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• efficient video format/codec for sparse & binary blob tracking

  - by user391339

  I am working on a blob tracking project and have many high-definition videos that I would like to reduce in size for storage and downstream tracking/shape-analysis. I want to use a lossless method that takes advantage of the black and white nature of the video as well as the fact that not much is moving between individual frames. The videos are quite sparse, with 5 to 10 b&w blobs per frame occupying <30% of the space in total, with each blob moving <5-10% of the field of view between frames and not changing shape too much between 2-3 frames. I will work in Python, Matlab, or LabView for this project, and could use a batch utility if available. It may be worthwhile to export the files as compressed image stacks if a proper video format can't be found. What are the pros and cons of this? A video codec uses correlations between neighboring frames, so it should be more efficient, but not if the wrong one is chosen or if it is improperly configured.

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• How to write a tool, inverting colors in Windows?

  - by vlood

  I read a topic in this site about it, but decided to post another one as I want to write such a tool, but I don't have much experience in C# & .NET, so it could take me too much time just digging the Net, while someone can just direct me to the right library or classes to be used. So, straight to the point. I want to write a tool that, when activated, inverts absolutely all items on the screen and lets you work that way without torturing your eyes with bright light colors. Does anyone have an idea of the needed .NET libraries or third-party frameworks, to implement this? Any help will be greatly appreciated! P.S. Changing to "High Contrast" theme in Windows is not the solution I seek, so please, don't mention it!

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• How can I force a subscriber to be synchronized from a local snapshot?

  - by Brian

  Hello, I have a SQL 2005 server replicating(merge\push) to SQL 2005 and SQL 2000 servers. I have multiple subscribers spread througout the United states. I have set , @snapshot_in_defaultfolder = N'false', @alt_snapshot_folder = N'c:\snapshots\Merge\' (sample location). I take the snapshot from the publisher that is in the same location, 'c:\snapshots\Merge\', and copy it to the subscribers. I wanted to avoid applying the snapshot over the WAN but from the performance I am getting the synchronization is going over the WAN. Does anybody have any ideas how to make sure that I am using the local copy of the snapshot and not the copy at the publisher? Thanks

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• Alter top and bottom borders of Dojo/Dijit Dialog and ContentPane

  - by Joe Zitzelberger

  I have a Dojo/Dijit Dialog that contains a FORM. There is a top border between the title bar and the content, and a bottom border below the content. Both are about 19 or 20 pixels high and colored #eeeeee. I can't find these borders in the CSS anywhere -- actually, neither can the IE Developer Toolbar -- they just don't seem to exist as elements. I suspect that Dijit is adding these programatically. Is there any way to just remove these borders? I just want my content to consume all of the dialog area below the title bar. TIA

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• How to I count key collisions when using boost::unordered_map?

  - by Nikhil

  I have a data structure with 15 unsigned longs, I have defined a hash function using hash_combine as follows: friend std::size_t hash_value(const TUPLE15& given) { std::size_t seed = 0; boost::hash_combine(seed, val1); boost::hash_combine(seed, val2); ... return seed; } I insert a large number of values into a boost::unordered_map but the performance is not good enough. Probably, I could do better with an alternative hashing function. To confirm this, I need to check how many collisions I am getting. How do I do this?

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• Blob ID matching over multiple frames in C++ (image analysis)

  - by pollux

  Dear reader, I'm working on a blob matching and tracking library in C++. Currently I'm using openCV to detect blobs and try to match blobs in a new frame by checking the position, velocity and size of the blob. This works quite okay and I'm receiving a high blob match rate (95% or higher). Sometimes blobs fall out of the image or new blobs appear. Now I need to give matched blobs the same ID as they had before. I'm wondering if there are typical or commonly used techniques for doing this. Or even some keywords I can use to google on. Thanks

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• Jquery Slider PNG black borders IE8

  - by Thomas

  Greetings, I'm having a lot of trouble with the IE8 buy of getting black borders when using a JQUERY slider, with PNG transparent images. Using a slightly modified version of the Nivio slider. I have searched high and low for fixes and blocks of code but so far none have worked. What happens is that as soon as the img cycles it gets the black border and looks like shit (only in IE8). Does anyone know a working fix for this? Or do we just have to ban IE from all computers?

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• Should I Split Tables Relevant to X Module Into Different DB? Mysql

  - by Michael Robinson

  I've inherited a rather large and somewhat messy codebase, and have been tasked with making it faster, less noodly and generally better. Currently we use one big database to hold all data for all aspects of the site. As we need to plan for significant growth in the future, I'm considering splitting tables relevant to specific sections of the site into different databases, so if/when one gets too large for one server I can more easily migrate some user data to different mysql servers while retaining overall integrity. I would still need to use joins on some tables across the new databases. Is this a normal thing to do? Would I incur a performance hit because of this?

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• Accessing php $_SESSION from python (wsgi) - is it possible?

