I'm programming a Steinberg VST-Plugin in XCode 4.6.
I've already implemented a Highpass-filter which works correctly. Now I'm trying to do some nonlinear distortion with a quadratic function. After I implemented the few lines below and loaded the plugin into the host, I get immediatly an Output from the plugin - you can hear nothing, but the meter is up high.
I really can't imagine why. The processReplacing function where the math takes place should only be called when playing sound, not when the plugin is loaded. When I remove the few lines of code below, everything is okay and sounds right, so I assume it has nothing to do with the rest of the plugin-code.
The problem takes place in two hosts, so its probably not a VST-bug.
Has anybody ever experienced a similar problem?
Many Thanks,
Fabian
void Exciter::processReplacing(float** inputs, float** outputs, VstInt32 sampleFrames){
for(int i = 0; i < sampleFrames; i++) {
tempsample = inputs[0][i];
//Exciter - Transformation in positive region, quadratic distortion and backscaling
tempsample = tempsample + 1.0f;
tempsample = powf(tempsample, 2.0f);
tempsample = tempsample / 2.0f;
tempsample -= 1.0f;
//Mix-Knob: Dry/Wet ------------------------------------------------
outputs[0][i] = mix*(tempsample) + (1-mix)*inputs[0][i];
EDIT: I added logfile-outputs to each function and it occurs, that the processReplacing function is called permanently, not only when playback is turned on ... But why?
You pretty much answered the question yourself with your edit. processReplacing is called repeatedly. This is part of the VST specification.
VST plug-ins are targeted for real time effects processing. Don't confuse or misinterpret this as lookahead. By real time, I mean inserting the plug-in into a channel and playing an instrument while the DAW is recording. So you can see that in order to mitigate latency, the host is always sending the plug-in an audio buffer (whether it's silence or not).
Related
I have a PID controller working in simulink, but I want to pass it to C++ code. I found how to make a PID with code, something like this:
error = input - refeed;
iError += error * sampleTime;
dError = (error - lastError)/ sampleTime;
//PID Function
output = Kp * error + Ki * iError + Kd * dError;
refeed = output;
lastError = error;
But, that's the only clear thing I got in my research.
I need to know what's the next step, I have the transfer function discretized but I'm not sure about what should I do with the "z" parameters, the times, ...
Is it possible to pass manually a PID controller to C++? How?
The Temperature Control Lab passes a PID output from Python to an Arduino that runs C++ code through a serial USB interface. It is easier to plot values with Python than C++ if you can create an interface for your application. GitHub source code is here.
For the digital control systems, you need to sample the data and execute the controller at every sampling time. z-transform converts the continuous system to the discrete system.
For exampl, if your sampling time is '1', you can express a simple time-series model as below,
y(t) = a1*u(t-1) + a2*u(t-2)
--> y(t) = a1*z^-1*u(t) + a2*z^-2*u(t)
--> y(t) = A(z)u(t), where A(z) = a1*z^-1 + a2*z^-2
a1, a2 = FIR coefficients
However, this time-shift operator 'z^-1' does not appear in your code. It is implicitly expressed with your sampling-time and FOR or DO loop depending on the language that you are using.
Please see the python code for velocity form of PID controller. Velocity form is a little bit easier to implement because you don't worry about the additional logic for the anti-reset windup.
for i in range(1, ns): #ns = simulation time
# PID Velocity form
e[i] = sp[i] - pv[i]
P[i] = Kc * (e[i] - e[i-1])
I[i] = Kc*delta_t/tauI * (e[i])
D[i] = Kc*tauD/delta_t * (pv[i] - 2*(pv[i-1]) + pv[i-2])
op[i] = op[i-1] + P[i] + I[i] + D[i]
if op[i] < oplo or op[i] > ophi:
# clip output
op[i] = max(oplo,min(ophi,op[i]))
You can also find an example of a PID controller using a GEKKO package in the following link.
https://apmonitor.com/wiki/index.php/Main/GekkoPythonOptimization
Yes it is possible. Have you considered using someone else's code? Or do you want to write it yourself? If you have no problem using allready written code, check out Github. It has a lot of PID projects. For example PID-controller. It has a usage example and you only have to pass in your p, i and d parameters (which you allready got from Matlab).
Good luck!
Basically, you should send the values somewhere. Reading through the comments, you want to make a plot of the output variable in time, so I guess your best bet (and easier way) is to use gnuplot.
Basically, output the data in a text file, then use gnuplot to display it.
This is driving me up the wall..
I've got a very simple SDL2 program.
