Reading image stream with multiple threads

Hello folks
I thought about a model for an app I need to code and I need your opinion.
My task is to implement an application that does the following:
- Read and decode images from a stream.
- Do some image processing
- Display the resulting images in Swing window.
Since decoding is expensive and i might want to use a multiprocessor machine,
I decided to put the image reading and decoding in a different thread. from the
image processing (and maybe painting).
In the end, I thought about using 2 objects and 3 threads:
- one object that keeps the Swing window data and the image processing logic
- one object that keeps the stream connection data and the decompression logic
for the (jpeg) images
-one thread that waits for incoming events and decodes them. After decompressing
one image, it sends an event to all objects that needs the image data, in this case
this is the object that keeps the image processing logic. Therefore it updates an
image reference in the image processing logics object. The image object only
allow synchronized access by all threads.
-another thread whose logic is inside the image processing logic object takes
the current data from the image reference the first thread writes to via events
and does image processing. The result is written to another image reference within
the same object. After that, it sleeps for 10 ms or so.
-a third thread is triggered via invokeLater by the image processing thread after
it produced a result. It calls the repaint() method of the Swing control which draws
the result-image to the screen.
Do you see any mistakes or do you have better suggestions to do it?
Please let me know!
Thanks in advance!

If the file is on a diskdrive, it's likely that your program will be i/o bound and threads won't help.
Edited by: ChuckBing on Jul 2, 2008 11:32 AM

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Message Edited by for(imstuck) on 03-03-2010 01:13 PM
Message Edited by for(imstuck) on 03-03-2010 01:17 PM
CLA, LabVIEW Versions 2010-2013

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Reading a file with multiple threads?

I have a file that contains some data. In my application, I currently have three worker threads that perform the same long-executing task using three different data sets. They each need to read some data from the same file. Is this a problem as long as they are only reading it? I know it would be if they modified it but I didn't think it was a problem if they were only reading it.
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If the file is on a diskdrive, it's likely that your program will be i/o bound and threads won't help.
Edited by: ChuckBing on Jul 2, 2008 11:32 AM

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Sorry Kglad, I didn't mean to be rude. With "No coding
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Perhaps I didnt explain the situation clearly enough (in part
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Streams with multiple writers

Here is a conundrum I've been unable to solve:
How do multiple threads write to a PrintWriter, and then disconnect without killing each other?
Here's the long version:
Consider a thread with two pipes:
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PipedOutputWriter p1out = new PipedOutputWriter(p1in);For speed, efficiency, and the desire to use the readline() method, this thread wants to wrap the input with a buffer:
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However, when one of those threads exits, all the pipes close and everyone dies.
Say I have another thread that does the following:
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xx = null;And let the thread exit. I'd be wrong, however. It makes everything die. So, what can I do?
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Ok, so here's what I found. First, I had the reader thread export a PrintWriter by doing the following:
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Here's what I found:
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Craziness.
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Please help me with multiple threads

I don't understand much about multiple threads, so can anyone help me with this? can you show me a small simple code about multiple threads?

Do you understand much about google? yahoo?

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Java Thread.1 }
Java Thread.2 }
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Java Thread.n }
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Regards
Arun

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You can have a look at the link here [GOS Contents|http://help-abap.zevolving.com/2009/02/generic-object-services-gos-toolbar-part-5-get-note-attachment-contents/]
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Hello everyone and Happy New Year!
I was hoping someone might be able to shed some light on this problem. I am updating an older application to use multiple threads. Actually the thread that is causing a problem right now is created by using an Asynchronous timer.
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Ed.
Solved!
Go to Solution.

I just tried this using the sample access database that comes with CVI. It uses a DSN instead of mdb. It worked fine though. I don't see any reason multithreading would be a problem here if you are opening and closing the connection in the same code segment. I do notice that you are using params in the asyn callback connection string. Where does this come from? Maybe try using the sample database and see if that works.
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Hello,
First let me give you the premise that I am working under... I am hoping to have multiple receive threads to make sure that I am pulling data off the port as quickly as possible and am hoping to do this efficiently through using asynchronous functions.
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Receive client running...
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Hello Robbie,
>>Can anyone help me figure out why I am getting the right number of continuations from ReceiveAsync with the wrong packets?
Please have a try to use only one thread to read these byte stream as:
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In your original code, there are multi threads seems to result a repeat read behavior.
Regards.
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thoughput.zip ‏1261 KB

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Hi Michael,
820039 wrote:
I am working on a project that uses several bdb databases both btree, and hashmap inside an environment. This system is multithreaded and as such I decided to use the concurrent data storage subsystem to manage the threads. However this doesn't seem to to be working to well.
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Additional Documentation:
The Berkeley DB products - http://download.oracle.com/docs/cd/E17076_01/html/programmer_reference/intro_products.html#id2707424
Berkeley DB Concurrent Data Store Applications - http://download.oracle.com/docs/cd/E17076_01/html/programmer_reference/cam.html
Berkeley DB Transactional Data Store Applications - http://download.oracle.com/docs/cd/E17076_01/html/programmer_reference/transapp.html
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See my comments for things I did different...
import flash.display.Loader;
import flash.utils.ByteArray;
import formatter.Base64;
var imgB64Str:String="";
var ld:Loader=new Loader();
var my_req:URLRequest = new URLRequest("images.img"); // CHANGED: source file, due to new format
var my_loader:URLLoader = new URLLoader();
my_loader.dataFormat = URLLoaderDataFormat.VARIABLES; // CHANGED: formatting input from text to variables
my_loader.addEventListener(Event.COMPLETE, loadText);
my_loader.load(my_req);
function loadText(e:Event):void{
    imgB64Str = my_loader.data.image1; // CHANGED: instead of grabbing whole data, grabbing the image1 variable
    trace(imgB64Str); // CHANGED: traces fine!
    // same as other from here down!
    ld.x = ld.y = 50;
    ld.loadBytes(Base64.Decode(imgB64Str));
    addChild(ld);
It runs with no errors, but the image no longer displays.
What's the deal?!? :/
Any help is greatly appreciated.

See this site: AN EASY REFERENCE FOR OLE AUTOMATION by Serder Simsekler.
Best!
Jim

Reading image stream with multiple threads

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