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  • Getting Frequency Components with FFT

    - by ruhig brauner
    so I was able to solv my last problem but i stubmled upon the next already. So I want to make a simple spectrogram but in oder to do so I want to understand how FFT-libaries work and what they actually calculate and return. (FFT and Signal Processing is the number 1 topic I will get into as soon as I have time but right now, I only have time for some programming exercises in the evening. ;) ) Here I just summarized the most important parts: int framesPerSecond; int samplesPerSecond; int samplesPerCycle; // right now i want to refresh the spectogram every DoubleFFT_1D fft; WAVReader audioIn; double audioL[], audioR[]; double fftL[], fftR[]; ..... framesPerSecond = 30; audioIn= new WAVReader("Strobe.wav"); int samplesPerSecond = (int)audioIn.GetSampleRate(); samplesPerCycle = (int)(audioIn.GetSampleRate()/framesPerSecond); audioL = new double[samplesPerCycle*2]; audioR = new double[samplesPerCycle*2]; fftL = new double[samplesPerCycle]; fftR = new double[samplesPerCycle]; for(int i = 0; i < samplesPerCycle; i++) { // don't even know why,... fftL[i] = 0; fftR[i] = 0; } fft = new DoubleFFT_1D(samplesPerCycle); ..... for(int i = 0; i < samplesPerCycle; i++) { audioIn.GetStereoSamples(temp); audioL[i]=temp[0]; audioR[i]=temp[1]; } fft.realForwardFull(audioL); //still stereo fft.realForwardFull(audioR); System.out.println("Check"); for(int i = 0; i < samplesPerCycle; i++) { //storing the magnitude in the fftL/R arrays fftL[i] = Math.sqrt(audioL[2*i]*audioL[2*i] + audioL[2*i+1]*audioL[2*i+1]); fftR[i] = Math.sqrt(audioR[2*i]*audioR[2*i] + audioR[2*i+1]*audioR[2*i+1]); } So the question is, if I want to know, what frequencys are in the sampled signal, how do I calculate them? (When I want to print the fftL / fftR arrays, I get some exponential formes at both ends of the array.) Thx :)

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  • C++0x: how to get variadic template parameters without reference?

    - by Sydius
    Given the following contrived (and yes, terrible) example: template<typename... Args> void something(Args... args) { std::tuple<Args...> tuple; // not initializing for sake of example std::get<0>(tuple) = 5; } It works if you call it like so: int x = 10; something<int>(x); However, it does not work if you call it like this: int x = 10; something<int&>(x); Because of the assignment to 5. Assuming that I cannot, for whatever reason, initialize the tuple when it is defined, how might I get this to work when specifying the type as a reference? Specifically, I would like the tuple to be std::tuple<int> even when Args... is int&.

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  • merge three file into one big file

    - by davit-datuashvili
    suppose that we have three array int a[]=new int[]{4,6,8,9,11,12}; int b[]=new int[]{3,5,7,13,14}; int c[]=new int[]{1,2,15,16,17}; and we want to merge it into one big d array where d.length=a.length+b.length+c.length but we have memory problem it means that we must need use only this d array where we should merge these these three array of course we can use merge sort but can we use merge algorithm without sorting method? like two sorted array we can merge in one sorted array what about three or more array?

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  • C++ Memory allocation question involving vectors

    - by TheFuzz
    vector< int > vect; int *int_ptr = new int(10); vect.push_back( *int_ptr ); I under stand that every "new" needs to be followed by a "delete" at some point but does the clear() method clean this memory? What about this method of doing the same thing: vector< int > vect; int int_var = 10; vect.push_back( int_var ); From what I understand, clear() calls the variables destructors, but both vect.push_back() methods in this example push an object on the vector, not a pointer. so does the first example using an int pointer need something other than clear() to clean up memory?

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  • How to do a random-and-unique generator?

    - by javaLearner.java
    I already wrote a random generator which take arguments a and b, where a is minimun and b is maximum value, like this randomGenerator(int a, int b) What I want to do next is: Using a loop, then generate unique number from a to b. Example: I want to have 8 unique numbers, int a = 1; int b = 10; int value; If I do the loop, there is a high % that same number will appear more than once. Any idea how to do it? My own way is: while(int i <= 8){ randomGenerator(a,b); // if value is not in array, then insert into array } I am stuck at the comment part. Is there any way to check if a variable is exists in an array?