  - by Bill Zimmerman

  Hi, I've got a python/WSGI app which needs to check to see if a user has logged on to a PHP web app. The problem is that the PHP app checks if a user has logged on by comparing a value in the $_SESSION variable to a value in the cookie from the user's browser. I would prefer to avoid changing the behavior of the php app if at all possible. My questions: Is there anyway I can access the session variables from within python? Where should I start to look? Are there any obvious security/performance issues I should be aware of when taking this approach?

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• How to deploy App_Data files with Azure cloud service (web role)

  - by user2977157

  I have a read-only data file (for IP geolocation) that my web role needs to read. It is currently in the App_Data folder, which is NOT included in the deployment package for the cloud service. Unlike "web deploy", there is no checkbox for an azure cloud service deployment to include/exclude App_Data. Is there a reasonable way to get the deployment package to include the App_Data folder/files? Or is using Azure storage for this sort of thing the better way to go? (cost and performance wise) Am using Visual Studio 2013 and the Azure SDK 2.2

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• Tips for measuring the parallelism speed-up in multi-core development.

  - by fnCzar

  I have read many of the good questions and answers around multi-core programming how-tos etc. I am familiar with concurrency, IPC, MPI etc but what I need is advice on how to measure speed-up which will help in making a business case of spending the time to write such code. Please don't answer with "well run it with single-core code then multi-core code and figure out the difference". This is neither a scientific nor a reliable way to measure performance improvement. If you know of tools that will do some of the heavy lifting please mention them. Answers pertaining to methodology will be more fitting but listing tools is ok as well.

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• Use of bit-torrent for large file download as an alternative to FTP

  - by questzen

  The company I work for procures large volumes of data and does this by subscribing to FTP locations. I was wondering if it is possible to download the same using a tracker, the major challenge is authentication of the users IMO. Most ftp servers we subscribe to have a restriction of the number of ftp connection attempts. Does any one here have any experience with this? Any advice is welcome. Edit To clarify, we subscribe to third party vendors and access their ftp location using credentials provided by them. The service is not exclusive to us, they do sell their data to several others. If we could be part of the swarm, the download rates would be pretty high without added penalty. The question is about the possibility of achieving this, so that we can put-forth a proposal in those lines. The vendors obviously wouldn't share data to non-subscribers, so that is a constraint.

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• when to use StringBuilder in java

  - by kostja

  It is supposed to be generally preferable to use a StringBuilder for String concatenation in Java. Is it always the case? What i mean is : Is the overhead of creating a StringBuilder object, calling the append() method and finally toString() smaller then concatenating existing Strings with + for 2 Strings already or is it only advisable for more Strings? If there is such a threshold, what does it depend on (the String length i suppose, but in which way)? And finally - would you trade the readability and conciseness of the + concatenation for the performance of the StringBuilder in smaller cases like 2, 3, 4 Strings?

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• Examples of both beautiful and ugly java code?

  - by tputkonen

  I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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• How to convert value of Generic Type Argument to a concrete type?

  - by Aleksey Bieneman

  I am trying to convert the value of the generic type parameter T value into integer after making sure that T is in fact integer: public class Test { void DoSomething<T>(T value) { var type = typeof(T); if (type == typeof(int)) { int x = (int)value; // Error 167 Cannot convert type 'T' to 'int' int y = (int)(object)value; // works though boxing and unboxing } } } Although it works through boxing and unboxing, this is an additional performance overhead and i was wandering if there's a way to do it directly. Thank you!

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• What is the best way to keep database data encrypted with user passwords?

  - by Dan Sosedoff

  Let's say an application has really specific data which belongs to a user, and nobody is supposed to see it except the owner. I use MySQL database with DataMapper ORM mapper. The application is written in Ruby on Sinatra. Application behavior: User signs up for an account. Creates username and password. Logs into his dashboard. Some fields in specific tables must be protected. Basically, I'm looking for auto-encryption for a model properties. Something like this: class Transaction include DataMapper::Resource property :id, Serial property :value, String, :length => 1024, :encrypted => true ... etc ... belongs_to :user end I assume that encryption/decryption on the fly will cause performance problems, but that's ok. At least if that works - I'm fine. Any ideas how to do this?

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• how to protect an imported win32 dll into a .net application from memory issues

  - by Eric

  I have a c# application that needs to use a legacy win32 dll. The dll is almost its own app, it has dialogs, operations with hardware, etc. When this dll is imported and used, there are a couple of problems that occur: Dragging a dialog (not a windows system dialog, but one created by the dll) across the managed code app causes the UI to not repaint. Further it generates a system out of memory exception from various ui controls. The performance is incredibly slow. There seems to be no way to unload the dll so the memory never gets cleaned up. When we close our managed app, we get another memory exception. At the moment we import each method call as such: [DllImport("dllname.dll", EntryPoint = "MethodName", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]

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• Browser App - RAD UI Development - Is it possible?

