds
    			- timeElapsed -- Number of seconds passed for this upload
    			- percentUploaded -- Percentage of the file uploaded (0 to 100)
    			- sizeUploaded -- Formatted size uploaded so far, bytes

    		*Adds setting 'moving_average_history_size' for defining the window size used to calculate the moving average speed.

    		*Adds several Formatting functions for formatting that values provided on the file object.
    			- SWFUpload.speed.formatBPS(bps) -- outputs string formatted in the best units (Gbps, Mbps, Kbps, bps)
    			- SWFUpload.speed.formatTime(seconds) -- outputs string formatted in the best units (x Hr y M z S)
    			- SWFUpload.speed.formatSize(bytes) -- outputs string formatted in the best units (w GB x MB y KB z B )
    			- SWFUpload.speed.formatPercent(percent) -- outputs string formatted with a percent sign (x.xx %)
    			- SWFUpload.speed.formatUnits(baseNumber, divisionArray, unitLabelArray, fractionalBoolean)
    				- Formats a number using the division array to determine how to apply the labels in the Label Array
    				- factionalBoolean indicates whether the number should be returned as a single fractional number with a unit (speed)
    				    or as several numbers labeled with units (time)
    	*/

    var SWFUpload;
    if (typeof(SWFUpload) === "function") {
    	SWFUpload.speed = {};

    	SWFUpload.prototype.initSettings = (function (oldInitSettings) {
    		return function () {
    			if (typeof(oldInitSettings) === "function") {
    				oldInitSettings.call(this);
    			}

    			this.ensureDefault = function (settingName, defaultValue) {
    				this.settings[settingName] = (this.settings[settingName] == undefined) ? defaultValue : this.settings[settingName];
    			};

    			// List used to keep the speed stats for the files we are tracking
    			this.fileSpeedStats = {};
    			this.speedSettings = {};

    			this.ensureDefault("moving_average_history_size", "10");

    			this.speedSettings.user_file_queued_handler = this.settings.file_queued_handler;
    			this.speedSettings.user_file_queue_error_handler = this.settings.file_queue_error_handler;
    			this.speedSettings.user_upload_start_handler = this.settings.upload_start_handler;
    			this.speedSettings.user_upload_error_handler = this.settings.upload_error_handler;
    			this.speedSettings.user_upload_progress_handler = this.settings.upload_progress_handler;
    			this.speedSettings.user_upload_success_handler = this.settings.upload_success_handler;
    			this.speedSettings.user_upload_complete_handler = this.settings.upload_complete_handler;

    			this.settings.file_queued_handler = SWFUpload.speed.fileQueuedHandler;
    			this.settings.file_queue_error_handler = SWFUpload.speed.fileQueueErrorHandler;
    			this.settings.upload_start_handler = SWFUpload.speed.uploadStartHandler;
    			this.settings.upload_error_handler = SWFUpload.speed.uploadErrorHandler;
    			this.settings.upload_progress_handler = SWFUpload.speed.uploadProgressHandler;
    			this.settings.upload_success_handler = SWFUpload.speed.uploadSuccessHandler;
    			this.settings.upload_complete_handler = SWFUpload.speed.uploadCompleteHandler;

    			delete this.ensureDefault;
    		};
    	})(SWFUpload.prototype.initSettings);

    	SWFUpload.speed.fileQueuedHandler = function (file) {
    		if (typeof this.speedSettings.user_file_queued_handler === "function") {
    			file = SWFUpload.speed.extendFile(file);

    			return this.speedSettings.user_file_queued_handler.call(this, file);
    		}
    	};

    	SWFUpload.speed.fileQueueErrorHandler = function (file, errorCode, message) {
    		if (typeof this.speedSettings.user_file_queue_error_handler === "function") {
    			file = SWFUpload.speed.extendFile(file);

    			return this.speedSettings.user_file_queue_error_handler.call(this, file, errorCode, message);
    		}
    	};

    	SWFUpload.speed.uploadStartHandler = function (file) {
    		if (typeof this.speedSettings.user_upload_start_handler === "function") {
    			file = SWFUpload.speed.extendFile(file, this.fileSpeedStats);
    			return this.speedSettings.user_upload_start_handler.call(this, file);
    		}
    	};