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  • Beginner C++ Question

    - by Donal Rafferty
    I have followed the code example here toupper c++ example And implemented it in my own code as follows void CharString::MakeUpper() { char* str[strlen(m_pString)]; int i=0; str[strlen(m_pString)]=m_pString; char* c; while (str[i]) { c=str[i]; putchar (toupper(c)); i++; } } But this gives me the following compiler error CharString.cpp: In member function 'void CharString::MakeUpper()': CharString.cpp:276: error: invalid conversion from 'char*' to 'int' CharString.cpp:276: error: initializing argument 1of 'int toupper(int)' CharString.cpp: In member function 'void CharString::MakeLower()': This is line 276 putchar (toupper(c)); I understand that toupper is looking for int as a parameter and returns an int also, is that the problem? If so how does the example work?

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  • How can I get running totals of integer values from a SortedDictionary?

    - by user578083
    SortedDictionary<int, string> typeDictionary = new SortedDictionary<int, string>(); SortedDictionary<int, int> lengthDictionary = new SortedDictionary<int, int>(); lengthDictionary has values in key value pair as follows: <1,20> <2,8> <3,10> <4,5> i want LINQ query which will return me new list like as follows <1,20> <2,20+8=28> // 20 from key 1 <3,28+10=38> // 28 from key 2 <4,38+5=43> // 38 from key 3 Result should like this: <1,20> <2,28> <3,38> <4,43>

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  • Performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • How to iterate in this query?

    - by Umaid
    for (int I=-1; I<30; I++) { for (int J=0; J<30; J++) { for(int K=1; K<30; K++) { SELECT rowid,Month, Day, Advice from MainCategory where Month= 'May ' and Day in ((cast(strftime('%d',date('now','+(I) day')) as Integer)),(cast(strftime('%d',date('now','+(J) day')) as Integer)),(cast(strftime('%d',date('now','+(K) day')) as Integer))); } } } And for the same reason how to decrement in this query for (int I=-1; I<30; I--) { for (int J=0; J<30; J--) { for(int K=1; K<30; K--) { SELECT rowid,Month, Day, Advice from MainCategory where Month= 'May ' and Day in ((cast(strftime('%d',date('now','(I) day')) as Integer)),(cast(strftime('%d',date('now','(J) day')) as Integer)),(cast(strftime('%d',date('now','(K) day')) as Integer))); } } }

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  • .NET 3.5SP1 64-bit memory model vs. 32-bit memory model

    - by James Dunne
    As I understand it, the .NET memory model on a 32-bit machine guarantees 32-bit word writes and reads to be atomic operations but does not provide this guarantee on 64-bit words. I have written a quick tool to demonstrate this effect on a Windows XP 32-bit OS and am getting results consistent with that memory model description. However, I have taken this same tool's executable and run it on a Windows 7 Enterprise 64-bit OS and am getting wildly different results. Both the machines are identical specs just with different OSes installed. I would have expected that the .NET memory model would guarantee writes and reads to BOTH 32-bit and 64-bit words to be atomic on a 64-bit OS. I find results completely contrary to BOTH assumptions. 32-bit reads and writes are not demonstrated to be atomic on this OS. Can someone explain to me why this fails on a 64-bit OS? Tool code: using System; using System.Threading; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { var th = new Thread(new ThreadStart(RunThread)); var th2 = new Thread(new ThreadStart(RunThread)); int lastRecordedInt = 0; long lastRecordedLong = 0L; th.Start(); th2.Start(); while (!done) { int newIntValue = intValue; long newLongValue = longValue; if (lastRecordedInt > newIntValue) Console.WriteLine("BING(int)! {0} > {1}, {2}", lastRecordedInt, newIntValue, (lastRecordedInt - newIntValue)); if (lastRecordedLong > newLongValue) Console.WriteLine("BING(long)! {0} > {1}, {2}", lastRecordedLong, newLongValue, (lastRecordedLong - newLongValue)); lastRecordedInt = newIntValue; lastRecordedLong = newLongValue; } th.Join(); th2.Join(); Console.WriteLine("{0} =? {2}, {1} =? {3}", intValue, longValue, Int32.MaxValue / 2, (long)Int32.MaxValue + (Int32.MaxValue / 2)); } private static long longValue = Int32.MaxValue; private static int intValue; private static bool done = false; static void RunThread() { for (int i = 0; i < Int32.MaxValue / 4; ++i) { ++longValue; ++intValue; } done = true; } } } Results on Windows XP 32-bit: Windows XP 32-bit Intel Core2 Duo P8700 @ 2.53GHz BING(long)! 2161093208 > 2161092246, 962 BING(long)! 2162448397 > 2161273312, 1175085 BING(long)! 2270110050 > 2270109040, 1010 BING(long)! 2270115061 > 2270110059, 5002 BING(long)! 2558052223 > 2557528157, 524066 BING(long)! 2571660540 > 2571659563, 977 BING(long)! 2646433569 > 2646432557, 1012 BING(long)! 2660841714 > 2660840732, 982 BING(long)! 2661795522 > 2660841715, 953807 BING(long)! 2712855281 > 2712854239, 1042 BING(long)! 2737627472 > 2735210929, 2416543 1025780885 =? 1073741823, 3168207035 =? 3221225470 Notice how BING(int) is never written and demonstrates that 32-bit reads/writes are atomic on this 32-bit OS. Results on Windows 7 Enterprise 64-bit: Windows 7 Enterprise 64-bit Intel Core2 Duo P8700 @ 2.53GHz BING(long)! 2208482159 > 2208121217, 360942 BING(int)! 280292777 > 279704627, 588150 BING(int)! 308158865 > 308131694, 27171 BING(long)! 2549116628 > 2548884894, 231734 BING(int)! 534815527 > 534708027, 107500 BING(int)! 545113548 > 544270063, 843485 BING(long)! 2710030799 > 2709941968, 88831 BING(int)! 668662394 > 667539649, 1122745 1006355562 =? 1073741823, 3154727581 =? 3221225470 Notice that BING(long) AND BING(int) are both displayed! Why are the 32-bit operations failing, let alone the 64-bit ones?

