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  • audio stream sampling rate in linux

    - by farhan
    Im trying read and store samples from an audio microphone in linux using C/C++. Using PCM ioctls i setup the device to have a certain sampling rate say 10Khz using the SOUND_PCM_WRITE_RATE ioctl etc. The device gets setup correctly and im able to read back from the device after setup using the "read". int got = read(itsFd, b.getDataPtr(), b.sizeBytes()); The problem i have is that after setting the appropriate sampling rate i have a thread that continuously reads from /dev/dsp1 and stores these samples, but the number of samples that i get for 1 second of recording are way off the sampling rate and always orders of magnitude more than the set sampling rate. Any ideas where to begin on figuring out what might be the problem?

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  • Event feed implementation - will it scale?

    - by SlappyTheFish
    Situation: I am currently designing a feed system for a social website whereby each user has a feed of their friends' activities. I have two possible methods how to generate the feeds and I would like to ask which is best in terms of ability to scale. Events from all users are collected in one central database table, event_log. Users are paired as friends in the table friends. The RDBMS we are using is MySQL. Standard method: When a user requests their feed page, the system generates the feed by inner joining event_log with friends. The result is then cached and set to timeout after 5 minutes. Scaling is achieved by varying this timeout. Hypothesised method: A task runs in the background and for each new, unprocessed item in event_log, it creates entries in the database table user_feed pairing that event with all of the users who are friends with the user who initiated the event. One table row pairs one event with one user. The problems with the standard method are well known – what if a lot of people's caches expire at the same time? The solution also does not scale well – the brief is for feeds to update as close to real-time as possible The hypothesised solution in my eyes seems much better; all processing is done offline so no user waits for a page to generate and there are no joins so database tables can be sharded across physical machines. However, if a user has 100,000 friends and creates 20 events in one session, then that results in inserting 2,000,000 rows into the database. Question: The question boils down to two points: Is this worst-case scenario mentioned above problematic, i.e. does table size have an impact on MySQL performance and are there any issues with this mass inserting of data for each event? Is there anything else I have missed?

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  • How to get mouseposition when context menu appears?

    - by ikky
    Hi. I have a panel which holds many pictureboxes. Each picturebox has registered "contextRightMenu" as their context menu. What i want when the context menu pops up is to get the current mouseposition. I have tried getting the mouseposition by using mouseDown and click, but these events happens after one of the items of the context menu is clicked, and that is too late. the popup event of the context menu does not deliver mouse event args, so i don't know how to get the mouseposition. If i can get mouse event args it is easy. Then i just can: this.contextRightClick.Popup += new System.EventHandler(this.contextRightClick_Popup); // If EventArgs include mouseposition within the sender private void contextRightClick_Popup)(object sender, EventArgs e) { int iLocationX = sender.Location.X; int iLocationY = sender.Location.Y; Point pPosition = new Point(iLocationX + e.X, iLocationY + e.Y); // Location + position within the sender = current mouseposition } Can anyone help me either get some mouse event args, or suggest a event that will run before the contextmenu pop ups? Thanks in advance

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  • Handle window scroll event in greasemonkey script

    - by Akim Khalilov
    Hi. I need some advice. I have a web page and want to extend it's functionality with greasemonkey script and firefox. When page has loaded I need run custom function during user's page scrolling (with mouse whell or scrollbar). I want show some div block when user scrolling down and hide it when he scrolling to the top. But I met some problem - I couldn't assign event handler to the onscroll event. I use next part of the code: function showFixedBlock(){ ... } function onScrollStart(){ ... showFixedBlock(); ... } window.onscroll = onScrollStart; I test this piece of code on my test html page and it works, but when I copy it into greasemonkey, script doesn't work. Should I assign onscroll event handler during page loading? As I know greasemonkey execute it's scripts when page has loaded? Is it the reason of the problem? Is there some additional requirments to handle 'onscroll' event? How can I do that? Thanks.

