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• How to do a sample rate conversion in Windows (and OSX)

  - by Paperflyer

  I am about to write an audio file converter for my side job at the university. As part of this I would need sample rate conversion. However, my professor said that it would be pretty hard to write a sample rate converter that was both of good quality and fast. On my research on the subject, I found some functions in the OSX CoreAudio-framework, that could do a sample rate conversion (AudioConverter.h). After all, an OS has to have some facilities to do that for its own audio stack. Do you know a similar method for C/C++ and Windows, that are either part of the OS or open source? I am pretty sure that this function exists within DirectX Audio (XAudio2?), but I seem to be unable to find a reference to it in the MSDN library.

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• Organization &amp; Architecture UNISA Studies &ndash; Chap 5

  - by MarkPearl

  Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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• Beginner SQL question: arithmetic with multiple COUNT(*) results

  - by polygenelubricants

  Continuing with the spirit of using the Stack Exchange Data Explorer to learn SQL, (see: Can we become our own “Northwind” for teaching SQL / databases?), I've decided to try to write a query to answer a simple question (on meta): What % of stackoverflow users have over 10,000 rep?. Here's what I've done: Query#1 SELECT COUNT(*) FROM Users WHERE Users.Reputation >= 10000 Result: 556 Query#2 SELECT COUNT(*) FROM USERS Result: 227691 Now, how do I put them together into one query? What is this query idiom called? What do I need to write so I can get, say, a one-row three-column result like this: 556 227691 0,00244190592

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• questions about multi threading for sockets/tcp-connections.

  - by Fantastic Fourier

  I have a server that connects to multiple clients using TCP/IP connections, using C in Unix. Since it won't have more than 20 connections at a time, I figured I would use a thread per connection/socket. But the problem is writing to the sockets as I'll be sending user prompted msgs to clients. Once each socket is handled by a thread, how do I interact with the created thread to write to the sockets? Should each thread just read from the sockets and I'll write to sockets in the main program? Not sure if that's a good way to go about it.

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• How to use TDD in a not very "Testy" environment

  - by dbemerlin

  I work in a company where OOP is... well, not fobidden, but at least frowned upon as "too complex". My coworkers write lots of 100+ lines functions and they are usually all in a "funcs.inc.php" or "something.inc.php", if they use any functions at all, often they don't since copy-paste is faster. I would love to start using TDD at least for the code i write but as i have to interface with their code i can't see how to begin. It's not legacy code as they are actively developing it and i don't want to modify their code as i don't want to provoke conflicts. Which approach would you suggest, except for changing the company?

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• Databind Parent/Child relation with Mysql

  - by e2k

  What is the best way to databind parent/child relations? Lets say I have two simple objects: Parent with the following properties, ParentId, Name and Childs and Child with the following properties, ChildId, Name and Parent. I want to write a repository using MySql for this but is failing when I bind both Childs and Parent properties, I have only been able to bind either the Childs property of parent or the Parent property och Child or else I would get a infinite loop. Thinking of it the preferable solution would be to only bind this properties when requested. If I use Linq to sql i would be able to write Parent.Childs[0].Parent.Name but how should I accomplish this with my own repository and with MySql, could anyone point me in the right direction? Looking at the Linq 2 sql generated classes they use EntitySet<Child and EntityRef<Parent could this be used with Mysql? I had a thought of using my IChildRepository in the Parent object and let the Public IEnumerable Childs databind the childs but it seems not right? Best regards E2k

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• Unable to save to wincache from cakePHP shell

  - by Phillaf

  I'm trying to retrieve the weather from wunderground.com through their API, and store it in wincache. For testing purposes I made this function in the News model: public function updateWeather(){ $results = file_get_contents('http://api.wunderground.com/api/**api_key**/conditions/q/CA/Montreal.json'); $results = json_decode($results); return Cache::write('weather', $results); } It works fine when I call this from the controller. However, I can't figure why that same function doesn't work when called from the console. I made this shell in order to eventually add this to windows task scheduler. class WeatherShell extends AppShell { public $uses = array('News'); public function main() { $this->News->updateWeather(); } } When running this, I see that $results is correctly populated. I get 'true' from Cache::write(), however, I get 'false' when trying to read. What subtlety am I missing?

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• How do multi-platform games usually store save data?

  - by PixelPerfect3

  I realize this is a bit of a broad question, but I was wondering if there is a "standard" in the industry when it comes to storing save data for games (and is it different across platforms - Xbox/PS/PC/Mac/Android/iOS?) For example for a game like Assassin's Creed or The Walking Dead: They are on multiple platforms and they usually have to save enough information about the player and their actions. Do they use something like XML files, databases, or just straight binary dumps? How much does it differ from platform to platform? I would appreciate it if someone with experience in the game industry would answer this.