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  • QConnect find no such slot on QCombobox by Qt Creater

    - by user2534154
    I create a window inherit from QWidget I set grid layout to that Window I make a function called handleHeroChange(int index) in public slot inside that window I add a Qcombobox to call that function handleHeroChange(int index). Qtcreator keep telling: QObject::connect: No such slot QWidget::handleHeroChange(int) in ../Testing/Window.cpp:92 Why did i do wrong? THE CODE: Window::Window(QWidget *parent) : QWidget(parent) { QGridLayout *grid = new QGridLayout(this); QComboBox *comboHeroClass = new QComboBox(); comboHeroClass->addItem("Witcher"); comboHeroClass->addItem("Maurander"); comboHeroClass->setCurrentIndex(1); grid->addWidget(comboHeroClass, 2,3,1,1); QComboBox::connect(comboHeroClass, SIGNAL(currentIndexChanged(int)),this, SLOT(handleHeroChange(int))); } void Window::handleHeroChange(int index){ QPixmap myImage; if(index == 0){ }else if(index == 1){ } }

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  • Preon library problem

    - by Kamahire
    I am using preon lib to parse binary data it contain short, int data The structure as follows @BoundNumber(size="32", byteOrder=ByteOrder.BigEndian) public int time;// @BoundString(size="2") public String alphaChar;// 2 byte array @BoundNumber(size="16", byteOrder=ByteOrder.BigEndian) public int code1;//short @BoundNumber(size="16", byteOrder=ByteOrder.BigEndian) public int code2;//short @BoundNumber(size="16", byteOrder=ByteOrder.BigEndian) public int code3;//short @BoundString(size="8") public String firstName;// 8 byte array @BoundString(size="8") public String middleName;// 8 byte array @BoundString(size="8") public String lastName;// 8 byte array @BoundNumber(size="16", byteOrder=ByteOrder.BigEndian) public int code4;//short I am getting correct values for code1, code2, code3 but for code4 it not giving me correct value. It always gives me 0(Zero); When I checked with position of byte array; it shows me correct value. Is there any kind padding require?

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  • 4 table query / join. getting duplicate rows