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  • Detecting periodic repetitions in the data stream

    - by pulegium
    Let's say I have an array of zeros: a = numpy.zeros(1000) I then introduce some repetitive 'events': a[range(0, 1000, 30)] = 1 Question is, how do I detect the 'signal' there? Because it's far from the ideal signal if I do the 'regular' FFT I don't get a clear indication of where my 'true' signal is: f = abs(numpy.fft.rfft(a)) Is there a method to detect these repetitions with some degree of certainty? Especially if I have few of those mixed in, for example here: a[range(0, 1000, 30)] = 1 a[range(0, 1000, 110)] = 1 a[range(0, 1000, 48)] = 1 I'd like to get three 'spikes' on the resulting data...

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  • StringBuffer wont read whole stream into a string (JAVA/Android)

    - by Levara
    Hi all! I'm making an android program that retrieves content of a webpage using HttpURLConnection. I'm new to both Java and Android. Problem is: Reader reads whole page source, but in the last while iteration it doesn't append to stringBuffer that last part. Using debbuger I have determined that, in the last loop iteration, string buff is created, but stringBuffer just doesnt append it. I need to parse retrieved content. Is there any better way to handle the content for parsing than using strings. I've read on numerous other sites that string size in Java is limited only by available heap size. I've tried with StringBuilder too. Anyone know what could be the problem. Btw feel free to suggest any improvements to the code. Thanks! URL u; try { u = new URL("http://feeds.timesonline.co.uk/c/32313/f/440134/index.rss"); HttpURLConnection c = (HttpURLConnection) u.openConnection(); c.setRequestProperty("User-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; InfoPath.1; .NET CLR 2.0.50727)"); c.setRequestMethod("GET"); c.setDoOutput(true); c.setReadTimeout(3000); c.connect(); StringBuffer stringBuffer = new StringBuffer(""); InputStream in = c.getInputStream(); InputStreamReader inp = new InputStreamReader(in); BufferedReader reader = new BufferedReader(inp); char[] buffer = new char[3072]; int len1 = 0; while ( (len1 = reader.read(buffer)) != -1 ) { String buff = new String(buffer,0,len1); stringBuffer.append(buff); } String stranica = new String(stringBuffer); c.disconnect(); reader.close(); inp.close(); in.close();

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  • JNI Stream binary data from C++ to Java

    - by Cliff
    I need help passing binary data into Java. I'm trying to use jbytearray but when the data gets into Java it appears corrupt. Can somebody give me a hand? Here's a snip of some example code. First the native C++ side: printf("Building audio array copy\n"); jbyteArray rawAudioCopy = env-NewByteArray(10); jbyte toCopy[10]; printf("Filling audio array copy\n"); char theBytes[10] = {0,1,2,3,4,5,6,7,8,9}; for (int i = 0; i < sizeof(theBytes); i++) { toCopy[i] = theBytes[i]; } env->SetByteArrayRegion(rawAudioCopy,0,10,toCopy); printf("Finding object callback\n"); jmethodID aMethodId = env->GetMethodID(env->GetObjectClass(obj),"handleAudio","([B)V"); if(0==aMethodId) throw MyRuntimeException("Method not found error",99); printf("Invoking the callback\n"); env->CallVoidMethod(obj,aMethodId, &rawAudioCopy); and then the Java callback method: public void handleAudio(byte[] audio){ System.out.println("Audio supplied to Java [" + audio.length + "] bytes"); byte[] expectedAudio = {0,1,2,3,4,5,6,7,8,9}; for (int i = 0; i < audio.length; i++) { if(audio[i]!= expectedAudio[i]) System.err.println("Expected byte " + expectedAudio[i] + " at byte " + i + " but got byte " + audio[i]); else System.out.print('.'); } System.out.println("Audio passed back accordingly!"); } I get the following output when the callback is invoked: library loaded! Audio supplied to Java [-2019659176] bytes Audio passed back accordingly!