  - by Randy Minder

  I've been away from building browser applications for a long time. I'm now interested in creating one for a hobby of mine. I dread having to deal with HTML, JavaScript etc. to build a high quality browser based user interface. I've got the full suite of Telerik controls. Is it possible to build a polished, somewhat feature rich browser UI while being sheltered from the archaic environment of HTML and JavaScript? I'd love to be able to simply drag-drop components, much like building a Win UI and have the exact HTML, JavaScript code created for me. Thanks!

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• How to structure opening hours of a place? May-be there's even an ontology for it?

  - by Ago

  Does anyone know any ontology which specifies opening hours of places? For example, I have a museum, which has 2 seasons. For low season (season start and end is specified), it is opened 10.00 - 18.00 on weekdays and 10-16 on saturday (on sunday it's closed), for high season it's opened 10-20 on weekdays and 10-18 on weekend. If there is no ontology, may-be people have experience, how best to structure information like that? I'm describing information in RDF. But whatever comments are welcome (even if you have relational database which holds given data). Thanks

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• Apache2 on Ubuntu Server w/ CGI, FastCGI, mod_php

  - by illegal3alien

  I've looked at various websites on configuring Apache with cgi and can't get mod_fcgid to work. It works fine using mod_php5, but I wanted to compare performance using cgi and fastcgi. I tried methods using FGCIWrapper among various other techniques and the only one that didn't result in an unlogged 403 or download of the file was using "Action application/x-httpd-php /usr/bin/php-cgi" When trying to configure mod_fcgid the file normally just started a download of an unprocessed file. I used wget to check headers and type was "application/x-httpd-php" At one point I was able to get to the page, but it resulted in a 403, which was listed in access.log, but not error.log (I was told it should be in there too) I tried to get it working on a fresh install of Ubuntu Server 10.04 LTS and 10.10 and had the same results on both, so I'm not doing something correctly in terms of configuration. I tried virtualmin and could only get mod_php to work. The page just prompted a download when selecting cgi or fcgi from the control panel.

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• Does Oracle 11g automatically index fields frequently used for full table scans?

  - by gustafc

  I have an app using an Oracle 11g database. I have a fairly large table (~50k rows) which I query thus: SELECT omg, ponies FROM table WHERE x = 4 Field x was not indexed, I discovered. This query happens a lot, but the thing is that the performance wasn't too bad. Adding an index on x did make the queries approximately twice as fast, which is far less than I expected. On, say, MySQL, it would've made the query ten times faster, at the very least. I'm suspecting Oracle adds some kind of automatic index when it detects that I query a non-indexed field often. Am I correct? I can find nothing even implying this in the docs.

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• Why do so many mathematicians format code so poorly? [closed]

  - by marcog

  I have done a fair amount of programming together with mathematicians. Now I am even teaching some high school kids coming from a mathematics background how to program. Most of these people format their code so hideously it's hard to believe. I've even worked with and taught mathematicians who will fight the auto-indenter! Why is this so common amongst mathematicians? BTW, this is one reason I have started teaching Python. Yet still they find ways other than indentation to produce whacked coding styles!

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• JS Framework that doesn't use CSS selectors?

  - by RoToRa

  A thing that I noticed about most JavaScript frameworks is that the most common way to find/access the DOM elements is to use CSS selectors. However this usually requires the framework to include a CSS selector parser, because they need to support selectors, that the browser natively doesn't, foremost the frameworks own proprietary extensions. I would think that these parsers are large and slow. Wouldn't it be more efficient to have something that doesn't require a parser, such a chained method calls? Some like: id("example").children().class("test").hasAttribute("href") instead of $("#example > .test[href]") Are there any frameworks around that do something like this? And how do they compare with jQuery and friends in regard to performance and size? EDIT: You can consider this a theoretical discussion topic. I don't plan to use anything other than jQuery in any practical projects in near furure. I was just wondering why there aren't any other, possibly better approaches.

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• How do I set font size to 0px in IE6?

  - by Justin808

  I have an unordered list, I'm trying to hide the text in the list. I can do this 2 ways that i know of: font-color: transparent; font-size: 0px; I prefer the 0px method as its not selectable. This issue is neither way works in IE6. The first way just doesn't work in IE6 at all, the 2nd leave a 1PX high font. Is there a way to hide the text in IE6? This is a visual thing, I know you can read the text by reading the source and that is OK, I just need it to visually not be there.

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• how to handle db concurrency in client-server application in C#?

  - by RAJ K

  I am developing an application in C# WPF which will have Client-Server architecture (Client will do products sales billing). I am novice in this area and I asked this question to start my development process. Click here to view question. So, ultimately I have selected MySQl, WCf & WPF. Now I have one silly question. Do i need to handle DB concurrency explicitly in my application (like 3 clients inserting data same time) or MySQl will handle this without any conflict? To accomplish my project i thought, I will create a service in WCf which will do DB queries from client application. Do you have any suggestion to improve my application performance.

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