    	SWFUpload.speed.uploadErrorHandler = function (file, errorCode, message) {
    		file = SWFUpload.speed.extendFile(file, this.fileSpeedStats);
    		SWFUpload.speed.removeTracking(file, this.fileSpeedStats);

    		if (typeof this.speedSettings.user_upload_error_handler === "function") {
    			return this.speedSettings.user_upload_error_handler.call(this, file, errorCode, message);
    		}
    	};
    	SWFUpload.speed.uploadProgressHandler = function (file, bytesComplete, bytesTotal) {
    		this.updateTracking(file, bytesComplete);
    		file = SWFUpload.speed.extendFile(file, this.fileSpeedStats);

    		if (typeof this.speedSettings.user_upload_progress_handler === "function") {
    			return this.speedSettings.user_upload_progress_handler.call(this, file, bytesComplete, bytesTotal);
    		}
    	};

    	SWFUpload.speed.uploadSuccessHandler = function (file, serverData) {
    		if (typeof this.speedSettings.user_upload_success_handler === "function") {
    			file = SWFUpload.speed.extendFile(file, this.fileSpeedStats);
    			return this.speedSettings.user_upload_success_handler.call(this, file, serverData);
    		}
    	};
    	SWFUpload.speed.uploadCompleteHandler = function (file) {
    		file = SWFUpload.speed.extendFile(file, this.fileSpeedStats);
    		SWFUpload.speed.removeTracking(file, this.fileSpeedStats);

    		if (typeof this.speedSettings.user_upload_complete_handler === "function") {
    			return this.speedSettings.user_upload_complete_handler.call(this, file);
    		}
    	};

    	// Private: extends the file object with the speed plugin values
    	SWFUpload.speed.extendFile = function (file, trackingList) {
    		var tracking;

    		if (trackingList) {
    			tracking = trackingList[file.id];
    		}

    		if (tracking) {
    			file.currentSpeed = tracking.currentSpeed;
    			file.averageSpeed = tracking.averageSpeed;
    			file.movingAverageSpeed = tracking.movingAverageSpeed;
    			file.timeRemaining = tracking.timeRemaining;
    			file.timeElapsed = tracking.timeElapsed;
    			file.percentUploaded = tracking.percentUploaded;
    			file.sizeUploaded = tracking.bytesUploaded;

    		} else {
    			file.currentSpeed = 0;
    			file.averageSpeed = 0;
    			file.movingAverageSpeed = 0;
    			file.timeRemaining = 0;
    			file.timeElapsed = 0;
    			file.percentUploaded = 0;
    			file.sizeUploaded = 0;
    		}

    		return file;
    	};

    	// Private: Updates the speed tracking object, or creates it if necessary
    	SWFUpload.prototype.updateTracking = function (file, bytesUploaded) {
    		var tracking = this.fileSpeedStats[file.id];
    		if (!tracking) {
    			this.fileSpeedStats[file.id] = tracking = {};
    		}

    		// Sanity check inputs
    		bytesUploaded = bytesUploaded || tracking.bytesUploaded || 0;
    		if (bytesUploaded < 0) {
    			bytesUploaded = 0;
    		}
    		if (bytesUploaded > file.size) {
    			bytesUploaded = file.size;
    		}

    		var tickTime = (new Date()).getTime();
    		if (!tracking.startTime) {
    			tracking.startTime = (new Date()).getTime();
    			tracking.lastTime = tracking.startTime;
    			tracking.currentSpeed = 0;
    			tracking.averageSpeed = 0;
    			tracking.movingAverageSpeed = 0;
    			tracking.movingAverageHistory = [];
    			tracking.timeRemaining = 0;
    			tracking.timeElapsed = 0;
    			tracking.percentUploaded = bytesUploaded / file.size;
    			tracking.bytesUploaded = bytesUploaded;
    		} else if (tracking.startTime > tickTime) {
    			this.debug("When backwards in time");
    		} else {
    			// Get time and deltas
    			var now = (new Date()).getTime();
    			var lastTime = tracking.lastTime;
    			var deltaTime = now - lastTime;
    			var deltaBytes = bytesUploaded - tracking.bytesUploaded;

    			if (deltaBytes === 0 || deltaTime === 0) {
    				return tracking;
    			}

    			// Update tracking object
    			tracking.lastTime = now;
    			tracking.bytesUploaded = bytesUploaded;

    			// Calculate speeds
    			tracking.currentSpeed = (deltaBytes * 8 ) / (deltaTime / 1000);
    			tracking.averageSpeed = (tracking.bytesUploaded * 8) / ((now - tracking.startTime) / 1000);

    			// Calculate moving average
    			tracking.movingAverageHistory.push(tracking.currentSpeed);
    			if (tracking.movingAverageHistory.length > this.settings.moving_average_history_size) {
    				tracking.movingAverageHistory.shift();
    			}

    			tracking.movingAverageSpeed = SWFUpload.speed.calculateMovingAverage(tracking.movingAverageHistory);