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• Control Windows VM from Linux Host

  - by vy32

  I am looking for a tool that will allow me to monitor and control programs running inside a Windows VM from the Linux host machine. I realize that this is similar to what a rootkit would do, and I am completely happy to use some hacker software if it provides the necessary functionality (and if I can get it in source-code form). If I can't find something, I'll have to write it using C. Probably an embedded HTTP server running on an odd port and doing some kind of XMLRPC thing. Here is the basic functionality I need: Get list of running processes Kill a process. Start a process Read/write/create/delete files I would like to: - Read contents of screen - Read all controls on screen. - Send arbitrary click to a Windows control. Does anything like this exist?

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• What are possible reasons for java.io.IOException: "The filename, directory name, or volume label sy

  - by Turismo

  I am trying to copy a file using the following code: File targetFile = new File(targetPath + File.separator + filename); ... targetFile.createNewFile(); fileInputStream = new FileInputStream(fileToCopy); fileOutputStream = new FileOutputStream(targetFile); byte[] buffer = new byte[64*1024]; int i = 0; while((i = fileInputStream.read(buffer)) != -1) { fileOutputStream.write(buffer, 0, i); } For some users the targetFile.createNewFile results in this exception: java.io.IOException: The filename, directory name, or volume label syntax is incorrect at java.io.WinNTFileSystem.createFileExclusively(Native Method) at java.io.File.createNewFile(File.java:850) Filename and directory name seem to be correct. The directory targetPath is even checked for existence before the copy code is executed and the filename looks like this: AB_timestamp.xml The user has write permissions to the targetPath and can copy the file without problems using the OS. As I don't have access to a machine this happens on yet and can't reproduce the problem on my own machine I turn to you for hints on the reason for this exception.

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• Why does update-notifier contains system-crash-notification?

  - by int_ua

  I just had "System Program Problem Detected" window appearing several times before user session even started (I have KDM with autologin to locked session). I traced it with xprop to being /usr/lib/update-notifier/system-crash-notification which is binary (while I expected it to be some script) and belongs to update-notifier package (while I expected it to be somewhere from apport*). P.S. Clicking on Report problem... button didn't do anything. $ dpkg -s update-notifier | grep Version Version: 0.147 $ dpkg -L update-notifier | grep system-crash /usr/lib/update-notifier/system-crash-notification $ grep RELEASE /etc/lsb-release DISTRIB_RELEASE=13.10

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• Accents in file name using Java on Solaris

  - by Stef

  I have a problem where I can't write files with accents in the file name on Solaris. Given following code public static void main(String[] args) { System.out.println("Charset = "+ Charset.defaultCharset().toString()); System.out.println("testéörtkuoë"); FileWriter fw = null; try { fw = new FileWriter("testéörtkuoë"); fw.write("testéörtkuoëéörtkuoë"); fw.close(); I get following output Charset = ISO-8859-1 test??rtkuo? and I get a file called "test??rtkuo?" Based on info I found on StackOverflow, I tried to call the Java app by adding "-Dfile.encoding=UTF-8" at startup. This returns following output Charset = UTF-8 testéörtkuoë But the filename is still "test??rtkuo?" Any help is much appreciated. Stef

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• How to use Mercurial's LargeFiles extension? [migrated]

  - by DuncanBoehle

  I use Mercurial for game development, and I'm trying to use the LargeFiles extension included in Mercurial 2.0 to keep track of large binary assets. Unfortunately there isn't a whole lot of documentation on the extension, so I'm not sure how people are expected to use it. For example, is there any way to safely clean out the .hg/largefiles directory? If I'm on the tip revision, and expect to always have internet access, then I don't need the old versions of largefiles cluttering up the repository, since that's the whole point of using the LargeFiles extension. Also, how do I have more fine-grained control over where the largefile store is? I can only assume that it's created somewhere on the computer that ran hg init, but I have no idea about the details. Thanks!

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• Multiple port asynchronous I/O over serialport in C#

  - by firoso

  I'm trying to write a test application for serial I/O (RS-232) with multiple units in C# and I'm running into an issue with my lack of threading experience so I'm soliciting feedback for a best known method. I've got a pool of COM ports COM1-16 each of which can read/write at any time and I need to be able to manage them simultaneously. Is this a situation for a thread pool? What is some guidance on structuring this applet? Edit: Upon review I was wondering is I really even need to do asynchronous threads here, I could just maintain states for each COM-port and do flow logic (i.e., statemachine) for each COM-port individually.

