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  • Reducing moire when downsampling halftone comic images.

    - by drawnonward
    How can I reduce moire effects when downsampling halftone comic book images during live zoom on an iPhone or iPad? I am writing a comic book viewer. It would be nice to provide higher resolution images and allow the user to zoom in while reading the comic book. However, my client is averse to moire effects and will not allow this feature if there are noticeable moire artifacts while zooming, which of course there are. Modifying the images to be less susceptible to moire would only work if the modifications were not perceptible. Blur was specifically prohibited, as is anything that removes the beloved halftone dots. The images are black and white halftone and line art. The originals are 600 dpi but what we ship with the application will be half that at best, so probably 2500 pixels or less tall. So what are my options? If I write a custom downsampling algorithm would it be fast enough for real time on these devices? Are there other tricks I can do? Would it work to just avoid the size ratios that have the most visual moire effects? As you zoom in an out, there are definitely peaks where the moire effects are worst. Is there a way to calculate what those points are and just zoom to a nearby scale that is not as bad? Any suggestions are welcome. I have very little experience with image and signal processing, but am enjoying the opportunity to learn. I know nothing of wavelets and acutance and other jargon, so please be verbose.

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  • Cepstral Analysis for pitch detection

    - by Ohmu
    Hi! I'm looking to extract pitches from a sound signal. Someone on IRC just explain to me how taking a double FFT achieves this. Specifically: take FFT take log of square of absolute value (can be done with lookup table) take another FFT take absolute value I am attempting this using vDSP I can't understand how I didn't come across this technique earlier. I did a lot of hunting and asking questions; several weeks worth. More to the point, I can't understand why I didn't think of it. I am attempting to achieve this with vDSP library. it looks as though it has functions to handle all of these tasks. However, I'm wondering about the accuracy of the final result. I have previously used a technique which scours the frequency bins of a single FFT for local maxima. when it encounters one, it uses a cunning technique (the change in phase since the last FFT) to more accurately place the actual peak within the bin. I am worried that this precision will be lost with this technique I'm presenting here. I guess the technique could be used after the second FFT to get the fundamental accurately. But it kind of looks like the information is lost in step 2. as this is a potentially tricky process, could someone with some experience just look over what I'm doing and check it for sanity? also, I've heard there is an alternative technique involving fitting a quadratic over neighbouring bins. Is this of comparable accuracy? if so, I would favour it, as it doesn't involve remembering bin phases. so questions: does this approach makes sense? Can it be improved? I'm a bit worried about And the log square component; there seems to be a vDSP function to do exactly that: vDSP_vdbcon however, there is no indication it precalculates a log-table -- I assume it doesn't, as the FFT function requires an explicit pre-calculation function to be called and passed into it. and this function doesn't. Is there some danger of harmonics being picked up? is there any cunning way of making vDSP pull out the maxima, biggest first? Can anyone point me towards some research or literature on this technique? the main question: is it accurate enough? Can the accuracy be improved? I have just been told by an expert that the accuracy IS INDEED not sufficient. Is this the end of the line? Pi PS I get SO annoyed (npi) when I want to create tags, but cannot. :| I have suggested to the maintainers that SO keep track of attempted tags, but I'm sure I was ignored. we need tags for vDSP, accelerate framework, cepstral analysis

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  • ubuntu dmidecode is not functioning properly

    - by Alaa Alomari
    dmidecode is giving irrelevant and conflicted results. it shows that i have two slots while the correct is 8 (the board is Tyan S5350.) uname -a Linux synd01 3.0.0-16-server #29-Ubuntu SMP Tue Feb 14 13:08:12 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux root@synd01:/home/badmin# dmidecode -t 16 dmidecode 2.9 SMBIOS 2.33 present. Handle 0x0011, DMI type 16, 15 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: None Maximum Capacity: 4 GB Error Information Handle: Not Provided Number Of Devices: 2 while root@synd01:/home/badmin# dmidecode -t 17 | grep Size Size: No Module Installed Size: No Module Installed Size: 1024 MB Size: 1024 MB Size: No Module Installed Size: No Module Installed Size: 1024 MB Size: 1024 MB also lshw shows: *-memory description: System Memory physical id: 11 slot: System board or motherboard size: 4GiB *-bank:0 description: DIMM DDR Synchronous 166 MHz (6.0 ns) [empty] physical id: 0 slot: J3B1 clock: 166MHz (6.0ns) *-bank:1 description: DIMM DDR Synchronous 166 MHz (6.0 ns) [empty] physical id: 1 slot: J3B3 clock: 166MHz (6.0ns) *-bank:2 description: DIMM DDR Synchronous 166 MHz (6.0 ns) physical id: 2 slot: J2B2 size: 1GiB width: 64 bits clock: 166MHz (6.0ns) *-bank:3 description: DIMM DDR Synchronous 166 MHz (6.0 ns) physical id: 3 slot: J2B4 size: 1GiB width: 64 bits clock: 166MHz (6.0ns) *-bank:4 description: DIMM DDR Synchronous 166 MHz (6.0 ns) [empty] physical id: 4 slot: J3B2 clock: 166MHz (6.0ns) *-bank:5 description: DIMM DDR Synchronous 166 MHz (6.0 ns) [empty] physical id: 5 slot: J2B1 clock: 166MHz (6.0ns) *-bank:6 description: DIMM DDR Synchronous 166 MHz (6.0 ns) physical id: 6 slot: J2B3 size: 1GiB width: 64 bits clock: 166MHz (6.0ns) *-bank:7 description: DIMM DDR Synchronous 166 MHz (6.0 ns) physical id: 7 slot: J1B1 size: 1GiB width: 64 bits clock: 166MHz (6.0ns) what might cause this conflict and how can i fix it? Thanks

