I would like to speed up sounds in LabVIEW to get chipmunk sounds. It seems to me this would be done by changing the dt for the waveform of the sound, thereby changing the time associated with each Y value, but that seems to have no effect. How is it done? And what does changing dt do?
For reference, my VI is here, I am concerned about the "helium" and "heavy gas" cases.
The trick is in the output configuration of the Sound output VI. That actually controls the generation speed of the output:
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I am new to labview and I need help.
I am using myrio with gyroscope, and when I display the gyroscope values I get noise.
My question is: How can I implement lowpass filter to reduce the noise in X , Y and Z rates of the gyroscope?
I searched a lot, but I did not understand how can I know what is the sampling frequency, the low and the high cutoff frequency.
Thank you so much.
If you're data is noisy you should try to fix the problem before you digitize the data. If a physical low-pass filter will do the trick, install one. The better the signal before the DAQ the better the data will be once it's digitized.
Some other signal conditioning considerations: make sure to reduce the length of wire from the gyroscope to the DAQ to only what's necessary, if possible eliminate any sources of noise from the environment (like any large rotating magnets--seriously I once helped someone who was complaining about noise when they were using an unshielded wire next to an MRI machine), and if you're going to add any signal conditioning try to amplify close to your sensor.
If you still would like to filter in software, there's an example included with LabVIEW that demonstrates both the point-by-point VIs and the array based VIs. It's called PtByBp and Array Based Filter.vi and can be found in the Example Finder under Analysis, Signal Processing and Mathematics >> Filtering and Conditioning
Please install this FREE toolkit from ni.com: http://sine.ni.com/nips/cds/view/p/lang/en/nid/212733
There are examples and good ready to use application how to use myRIO gyroscope and how to do proper DSP.
Sampling frequency is how fast you sample. Look for this value in the ADC settings. Low and high cutoffs - play with those values. Doing an FFT on your signal may help you to determine spectral frequency density, and decide where to cut.
I've written up a variation on Melinda Green's Buddhabrot method for visualizing the Mandelbrot set. Here it is:
http://pastebin.com/RH6dD77F
To create an animation I rendered hundreds of the individual images with slight variations. The variation is a transformation of the coefficients of the generating function as if they were an abstract vector in a space of coefficients. All of that produced incredible structures in the video...
http://www.youtube.com/watch?v=S2uMAvL_5Fo
The problem? As you can tell, the quality on each image is rather low because it takes forever using the method I came up with (the copies I have on my computer are a little better quality, but still look like old reel-to-reel movies). I'm hoping to find a few methods for increasing quality or lowering output time.
Thanks for any suggestions. I would really like to produce more detailed versions of these. Obviously there is much more structure in the graininess of these images.
You can try something like boxcounting, http://imagej.nih.gov/ij/plugins/fraclac/FLHelp/BoxCounting.htm. If buddhabrot is some sort mandelbrot you can skip some empty boxes. You can use a kd-tree like in packing lightmaps to subdivide the surface.
How can I detect sound on the iPhone?
I currently have it somewhat working using the method described in this article http://mobileorchard.com/tutorial-detecting-when-a-user-blows-into-the-mic/
However, as mentioned in that article, in noisy rooms for example, the method won't work.
So in a way, I'm looking for methods that I can use to separate background noise from actual noise intended?
There probably won't be an existing code on the internet, but if someone can point me to the right direction, it would be very appreciated.
Thank you,
Tee
It's definitely not a great solution, but you could determine a baseline amplitude (ambient sound) and trigger your events when you determine that the amplitude is a certain amount greater for a set amount of time.
I am new to CoreAudio, and I would like to output a simple sine wave and square wave with a given frequency and amplitude through the speakers using CA. I don't want to use sound files as I want to synthesize the sound.
What do I need to do this? And can you give me an example or tutorial? Thanks.
There are a number of errors in the previous answer. I, the legendary :-) James McCartney, not James Harkins wrote the sinewavedemo, I also wrote SuperCollider which is what the audiosynth.com website is about. I also now work at Apple on CoreAudio. The sinewavedemo DOES use CoreAudio, since it uses AudioHardware.h from CoreAudio.framework as its way to play the sound.
You should not use the sinewavedemo. It is very old code and it makes dangerous assumptions about the buffer layout of the audio hardware. The easiest way nowadays to play a sound that you are generating is to use the AudioQueue, or to use an output audio unit with a render callback set.
The best and easiest way to do that without files is to prepare a single cycle buffer, containing one cycle of the wave (this is called technically a wavetable)
In the playback function called by CoreAudio thread, fill the output buffer with samples read from the wave buffer.
Note however that you will face two problems very quickly :
- for the sine wave, if the playback frequency is not an integer multiple of the desired sine frequency, you will probably need to implement an interpolator if you want to have a good quality. Using only integer pointers will generate a significant level of harmonic noise.
for the square wave, avoid to just program an array with +1 / -1 values. Such a signal is not bandlimited and will alias a lot. Do not forget that the spectrum of a square wave is virtually infinite!
To get good algorithms for signal generation, take a look to musicdsp.org, that's probably one of the best resource for that
Are you new to audio programming in general? As a starting point i would check out
http://www.audiosynth.com/sinewavedemo.html
This is a minimum osx sinewave implementation by the legendary James Harkins. Note, it doesn't use CoreAudio at all.