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  • "SpeechHypothesized event not raised"

    - by Jankhana
    Hi all, I need to detect the user voice when they pick-up the reciever on the other end. Because Modems usually start playing files (playback terminal) when the first ring goes there. So I planned to use speech recognition when they say "hello", it can start playing the file until wait for playing file. Or even any noise interference it can start speak. I accomplished this with few settings. I found few common words that my engine detects when we speak and the words that comes when it's ringing. It works fine as a stand alone application but if I try to integrate this with my application it just does not raises "SpeechHypothesized" event. I cant understand why this happens. If i see using a break point, the engine is having the delegate assign and invocation property also is initialized properly but than to is doesn't call the event. For calling I'm using C4F tapi manager and for speech recognition i'm using System.Speech library of .Net 3.5. The code for events is as follows : engine.SpeechDetected += new EventHandler<SpeechDetectedEventArgs>(engine_SpeechDetected); engine.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(engine_SpeechRecognized); engine.SpeechHypothesized+=new EventHandler<SpeechHypothesizedEventArgs> (engine_SpeechHypothesized); engine.SpeechRecognitionRejected += new EventHandler<SpeechRecognitionRejectedEventArgs>(engine_SpeechRecognitionRejected); All event's are raised except the speechhypothesized event. Any idea why this happens ????

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  • how to clear the 'double right click ' on google-map-v3..

    - by zjm1126
    this is my code, and I can't remove the mousedown eventlistener : //*********** double right click ********/ var c =0 ; function time(event){ if(event.button == 2){ c++; setTimeout(cc, 600); } if (c >1){ alert('ok i get it') } } //$('#map_canvas')[0].mousedown(time); $('#map_canvas')[0].addEventListener('mousedown', time, false); //$("map_canvas").unbind() //$('map_canvas')[0].onmousedown=function(){};//this can't be clear the event $('map_canvas')[0].removeEventListener('mousedown', time, false); function cc(){ c=0; } //*********** double right click ********/

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  • Multiset of shared_ptrs as a dynamic priority queue: Concept and practice

    - by Sarah
    I was using a vector-based priority queue typedef std::priority_queue< Event, vector< Event >, std::greater< Event > > EventPQ; to manage my Event objects. Now my simulation has to be able to find and delete certain Event objects not at the top of the queue. I'd like to know if my planned work-around can do what I need it to, and if I have the syntax right. I'd also like to know if dramatically better solutions exist. My plan is to make EventPQ a multiset of smart pointers to Event objects: typedef std::multi_set< boost::shared_ptr< Event > > EventPQ; I'm borrowing functions of the Event class from a related post on a multimap priority queue. // Event.h #include <cstdlib> using namespace std; #include <set> #include <boost/shared_ptr.hpp> class Event; typedef std::multi_set< boost::shared_ptr< Event > > EventPQ; class Event { public: Event( double t, int eid, int hid ); ~Event(); void add( EventPQ& q ); void remove(); bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } bool operator > ( const Event & rhs ) const { return ( time > rhs.time ); } double time; int eventID; int hostID; EventPQ* mq; EventPQ::iterator mIt; }; // Event.cpp Event::Event( double t, int eid, int hid ) { time = t; eventID = eid; hostID = hid; } Event::~Event() {} void Event::add( EventPQ& q ) { mq = &q; mIt = q.insert( boost::shared_ptr<Event>(this) ); } void Event::remove() { mq.erase( mIt ); mq = 0; mIt = EventPQ::iterator(); } I was hoping that by making EventPQ a container of pointers, I could avoid wasting time copying Events into the container and avoid accidentally editing the wrong copy. Would it be dramatically easier to store the Events themselves in EventPQ instead? Does it make more sense to remove the time keys from Event objects and use them instead as keys in a multimap? Assuming the current implementation seems okay, my questions are: Do I need to specify how to sort on the pointers, rather than the objects, or does the multiset automatically know to sort on the objects pointed to? If I have a shared_ptr ptr1 to an Event that also has a pointer in the EventPQ container, how do I find and delete the corresponding pointer in EventPQ? Is it enough to .find( ptr1 ), or do I instead have to find by the key (time)? Is the Event::remove() sufficient for removing the pointer in the EventPQ container? There's a small chance multiple events could be created with the same time (obviously implied in the use of multiset). If the find() works on event times, to avoid accidentally deleting the wrong event, I was planning to throw in a further check on eventID and hostID. Does this seem reasonable? (Dumb syntax question) In Event.h, is the declaration of dummy class Event;, then the EventPQ typedef, and then the real class Event declaration appropriate? I'm obviously an inexperienced programmer with very spotty background--this isn't for homework. Would love suggestions and explanations. Please let me know if any part of this is confusing. Thanks.