    - by Horse
    So I have written a query that will grab an order (this is for an ecommerce type site), and from that order id it will get all order items (ecom_order_items), print options (c_print_options) and images (images). The eoi_p_id is currently a foreign key from the images table. This works fine and the query is: SELECT eoi_parentid, eoi_p_id, eoi_po_id, eoi_quantity, i_id, i_parentid, po_name, po_price FROM ecom_order_items, images, c_print_options WHERE eoi_parentid = '1' AND i_id = eoi_p_id AND po_id = eoi_po_id; The above would grab all the stuff I need for order #1 Now to complicate things I added an extra table (ecom_products), which needs to act in a similar way to the images table. The eoi_p_id can also point at a foreign key in this table too. I have added an extra field 'eoi_type' which will either have the value 'image', or 'product'. Now items in the order could be made up of a mix of items from images or ecom_products. Whatever I try it either ends up with too many records, wont actually output any with eoi_type = 'product', and just generally wont work. Any ideas on how to achieve what I am after? Can provide SQL samples if needed? SELECT eoi_id, eoi_parentid, eoi_p_id, eoi_po_id, eoi_po_id_2, eoi_quantity, eoi_type, i_id, i_parentid, po_name, po_price, po_id, ep_id FROM ecom_order_items, images, c_print_options, ecom_products WHERE eoi_parentid = '9' AND i_id = eoi_p_id AND po_id = eoi_po_id The above outputs duplicate rows and doesnt work as expected. Am I going about this the wrong way? Should I have seperate foreign key fields for the eoi_p_id depending it its an image or a product? Should I be using JOINs? Here is a mysql explain of the tables in question ecom_products +-------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+--------------+------+-----+---------+----------------+ | ep_id | int(8) | NO | PRI | NULL | auto_increment | | ep_title | varchar(255) | NO | | NULL | | | ep_link | text | NO | | NULL | | | ep_desc | text | NO | | NULL | | | ep_imgdrop | text | NO | | NULL | | | ep_price | decimal(6,2) | NO | | NULL | | | ep_category | varchar(255) | NO | | NULL | | | ep_hide | tinyint(1) | NO | | 0 | | | ep_featured | tinyint(1) | NO | | 0 | | +-------------+--------------+------+-----+---------+----------------+ ecom_order_items +--------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+----------------+ | eoi_id | int(8) | NO | PRI | NULL | auto_increment | | eoi_parentid | int(8) | NO | | NULL | | | eoi_type | varchar(32) | NO | | NULL | | | eoi_p_id | int(8) | NO | | NULL | | | eoi_po_id | int(8) | NO | | NULL | | | eoi_quantity | int(4) | NO | | NULL | | +--------------+-------------+------+-----+---------+----------------+ c_print_options +------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+---------+----------------+ | po_id | int(8) | NO | PRI | NULL | auto_increment | | po_name | varchar(255) | NO | | NULL | | | po_price | decimal(6,2) | NO | | NULL | | +------------+--------------+------+-----+---------+----------------+ images +--------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+----------------+ | i_id | int(8) | NO | PRI | NULL | auto_increment | | i_filename | varchar(255) | NO | | NULL | | | i_data | longtext | NO | | NULL | | | i_parentid | int(8) | NO | | NULL | | +--------------+--------------+------+-----+---------+----------------+

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  • Why does a non-constant offsetof expression work?

    - by Chris J. Kiick
    Why does this work: #include <sys/types.h> #include <stdio.h> #include <stddef.h> typedef struct x { int a; int b[128]; } x_t; int function(int i) { size_t a; a = offsetof(x_t, b[i]); return a; } int main(int argc, char **argv) { printf("%d\n", function(atoi(argv[1]))); } If I remember the definition of offsetof correctly, it's a compile time construct. Using 'i' as the array index results in a non-constant expression. I don't understand how the compiler can evaluate the expression at compile time. Why isn't this flagged as an error?

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  • C++ performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • Structure within union and bit field

    - by java
    #include <stdio.h> union u { struct st { int i : 4; int j : 4; int k : 4; int l; } st; int i; } u; int main() { u.i = 100; printf("%d, %d, %d", u.i, u.st.i, u.st.l); } I'm trying to figure out the output of program. The first outputs u.i = 100 but I can't understand the output for u.st.i and u.st.l. Please also explain bit fields.

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  • question about in -place sort

    - by davit-datuashvili
    for example we have following array char data[]=new char[]{'A','S','O','R','T','I','N','G','E','X','A','M','P','L','E'}; and index array int a[]=new int[]{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14}: void insitu(char data[],int a[],N){ for (int i=0;i<N;i++) { char v=data[i]; int j,int k; for (k=i;a[k]!=i;k=a[j];a[j]=j) { j=k;data[k]=data[a[k]; } data[k]=v; a[k]=k; } i have question what is initialize value of j? when i run this code it asks me to initialize j and what should do? }

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  • Difficulty understanding behavior of free()

    - by Rasmi Ranjan Nayak
    int main() { int *ptr, **ptr1; ptr = (int*)malloc(sizeof(int)); ptr1 = (int**)malloc(sizeof(int)); free(ptr); *ptr = 12345; ptr1 = &ptr; //free(ptr); //**ptr1 = 23456; printf("%d \n", **ptr1); system("pause"); return 0; } How does *ptr store the value 12345, when the memory has already been freed? So, now ptr should be pointing to garbage. Why is this happening?