If you specifically want to use CoreAudio for your sinewave you need to create an output unit (RemoteIO on the iphone, AUHAL on osx) and supply an input callback, where you can pretty much use the code from the above example. Check out
http://developer.apple.com/mac/library/technotes/tn2002/tn2091.html
The benefits of CoreAudio are chiefly, chain other effects with your sinewave, write plugins for hosts like Logic & provide the interfaces for them, write a host (like Logic) for plugins that can be chained together.
If you don't wont to write a plugin, or host plugins then CoreAudio might not actually be for you. But one of the best things about using CoreAudio is that once you get your sinewave callback working it is easy to add effects, or mix multiple sines together
To do this you need to put your output unit in a graph, to which you can effects, mixers, etc.
Here is some help on setting up graphs http://timbolstad.com/2010/03/16/core-audio-getting-started-pt2/
It isn't as difficult as it looks. Apple provides C++ helper classes for many things (/Developer/Examples/CoreAudio/PublicUtility) and even if you don't want to use C++ (you don't have to!) they can be a useful guide to the CoreAudio API.
If you are not doing this realtime, using the sin() function from math.h is not a bad idea. Just fill however many samples you need with sin() beforehand when it is time to play it, just send it to the audio buffer. sin() can be quite slow to call once every sample if you are doing this realtime, using an interpolated wavetable lookup method is much faster, but the resulting sound will not be as spectrally pure.
There is a good and well documented sine wave player code example in Chapter 7 of the Adamson/Avila "Learning Core Audio" book, published by Addison-Wesley Professional (ISBN-10: 0-321-63684-8 ):
http://www.informit.com/store/learning-core-audio-a-hands-on-guide-to-audio-programming-9780321636843
It is a rather new publication (2012) and addresses precisely the issue of this question. It's only a starting point, but it's a valuable starting point.
BTW. Don't jump to graphs before having this basic lesson (which involves some math) behind.
Concerning example code, a quick and efficient method I often use deals with a pre-filled sinewave lookup table which has as many members as sample rate, for 44100 Hz the table has size of 44100. In other words, cycle length equals sample rate. This gives an acceptable trade-off between speed and quality in many cases. You can initialize it with the program.
If you generate floating point samples (which is default in OSX), and use math functions, use sinf() rather than (float)sin(). Promotions in inner loop cycles of a render callback are always resource-expensive. So are repetitive multiplications of constants, such as 2.0*M_PI, which can too often be found in code examples.
Initial tests indicate that GDI+ (writing in VB.NET) is not fast enough for my purposes. My application needs to be able to draw tens of thousands of particles (coloured circles, very preferably anti-aliased) in a full screen resolution at 20+ frames per second.
I'm hesitant to step away from GDI+ since I also require many of the other advanced drawing features (dash patterns, images, text, paths, fills) of GDI+.
Looking for good advice about using OpenGL, DirectX or other platforms to speed up particle rendering from within VB.NET. My app is strictly 2D.
Goodwill,
David
If you want to use VB.NET, then you can go with XNA or SlimDX.
I have some experience in creating games with GDI+ and XNA, and I can understand that GDI+ is giving you trouble.
If I where you I'd check out XNA, it's much faster than GDI+ because it actually uses your video card for drawing and it has a lot of good documentation and examples online.
SlimDX also looks good but I don't have any experience with it. SlimDX is basically the DirectX API for .NET.
The only way to get the speed you need is to move away from software rendering to hardware rendering... and unfortunately that does mean moving to OpenGL or DirectX.
The alternative is to try and optimise your graphics routines to only draw the particles that need to be drawn, not the whole screen/window.
I would agree with JaredPar that you're better off profiling first to determine if your existing codebase can be improved before making a huge switch to a new framework. DirectX is not the easiest framework if you're unfamiliar with it.
The most significant speed increase I found, when writing a game maker with GDI+, was to convert my bitmaps to Format32bppPArgb;-
SuperFastBitmap = ConvertImagePixelFormat(SlowBitmap, Imaging.PixelFormat.Format32bppPArgb)
If they are not in this format already, you'll see the difference immediately when you convert.
It's possible the problem is in your algorithm and not GDI+. Profiling is the only way to know for sure. Without a profile it's very possible you will switch to a new GUI framework and hit the exact same problems.
If you did profile, what part of GDI+ was causing a problem?
As Jared said,
it could be that a significant fraction of your cycles are not going into GDI, and you might be able to reduce those.
A simple way to find those is to halt it at random a few times and examine the stack. The chance that you will catch it in the act of wasting time is equal to the fraction of time being wasted.
Any instruction or call instruction that appears on more than one such sample is something that, if you could replace it, you would see a speedup.
In general, the method is this.
As you're working in VB.net, have you tried using WPF (Part of .net since 3.0)? As WPF is based on DirectX rather than GDI+, that should give you the speed you need, although developing WPF is not straight-forward at all.
Because the GDI+ is not moved by the graphics card, it's slow to render because it uses the CPU to render. At least, you can use DirectX or SlimDX.
(sorry for bad english)
See This: http://msdn.microsoft.com/en-us/library/windows/desktop/ff729480%28v=vs.85%29.aspx
http://www.codeproject.com/Articles/159586/Starting-DirectX-with-Visual-Basic-NET