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• Lucid hangs at booting after kernel upgrade

  - by Thomas Deutsch

  This weekend, one of our servers running Lucid has installed some upgrades: libgcrypt11 1.4.4-5ubuntu2.1 linux-firmware 1.34.14 linux-image-2.6.32-41-generic 2.6.32-41.91 linux-libc-dev 2.6.32-41.91 Afterwards, it rebooted since this was a kernel upgrade. Now, it hangs at booting, after /scripts/init-bottom. init-bottom itself should not be the problem, the last line I can see is "done". So the problem has to be shortly after that. http://manpages.ubuntu.com/manpages/hardy/man8/initramfs-tools.8.html tells me, that the next step is procfs and sysfs are moved to the real rootfs and execution is turned over to the init binary which should now be found in the mounted rootfs. But I don't know how and where. The problem exists with older kernels too, and this one here doesn't fix the problem: http://www.tummy.com/journals/entries/jafo_20111003_160440 Anyone an idea?

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• Nagios suddenly stops working

  - by pankaj sharma

  I have configure passive checks on one my host system for this i am using nsca. it was running fine. suddenly host is showing down on the monitoring. but host was fine and running when i check the logs on the host showing [1347941895] Warning: Attempting to execute the command "/submit_check_result host.example.com 'Current Load' OK 'OK - load average: 0.69, 0.53, 0.42'" resulted in a return code of 127. Make sure the script or binary you are trying to execute actually exists... i restarted nagios services many times but still it is showing the same error. can anyone help me regarding this. thanks in advance..

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• Branchless memory manager?

  - by Richard Fabian

  Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concurrent, in-order CPU, and cache friendly development. Edit: by branchless I mean without doing direct or indirect function calls, and without using ifs. I've been thinking that I can probably implement something that first changes the requested size to zero for false calls, but haven't really got much more than that. I feel that it's not impossible, but the other aspect of this exercise is then profiling it on said "unfriendly" processors to see if it's worth trying as hard as this to avoid branching.

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• Is there a C# open-source search app which scales cheaply?

  - by domspurling

  I need to quickly replace a listings website which has the following characteristics: smallish database (10,000 items, < 1GB) < 10% of the items updated/created/removed daily most common activity is searching the whole dataset, returning 1-1000 items traffic peaks at 1m page impressions per day Scaling strategy for the existing app has been to separate read-only and read/write activity. Multiple slave databases are used for searching and writes are done to a master, which update the slaves using MS SQL replication. Since read activity is more common than write, this has proved to be a cheap way to do database load balancing, without true clustering. I now need to replace the app - are there any C# open-source apps which scale as neatly as this?

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• Routing PHP memcached calls to Oracle Coherence

  - by cj

  A new post Getting Started with the Coherence Memcached Adaptor from David Felcey shows how PHP memcached calls can automatically be routed to store data in Oracle Coherence 12c. This is possible now Coherence 12.1.3 supports Memcached clients using the Binary Memcached protocol. David's post shows how the Coherence Memcached adaptor can be configured as a proxy service that runs in the Coherence cluster. There's nothing particular to configure in the PHP application, except to enable memcached.use_sasl = 1 So what is Coherence? It is an "in-memory data grid solution", with a number of advanced features. You can read more in the Oracle Coherence 12C Data Sheet.

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• Complex relationship between tables in NHibernate