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  • Resizing gives me to heavy image

    - by phenevo
    Hi, I'm resizing jpeg 1200x900 ,556kb by method: public static Image ResizeImage(Image imgToResize, int height) //height=400 { int destWidth; int destHeight; int sourceWidth = imgToResize.Width; int sourceHeight = imgToResize.Height; float nPercent = 0; float nPercentH = 0; nPercentH = ((float)height / (float)sourceHeight); nPercent = nPercentH; destWidth = (int)(sourceWidth * nPercent); destHeight = height; Bitmap b = new Bitmap(destWidth, destHeight); Graphics g = Graphics.FromImage((Image)b); g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(imgToResize, 0, 0, destWidth, destHeight); g.Dispose(); return b; } gives me 555kb 533x400 jpeg. Why this photo is so heavy. For photo jpeg 2111kb 2156x1571 I get 556kb 533x400 jpeg Why in first case is so terrible !

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  • C++ inheritance: scoping and visibility of members

    - by Poiuyt
    Can you explain why this is not allowed, #include <stdio.h> class B { private: int a; public: int a; }; int main() { return 0; } while this is? #include <stdio.h> class A { public: int a; }; class B : public A{ private: int a; }; int main() { return 0; } In both the cases, we have one public and one private variable named a in class B. edited now!

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  • How to sort an array by (smallest, largest, second smallest, second, largest) etc?

    - by Binka
    Any ideas? I can sort an array. But not in this pattern? It needs to sort by the pattern I mentioned above. public void wackySort2(int[] nums) { int sign = 0; int temp = 0; int temp2 = 0; for (int i = 0; i < nums.length; i++) { for (int j = 0; j < nums.length - 1; j++) { if (nums[j] > nums[j + 1]) { temp = nums[j]; nums[j] = nums[j + 1]; nums[j + 1] = temp; //sign = 1; System.out.println("Something has been done"); } } } }

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  • Deleting a element from a vector of pointers in C++.

    - by Kranar
    I remember hearing that the following code is not C++ compliant and was hoping someone with much more C++ legalese than me would be able to confirm or deny it. std::vector<int*> intList; intList.push_back(new int(2)); intList.push_back(new int(10)); intList.push_back(new int(17)); for(std::vector<int*>::iterator i = intList.begin(); i != intList.end(); ++i) { delete *i; } intList.clear() The rationale was that it is illegal for a vector to contain pointers to invalid memory. Now obviously my example will compile and it will even work on all compilers I know of, but is it standard compliant C++ or am I supposed to do the following, which I was told is in fact the standard compliant approach: while(!intList.empty()) { int* element = intList.back(); intList.pop_back(); delete element; }

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  • question on revrse array

    - by davit-datuashvili
    we know algorithm how reverse array of n integers for (int i=0;i<n/2;i++){ swap(a[i],a[n-1-i]): } is this method better according the speed of algorithm or not because swap using xor is more fast then in other method here is code public class swap{ public static void main(String[]args){ int a[]=new int[]{2,4,5,7,8,11,13,12,14,24}; System.out.println(" array at the begining:"); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } for (int j=0;j<a.length/2;j++){ a[j]^=a[a.length-1-j]; a[a.length-1-j]^=a[j]; a[j]^=a[a.length-1-j]; } System.out.println("reversed array:"); for (int j=0;j<a.length;j++){ System.out.println(a[j]); } } } //result array at the begining: 2 4 5 7 8 11 13 12 14 24 reversed array: 24 14 12 13 11 8 7 5 4 2

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  • Adding interfaces that won't be actually used

    - by devoured elysium
    I currently have two interfaces(that I'll name here IA and IB): interface IA { int Width; int Height; ... } interface IB { int Width; int Height; ... } that share the same two properties: they both have a Width and a Height property. I was thinking if there is any point in defining an IMatrix interface containing a Width and Height properties: interface IMatrix { int Width; int Height; } The thing is that although they share both the same properties, I won't make use of polymorphism with IMatrix in any of my coding: i.e., there won't by any situation where I'll want to use an IMatrix, I'll just want to use IA and IB. Adding an IMatrix seems more like over-engineering than other thing, but I'd like to ask you guys what your opinion is on the matter. Thanks

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