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  • Sockets: RAW or STREAM

    - by user1415536
    May be the question is a bit stupid, but I'll ask it. I read a lot about raw sockets in network, have seen several examples. So, basically with raw sockets it's possible to build own stack of headers, like stack = IP + TCP/UDP + OWN_HEADER. My question is, is it possible to get some kind of ready frame of first two(IP + TCP/UDP) from the linux kernel and then just append own header to them? The operating system in question is linux and the language is C. I cannot find any function which can do such a thing, but may be I'm digging in a wrong direction.

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  • How to stream a WAV file?

    - by jonasb
    I'm writing an app where I record audio and upload the audio file over the web. In order to speed up the upload I want to start uploading before I've finished recording. The file I'm creating is a WAV file. My plan was to use multiple data chunks. So instead of the normal encoding (RIFF, fmt , data) I’m using (RIFF, fmt , data, data, ..., data). The first issue is that the RIFF header wants the total length of the whole file, but that is of course not known when streaming the audio (I’m now using an arbitrary number). The other problem is that I'm not sure if it's valid since Audacity doesn't recognise the file, and Windows Media Player opens the file but plays only a very small part. I've been reading WAV specs but haven’t found an answer. Any suggestions?

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  • Which namespace does operator<< (stream) go to?

    - by aaa
    If I have have some overloaded ostream operators, defined for library local objects, is its okay for them to go to std namespace? If I do not declare them in std namespace, then I must use using ns:: operator <<. As a possible follow-up question, are there any operators which should go to standard or global namespace?

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  • c# creating a file from input stream

    - by daemonkid
    My component will recieve a pdf file as a filestream from which I will need to create a file. For testing purposes I am trying to read a file using the filestream object and recreate it at a different location. But the recreated file is created blank. the recreated file has the same number of pages though... This is the code StreamReader sr = new StreamReader(_filePath); str = sr.ReadToEnd(); File.WriteAllText(@"C:\recreated.pdf", str); what am I doing wrong? Thanks for your time.

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  • How to stream an HttpResponse with Django

    - by muudscope
    I'm trying to get the 'hello world' of streaming responses working for Django (1.2). I figured out how to use a generator and the yield function. But the response still not streaming. I suspect there's a middleware that's mucking with it -- maybe ETAG calculator? But I'm not sure how to disable it. Can somebody please help? Here's the "hello world" of streaming that I have so far: def stream_response(request): resp = HttpResponse( stream_response_generator()) return resp def stream_response_generator(): for x in range(1,11): yield "%s\n" % x # Returns a chunk of the response to the browser time.sleep(1)

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  • Cannot use fclose on output stream, input stream is fine.

    - by TeeJay
    Whenever I run my program with fclose(outputFile); at the very end, I get an error. glibc detected...corrupted double-linked list The confusing thing about this though, is that I have fclose(inputFile); directly above it and it works fine. Any suggestions? FILE* inputFile = fopen(fileName, "r"); if (inputFile == NULL) { printf("inputFile did not open correctly.\n"); exit(0); } FILE* outputFile = fopen("output.txt", "wb"); if (outputFile == NULL) { printf("outputFile did not open correctly.\n"); exit(0); } /* ... read in inputFile ... */ /* ... some fprintf's to outputFile ... */ fclose(inputFile); fclose(outputFile);

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  • javascript error listener

    - by John Doe
    hi all i try using window.attachEvent (or addEventListener) to capture js errors my callback function gets only one event parameter my question is: how do i get line number and source file of the error from this event? the alternative usage window.onerror=callback; works but an event listener has other benefits thus im giving it a try

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  • Unit Testing an Event Firing From a Thread