    			// Update times
    			tracking.timeRemaining = (file.size - tracking.bytesUploaded) * 8 / tracking.movingAverageSpeed;
    			tracking.timeElapsed = (now - tracking.startTime) / 1000;

    			// Update percent
    			tracking.percentUploaded = (tracking.bytesUploaded / file.size * 100);
    		}

    		return tracking;
    	};
    	SWFUpload.speed.removeTracking = function (file, trackingList) {
    		try {
    			trackingList[file.id] = null;
    			delete trackingList[file.id];
    		} catch (ex) {
    		}
    	};

    	SWFUpload.speed.formatUnits = function (baseNumber, unitDivisors, unitLabels, singleFractional) {
    		var i, unit, unitDivisor, unitLabel;

    		if (baseNumber === 0) {
    			return "0 " + unitLabels[unitLabels.length - 1];
    		}

    		if (singleFractional) {
    			unit = baseNumber;
    			unitLabel = unitLabels.length >= unitDivisors.length ? unitLabels[unitDivisors.length - 1] : "";
    			for (i = 0; i < unitDivisors.length; i++) {
    				if (baseNumber >= unitDivisors[i]) {
    					unit = (baseNumber / unitDivisors[i]).toFixed(2);
    					unitLabel = unitLabels.length >= i ? " " + unitLabels[i] : "";
    					break;
    				}
    			}

    			return unit + unitLabel;
    		} else {
    			var formattedStrings = [];
    			var remainder = baseNumber;

    			for (i = 0; i < unitDivisors.length; i++) {
    				unitDivisor = unitDivisors[i];
    				unitLabel = unitLabels.length > i ? " " + unitLabels[i] : "";

    				unit = remainder / unitDivisor;
    				if (i < unitDivisors.length -1) {
    					unit = Math.floor(unit);
    				} else {
    					unit = unit.toFixed(2);
    				}
    				if (unit > 0) {
    					remainder = remainder % unitDivisor;

    					formattedStrings.push(unit + unitLabel);
    				}
    			}

    			return formattedStrings.join(" ");
    		}
    	};

    	SWFUpload.speed.formatBPS = function (baseNumber) {
    		var bpsUnits = [1073741824, 1048576, 1024, 1], bpsUnitLabels = ["Gbps", "Mbps", "Kbps", "bps"];
    		return SWFUpload.speed.formatUnits(baseNumber, bpsUnits, bpsUnitLabels, true);

    	};
    	SWFUpload.speed.formatTime = function (baseNumber) {
    		var timeUnits = [86400, 3600, 60, 1], timeUnitLabels = ["d", "h", "m", "s"];
    		return SWFUpload.speed.formatUnits(baseNumber, timeUnits, timeUnitLabels, false);

    	};
    	SWFUpload.speed.formatBytes = function (baseNumber) {
    		var sizeUnits = [1073741824, 1048576, 1024, 1], sizeUnitLabels = ["GB", "MB", "KB", "bytes"];
    		return SWFUpload.speed.formatUnits(baseNumber, sizeUnits, sizeUnitLabels, true);

    	};
    	SWFUpload.speed.formatPercent = function (baseNumber) {
    		return baseNumber.toFixed(2) + " %";
    	};

    	SWFUpload.speed.calculateMovingAverage = function (history) {
    		var vals = [], size, sum = 0.0, mean = 0.0, varianceTemp = 0.0, variance = 0.0, standardDev = 0.0;
    		var i;
    		var mSum = 0, mCount = 0;

    		size = history.length;

    		// Check for sufficient data
    		if (size >= 8) {
    			// Clone the array and Calculate sum of the values
    			for (i = 0; i < size; i++) {
    				vals[i] = history[i];
    				sum += vals[i];
    			}

    			mean = sum / size;

    			// Calculate variance for the set
    			for (i = 0; i < size; i++) {
    				varianceTemp += Math.pow((vals[i] - mean), 2);
    			}

    			variance = varianceTemp / size;
    			standardDev = Math.sqrt(variance);

    			//Standardize the Data
    			for (i = 0; i < size; i++) {
    				vals[i] = (vals[i] - mean) / standardDev;
    			}

    			// Calculate the average excluding outliers
    			var deviationRange = 2.0;
    			for (i = 0; i < size; i++) {

    				if (vals[i] <= deviationRange && vals[i] >= -deviationRange) {
    					mCount++;
    					mSum += history[i];
    				}
    			}

    		} else {
    			// Calculate the average (not enough data points to remove outliers)
    			mCount = size;
    			for (i = 0; i < size; i++) {
    				mSum += history[i];
    			}
    		}

    		return mSum / mCount;
    	};

    }