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  • Is there a touch-friendly casino gambling (poker, roulette, slot machine) application that interfaces with coin acceptors

    - by Pitto
    Hello everybody... Does anyone have experience with gambling games (roulette, poker and so on) on Ubuntu? I would like to setup a touchscreen kiosk in my home with Ubuntu... Anything that works with coin and cash acceptors, reports payouts, lets the administrator set payout rates and so on Any experiences/hints? I am interested in full statistics / pay tweakings / cash flow analysis... Thanks a lot!

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  • C#: How to force "calling" a method from the main thread by signaling in some way from another thread

    - by Fire-Dragon-DoL
    Sorry for long title, I don't know even the way on how to express the question I'm using a library which run a callback from a different context from the main thread (is a C Library), I created the callback in C# and when gets called I would like to just raise an event. However because I don't know what will be inside the event, I would like to find a way to invoke the method without the problem of locks and so on (otherwise the third party user will have to handle this inside the event, very ugly) Are there any way to do this? I can be totally on the wrong way but I'm thinking about winforms way to handle different threads (the .Invoke thing) Otherwise I can send a message to the message loop of the window, but I don't know a lot about message passing and if I can send "custom" messages like this Example: private uint lgLcdOnConfigureCB(int connection, System.IntPtr pContext) { OnConfigure(EventArgs.Empty); return 0U; } this callback is called from another program which I don't have control over, I would like to run OnConfigure method in the main thread (the one that handles my winform), how to do it? Or in other words, I would like to run OnConfigure without the need of thinking about locks

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  • STFT and ISTFT in Python

    - by endolith
    Is there any form of short-time Fourier transform with corresponding inverse transform built into SciPy or NumPy or whatever? There's the pyplot specgram function in matplotlib, which calls ax.specgram(), which calls mlab.specgram(), which calls _spectral_helper(): #The checks for if y is x are so that we can use the same function to #implement the core of psd(), csd(), and spectrogram() without doing #extra calculations. We return the unaveraged Pxy, freqs, and t. I'm not sure if this can be used to do an STFT and ISTFT, though. Is there anything else, or should I translate something like this?

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  • spike in my inverse fourier transform

    - by Jon
    I am trying to compare two data sets in MATLAB. To do this I need to filter the data sets by Fourier transforming the data, filtering it and then inverse Fourier transforming it. When I inverse Fourier transform the data however I get a spike at either end of the red data set (picture shows the first spike), it should be close to zero at the start, like the blue line. I am comparing many data sets and this only happens occasionally. I have three questions about this phenomenon. First, what may be causing it, secondly, how can I remedy it, and third, will it affect the data further along the time series or just at the beginning and end of the time series as it appears to from the picture. Any help would be great thanks.

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  • Basic image processing question

    - by indoman
    Can you enlarge a feature so that rather than take up a certain number of pixels it actually takes up one or two times that many to make it easier to analyze? Would there be a way to generalize that in MATLAB?

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  • Daubechies-4 Transform in MATLAB

    - by Myx
    Hello: I have a 4x4 matrix which I wish to decompose into 4 frequency bands (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4 wavelet transform. As a result of the transform, each band should contain 2x2 coefficients. How can I do this in MATLAB? I know that MATLAB has dbaux and dbwavf functions. However, I'm not sure how to use them and I also don't have the wavelet toolbox. Any help is greatly appreciated. Thanks.

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  • TMS320C64x Quick start reference for porgrammers

    - by osgx
    Hello Is thare any quickstart guide for programmers for writing DSP-accelerated appliations for TMS320C64x? I have a program with custom algorythm (not the fft, or usial filtering) and I want to accelerate it using multi-DSP coprocessor. So, how should I modify source to move computation from main CPU to DSPs? What limitations are there for DSP-running code? I have some experience with CUDA. In CUDA I should mark every function as being host, device, or entry point for device (kernel). There are also functions to start kernels and to upload/download data to/from GPU. There are also some limitations, for device code, described in CUDA Reference manual. I hope, there is an similar interface and a documentation for DSP.

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  • How get Android 2.1 SDK to recognize new class: SignalStrength

    - by Doughy
    The new Android 2.1 SDK (version 7) has a new class called SignalStrength: http://developer.android.com/reference/android/telephony/SignalStrength.html I updated my SDK in Eclipse to include the 2.1 add-on, and now I am trying to use this new class. However, when I go to do an import android.telephony.SignalStrength, it can't find it. Do I have to somehow reset my project to refresh the SDK so it knows about the new libraries? How can I get it to recognize this new class? Thanks.