    - by Dougc
    I'm having a problem unit testing a class which fires events when a thread starts and finishes. A cut down version of the offending source is as follows: public class ThreadRunner { private bool keepRunning; public event EventHandler Started; public event EventHandler Finished; public void StartThreadTest() { this.keepRunning = true; var thread = new Thread(new ThreadStart(this.LongRunningMethod)); thread.Start(); } public void FinishThreadTest() { this.keepRunning = false; } protected void OnStarted() { if (this.Started != null) this.Started(this, new EventArgs()); } protected void OnFinished() { if (this.Finished != null) this.Finished(this, new EventArgs()); } private void LongRunningMethod() { this.OnStarted(); while (this.keepRunning) Thread.Sleep(100); this.OnFinished(); } } I then have a test to check that the Finished event fires after the LongRunningMethod has finished as follows: [TestClass] public class ThreadRunnerTests { [TestMethod] public void CheckFinishedEventFiresTest() { var threadTest = new ThreadRunner(); bool finished = false; object locker = new object(); threadTest.Finished += delegate(object sender, EventArgs e) { lock (locker) { finished = true; Monitor.Pulse(locker); } }; threadTest.StartThreadTest(); threadTest.FinishThreadTest(); lock (locker) { Monitor.Wait(locker, 1000); Assert.IsTrue(finished); } } } So the idea here being that the test will block for a maximum of one second - or until the Finish event is fired - before checking whether the finished flag is set. Clearly I've done something wrong as sometimes the test will pass, sometimes it won't. Debugging seems very difficult as well as the breakpoints I'd expect to be hit (the OnFinished method, for example) don't always seem to be. I'm assuming this is just my misunderstanding of the way threading works, so hopefully someone can enlighten me.

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  • Async stream writing in a thread

    - by blez
    I have a thread in which I write to 2 streams. The problem is that the thread is blocked until the first one finishes writing (until all data is transferred on the other side of the pipe), and I don't want that. Is there a way to make it asynchronous? chunkOutput is a Dictionary filled with data from multiple threads, so the faster checking for existing keys is, the faster the pipe will write. void ConsumerMethod(object totalChunks) { while(true) { if (chunkOutput.ContainsKey(curChunk)) { if (outputStream != null && chunkOutput[curChunk].Length > 0) { outputStream.Write(chunkOutput[curChunk]); // <-- here it stops } ChunkDownloader.AppendData("outfile.dat", chunkOutput[curChunk], chunkOutput[curChunk].Length); curChunk++; if (curChunk >= (int) totalChunks) return; } Thread.Sleep(10); } }

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  • C#. Saving information about events and event handlers and removing handlers using this information

    - by Philipp
    I have an object which is creating several event handlers using lambda expressions, and I need to remove all handlers created in that object in one time. I'm trying to create some unified static object which will 'know' which handler relates to which object and event if event handler was created through this static object. I tried something like code below, but I don't understand how to save events and event handlers objects, to be able remove handlers in one time. class Program { static void Main(string[] args) { var EventSender = new EventSender(); var EventReceiver = new EventReceiver(EventSender); EventSender.Invoke(" some var "); LinkSaver.RemoveEvent(EventReceiver); // ?? Console.ReadKey(); } } public class ObjLink{ public object Event; public object Action; } public static class LinkSaver { public static void SetEvent<T>(object obj, Action<T> Event, T Action) { Event(Action); var objLink = new ObjLink{Event = Event, Action = Action}; if (!Links.ContainsKey(obj)) Links.Add(obj, new List<ObjLink>{objLink}); else Links[obj].Add(objLink); } static Dictionary<object,List<ObjLink>> Links = new Dictionary<object, List<ObjLink>>(); public static void RemoveEvent(object obj){ foreach(var objLink in Links[obj]){ // objLink.Event -= objLink.Action; ??? } } } public class EventReceiver { public EventReceiver(EventSender obj) { LinkSaver.SetEvent<EventSender.TestDelegate>(this, obj.SetEvent, str => Console.WriteLine(str + " test event!")); } } public class EventSender { public void Invoke(string var) { if (eventTest != null) eventTest(var); } public void SetEvent(TestDelegate Action) { eventTest += Action; } public delegate void TestDelegate(string var); private event TestDelegate eventTest; // by the way public void RemoveFromEvent() { foreach (var handler in eventTest.GetInvocationList()) eventTest -= (TestDelegate)handler; } }

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