  - by Ilya Kogan

  Hi all, I'm writing a Fluent NHibernate mapping for a legacy Oracle database. The challenge is that the tables have composite primary keys. If I were at total freedom, I would redesign the relationships and auto-generate primary keys, but other applications must write to the same database and read from it, so I cannot do it. These are the two tables I'll focus on: Example data Trips table: 1, 10:00, 11:00 ... 1, 12:00, 15:00 ... 1, 16:00, 19:00 ... 2, 12:00, 13:00 ... 3, 9:00, 18:00 ... Faults table: 1, 13:00 ... 1, 23:00 ... 2, 12:30 ... In this case, vehicle 1 made three trips and has two faults. The first fault happened during the second trip, and the second fault happened while the vehicle was resting. Vehicle 2 had one trip, during which a fault happened. Constraints Trips of the same vehicle never overlap. So the tables have an optional one-to-many relationship, because every fault either happens during a trip or it doesn't. If I wanted to join them in SQL, I would write: select ... from Faults left outer join Trips on Faults.VehicleId = Trips.VehicleId and Faults.FaultTime between Trips.TripStartTime and Trips.TripEndTime and then I'd get a dataset where every fault appears exactly once (one-to-many as I said). Note that there is no Vehicles table, and I don't need one. But I did create a view that contains all VehicleIds from both tables, so I can use it as a junction table. What am I actually looking for? The tables are huge because they cover years of data, and every time I only need to fetch a range of a few hours. So I need a mapping and a criteria that will run something like the following SQL underneath: select ... from Faults left outer join Trips on Faults.VehicleId = Trips.VehicleId and Faults.FaultTime between Trips.TripStartTime and Trips.TripEndTime where Faults.FaultTime between :p0 and :p1 Do you have any ideas how to achieve it? Note 1: Currently the application shouldn't write to the database, so persistence is not a must, although if the mapping supports persistence, it may help at some point in the future. Note 2: I know it's a tough one, so if you give me a great answer, you will be properly rewarded :) Thank you for reading this long question, and now I only hope for the best :)

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• Unit Testing and Code Coverage Frameworks for Objective-C?

  - by Roman Kagan

  I'm planning to write couple applications for iPhone and wonder if there are any Unit Testing and Code Coverage Frameworks for Objective-C?

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• Problem with greek characters using java

  - by Subhendu Mahanta

  I am trying to write greek characters to a file using java like this: String greek = "\u03c1\u03ae\u03bc. \u03c7\u03b1\u03b9\u03c1\u03b5\u03c4\u03ce"; try { BufferedWriter out = new BufferedWriter(new FileWriter("E:\\properties\\outfilename.txt")); out.write(greek); out.close(); } catch (IOException e) { } Not working. Tried to use javac -encoding ISO-8859-7. Also tried java -Dfile.encoding=ISO-8859-7. Assuming that as I do not have greek font in my pc, I downloaded achillies (greek font - Ach4.ttf).Installed it by going to control panel fonts. Any ideas?

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• App Engine webapp.RequestHandler child instances has no self.request during __init__

  - by grucha

  i use modified webapp.RequestHandler for handling requests in my app: class MyRequestHandler(webapp.RequestHandler): """ Request handler with some facilities like user. self.out is the dictionary to pass to templates """ def __init__(self, *args, **kwargs): super(MyRequestHandler, self).__init__(*args, **kwargs) self.out = { 'user': users.get_current_user(), 'logout_url': users.create_logout_url(self.request.uri) } def render(self, template_name): """ Shortcut to render templates """ self.response.out.write(template.render(template_name, self.out)) class DeviceList(MyRequestHandler): def get(self): self.out['devices'] = GPSDevice.all().fetch(1000) self.render('templates/device_list.html') but I get an exception: line 28, in __init__ self.out['logout_url'] = users.create_logout_url(self.request.uri) AttributeError: 'DeviceList' object has no attribute 'request' When the code causing exception is moved out of __init__ everything's fine: class MyRequestHandler(webapp.RequestHandler): """ Request handler with some facilities like user. self.out is the dictionary to pass to templates and initially it contains user object for example """ def __init__(self, *args, **kwargs): super(MyRequestHandler, self).__init__(*args, **kwargs) self.out = { 'user': users.get_current_user(), } def render(self, template_name): """ Shortcut to render templates """ self.out['logout_url'] = users.create_logout_url(self.request.uri) self.response.out.write(template.render(template_name, self.out)) Whi is that? Why there's no self.request after parent's (i.e. webapp.RequestHandler's) __init__ was executed?

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• C# setup project output automatically start with administrative rights

  - by Alex

  Hi, i've created an setup project for a .net-application which works fine. The problem is, that the application begins to write log-files after startup and this requires administrative rights on windows vista and windows 7. I know there are some folders which i could use to write into without administrative rights. When i start the application as administrator, everything works fine. I asked myself, if it's possible to change the setup project in visual studio in a way that the installed application automatically owns administrative rights on the target system? Thanks for every help in advance! Alex

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• Pattern Matching in Scheme

  - by kunjaan

  How do I accept the following input? (list of 0 or more charcters and ends with 3) or (list of 1 or more characters 4 and 0 or more characters after 4) something like (match ( list 3)) -> #t (match ( list 1 2 3)) -> #t (match (list 1 2 3 4)) -> #t (match (list 1 2 3 4 5)) -> #t (match (list 4)) -> #f EDIT: THIS IS NOT MY HOMEWORK. I trying to write something like ELIZA from PAIP but I know only how to write a pattern that begins with a word.

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