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  • Can anyone give me a sample DSP script in C/C++

    - by Andrew
    Im working on a (Audio) DSP project and just wondering if there are any sample (Open source) DSP example that are written in c or c++, for my MSP430 Chip. I just want something as a guideline so i can program my own script using the ACD and DCA on my board for sampling. http://focus.ti.com/docs/toolsw/folders/print/msp-exp430f5438.html Thats my board, MSP430F5438 Experimenter Board, from what i herd it can run dsp script via the USB connection with the computer. Im using CCS ( From TI, code composer studio) and Octave/Matlab. Just any DSP example scripts or sites that will help me create my own would be appreciated. What im tying to do, Partial audio (sampled) track -- Nyquist rate sampling -- over- and undersampling -- reconstruction of the audio track.

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  • Using Cepstrum for PDA

    - by CziX
    Hey, I am currently deleveloping a algorithm to decide wheather or not a frame is voiced or unvoiced. I am trying to use the Cepstrum to discriminate between these two situations. I use MATLAB for my implementation. I have some problems, saying something generally about the frame, but my currently implementation looks like (I'm award of the MATLAB has the function rceps, but this haven't worked for either): ceps = abs(ifft(log10(abs(fft(frame.*window')).^2+eps))); Can anybody give me a small demo, that will convert the frame to the power cepstrum, so a single lollipop at the pitch frequency. For instance use this code to generate the frequency. fs = 8000; timelength = 25e-3; freq = 500; k = 0:1/fs:timelength-(1/fs); s = 0.8*sin(2*pi*freq*k); Thanks.

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  • Simulink sim of rician channel ber process

    - by bob
    Hi, I'm learning simulink and I want to use the rician channle block from the communications blockset. I'm told I need to change the format format. Would anyone have some sample code where they used the rician channels in simulink to model a bit error rate process?

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  • .NET Library to Identify Pitches

    - by Antoni
    I'd like to write a simple program(preferably in C#) to which I sing a pitch using a mic and the program identifies to which musical note that pitch corresponds. Thank you very much for your prompt responses. I clarify: I'd like a (preferably .NET) library that would identify the notes I sing. I'd like that such a library: Identifies a note when I sing(a note from the chromatic scale). Tells me how much I'm off from the closest note. I intend to use such a library to sing one note a time.

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  • Beagleboard: How do I send/receive data to/from the DSP?

    - by snakile
    I have a beagleboard with TMS320C64x+ DSP. I'm working on an image processing beagleboard application. Here's how it's going to work: The ARM reads an image from a file and put the image in a 2D array. The arm sends the matrix to the DSP. The DSP receives the matrix. The DSP performs the image processing algorithm on the received matrix (the algorithm code uses about 5MB of dynamically allocated memory). The DSP sends the processed image (matrix) to the ARM. The arm received the matrix. The arm saved the processed image to a file. I'v already written the code for steps 1,3,5. What is the easiest way to do steps 3+4 (sending the data)? Code examples are welcome.

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  • Using imtophat in Matlab

    - by jaff12
    I'm trying to do top hat filtering in matlab. The imtophat function looks promising, but I have no idea how to use it. I dont have a lot of work with Matlab before. I am trying to look find basically small spots several pixels wide that are local max in my 2 dimensional array.

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  • Convolving two signals

    - by John Elway
    Calculate the convolution of the following signals (your answer will be in the form of an equation): h[n] = delta[n-1] + delta[n+1], x[n] = delta[n-a] + delta[n+b] I'm lost as to what I do with h and x. Do I simply multiply them? h[n]*x[n]? I programmed convolution with several types of blurs and edge detectors, but I don't see how to translate that knowledge to this problem. please help!

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  • What's the fastest way to approximate the period of data using Octave?

    - by John
    I have a set of data that is periodic (but not sinusoidal). I have a set of time values in one vector and a set of amplitudes in a second vector. I'd like to quickly approximate the period of the function. Any suggestions? Specifically, here's my current code. I'd like to approximate the period of the vector x(:,2) against the vector t. Ultimately, I'd like to do this for lots of initial conditions and calculate the period of each and plot the result. function xdot = f (x,t) xdot(1) =x(2); xdot(2) =-sin(x(1)); endfunction x0=[1;1.75]; #eventually, I'd like to try lots of values for x0(2) t = linspace (0, 50, 200); x = lsode ("f", x0, t) plot(x(:,1),x(:,2)); Thank you! John

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  • BlackBerry Technical Specification

    - by Sam
    I'm having trouble locating BlackBerry techical specifications and their website is a mess. They also don't have a number that I can use to easily contact them. This isn't exactly a coding question, but what does the BlackBerry audio API look like, and where can I get technical specifications on audio? Specifically, I'm trying to find out more information on Audio-In, specifically, through the Mic-In on the 3.5 mm jack. Unfortunately, before I can proceed, I need to know such things like sampling rate, data width, etc. Direction to the right resource or if you know off of the top of your head is appreciated.

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