It has a array of 3 SDL_Texture pointers.
These textures are filled as follows:
SDL_Texture *myarray[15];
SDL_Surface *surface;
for(int i=0;i<3;i++)
{
char filename[] = "X.bmp";
filename[0] = i + '0';
surface = SDL_LoadBMP(filename);
myarray[i] = SDL_CreateTextureFromSurface(myrenderer,surface);
SDL_FreeSurface(surface);
}
This works, no errors.
In the main loop (which is just a standard event loop waiting for SDL_QUIT, keystrokes and a user-event which a SDL_Timer puts in the event queue every second) I just do (for the timer triggered event):
idx = (idx+1) % 3; // idx is global var initially 0.
SDL_RenderClear(myrenderer);
SDL_RenderCopy(myrenderer, myarray[idx], NULL, NULL);
SDL_RendererPresent(myrenderer);
This works fine for 0.bmp and 1.bmp, but the 3rd image (2.bmp) simply shows as a black field.
This is structural.
If I alternate the first 2 images they are both fine.
If I alternate the 2nd and 3rd image the 3rd image doesn't show.
If I use more than 3 images then 3 and upwards show as black.
Loading order doesn't matter. It starts going wrong with the 3rd image loaded from disk.
All images are properly formatted BMP's.
I even saved 2.bmp back to disk under a different name by using SDL_SaveBMP() after it was loaded to make sure it got loaded in memory OK. The new file is bit for bit identical to the original.
This program, without modifications and the same bmp files, works fine on OSX (XCode5) and Windows (VC++ 2012 Express).
The problem only shows on the Raspberry PI.
I have placed explicit error checks on every call that can leave a result/error-code (not shown in the samples above for brevity) but all of them show "no error".
I have used the latest stable source set of www.libsdl.org and compiled as instructed (configure, make, make install, etc.).
Anybody got any idea what could be going on ?
P.S.
Keyboard input doesn't seem to work either on my PI, but I haven't delved into that yet.
Answering myself as I finally figured it out myself...
I finally went back to the README-raspberrypi.txt that came with the SDL2 sources.
I didn't read it carefully enough the first time around...
Problem 1: I'am running on a FULL-HD display. The PI's default GPU memory is 64MB which is not enough for large displays and double-buffering. As suggested in the README I increased this to 128MB and this solved the black image problem.
Problem 2: Text input wasn't working because my user-account was not in the input group. I had added the default "pi" account to the input group initially, but when I later started using another account I forgot to add that user to the group.
In short: Caught by my own (too) quick skimming of the documentation.
I’m working on a homework project compare performance of Fast Fourier Transform on CPU vs GPU . I’m done with the CPU part , but with GPU , I have a problem.
The trouble is the kernel runtime is zero , the input is the same as the output image . I use VS2010 on win7 with AMD APP SDK . Here is the host code , the kernel , an addition header to handle the image , they can be found in The OpenCL Programming Book (Ryoji Tsuchiyama…)
My guess the error is in the phase where we pass values from the image pixels to the cl_float2 *xm (line 169-174 in the host code). I can’t access the vector component to check it either , the compiler ain’t accept .sX or .xy , throws an error about it . Other parts –kernel,header…- looks fine with me .
for (i=0; i < n; i++) {
for (j=0; j < n; j++) {
((float*)xm)[(2*n*j)+2*i+0] = (float)ipgm.buf[n*j+i]; //real
((float*)xm)[(2*n*j)+2*i+1] = (float)0; //imag
}
}
So hope you guys help me out . Any ideas will be appreciated .
OpenCL provides a lot of different error codes.
You already retrieve them by doing ret = clInstruction(); on each call, but you are not analysing it.
Please check on each call if this value is equal to CL_SUCCESS.
It may always happen, that the memory is not sufficient, the hardware is already in use or there is a simple error in your source code. The return value will tell you.
Also: Please check your cl_context, cl_program, etc. for NULL values.
I've read about the solutuon written here on a post a year ago
wx.TextCtrl.LoadFile()
Now I have a windows application that will generate color frequency statistics that are saved in 3D arrays. Here is a part of my code as you will see on the code below the printing of the statistics is dependent on a slider which specifies the threshold.
void Project1Frm::WxButton2Click(wxCommandEvent& event)
{
char stat[32] ="";
int ***report = pGLCanvas->GetPixel();
float max = pGLCanvas->GetMaxval();
float dist = WxSlider5->GetValue();
WxRichTextCtrl1->Clear();
WxRichTextCtrl1->SetMaxLength(100);
if(dist>0)
{
WxRichTextCtrl1->AppendText(wxT("Statistics\nR\tG\tB\t\n"));
for(int m=0; m<256; m++){
for(int n=0; n<256; n++){
for(int o=0; o<256; o++){
if((report[m][n][o]/max)>=(dist/100.0))
{
sprintf(stat,"%d\t%d\t%d\t%3.6f%%\n",m,n,o,report[m][n][o]/max*100.0);
WxRichTextCtrl1->AppendText(wxT(stat));
}
}
}
}
}
else if(dist==0) WxRichTextCtrl1->LoadFile("histodata.txt");
}
The solution I've tried so far is that when I am to print all the statistics I'll get it from a text file rather than going through the 3D array... I would like to ask if the Python implementation of the segmenting can be ported to C++ or are there better ways to deal with this problem. Thank you.
EDIT:
Another reason why I used a text file instead is that I observed that whenever I do sprintf only [with the line WxRichTextCtrl1->AppendText(wxT(stat)); was commented out] the computer starts to slow down.
-Ric
Disclaimer: My answer is more of an alternative than a solution.
I don't believe that there's any situation in which a user of this application is going to find it useful to have a scrolled text window containing ~16 million lines of numbers. It would be impossible to scroll to one specific location in the list that the user might need to see easily. This is all assuming that every single number you output here has some significance to the user of course (you are showing them on the screen for a reason). Providing the user with controls to look up specific, fixed (reasonable) ranges of those numbers would be a better solution, not only in regards to a better user experience, but also in helping to resolve your issue here.
On the other hand, if you still insist on one single window containing all 64 million numbers, you seem to have a very rigid data structure here, which means you can (and should) take advantage of using a virtual grid control (wxGrid), which is intended to work smoothly even with incredibly large data sets like this. The user will likely find this control easier to read and find the section of data they are looking for.
I am using TWAIN in C++ and I am trying to set the DPI manually so that a user is not displayed with the scan dialog but instead the page just scans with set defaults and is stored for them. I need to set the DPI manually but I can not seem to get it to work. I have tried setting the capability using the ICAP_XRESOLUTION and the ICAP_YRESOLUTION. When I look at the image's info though it always shows the same resolution no matter what I set it to using the ICAPs. Is there another way to set the resolution of a scanned in image or is there just an additional step that needs to be done that I can not find in the documentation anywhere?
Thanks
I use ICAP_XRESOLUTION and the ICAP_YRESOLUTION to set the scan resolution for a scanner, and it works at least for a number of HP scanners.
Code snipset:
float x_res = 1200;
cap.Cap = ICAP_XRESOLUTION;
cap.ConType = TWON_ONEVALUE;
cap.hContainer = GlobalAlloc(GHND, sizeof(TW_ONEVALUE));
if(cap.hContainer)
{
val_p = (pTW_ONEVALUE)GlobalLock(cap.hContainer);
val_p->ItemType = TWTY_FIX32;
TW_FIX32 fix32_val = FloatToFIX32(x_res);
val_p->Item = *((pTW_INT32) &fix32_val);
GlobalUnlock(cap.hContainer);
ret_code = SetCapability(cap);
GlobalFree(cap.hContainer);
}
TW_FIX32 FloatToFIX32(float i_float)
{
TW_FIX32 Fix32_value;
TW_INT32 value = (TW_INT32) (i_float * 65536.0 + 0.5);
Fix32_value.Whole = LOWORD(value >> 16);
Fix32_value.Frac = LOWORD(value & 0x0000ffffL);
return Fix32_value;
}
The value should be of type TW_FIX32 which is a floating point format defined by twain (strange but true).
I hope it works for you!
It should work the way.
But unfortunately we're not living in a perfect world. TWAIN drivers are among the most buggy drivers out there. Controlling the scanning process with TWAIN has always been a big headache because most drivers have never been tested without the scan dialog.
As far as I know there is also no test-suite for twain-drivers, so each of them will behave slightly different.
I wrote an OCR application back in the 90th and had to deal with these issues as well. What I ended up was having a list of supported scanners and a scanner module with lots of hacks and work-arounds for each different driver.
Take the ICAP_XRESOLUTION for example: The TWAIN documentation sais you have to send the resolution as a 32 bit float. Have you tried to set it using an integer instead? Or send it as float but put the bit-representation of an integer into the float, or vice versa. All this could work for the driver you're working with. Or it could not work at all.
I doubt the situation has changed much since then. So good luck getting it working on at least half of the machines that are out there.