How to detect motion and movement in Wowza? Is there any module that is present in Wowza? If it is present, then please help to find out that module and give me the url or any documentation for that.
If it is not present, then please help to find out that how to create that module in wowza media system by providing any link, url, documentation for that.
The Wowza Transcoder API offers an onGrabFrame() callback:
public void onGrabFrame(TranscoderNativeVideoFrame videoFrame) {
BufferedImage image = TranscoderStreamUtils.nativeImageToBufferedImage(videoFrame);
if (image != null)
{
// do something with frame data
}
}
Once you grab the frame data you can feed it to an algorithm that detects scene changes (eg: using the Sum of absolute differences).
There's also an open-source computer vision project called OpenCV which supports Java and has many features.
Related
Currently, I am trying to create a virtual camera with the Media Foundation API. However, creating a virtual camera requires a IMFMediaSource, which is used to provide video source to the camera.
It would be appreciated if anyone can help me to answer the following questions
How to create a media source from a given video path? A code example or a step by step tutorial could really help me to understand how can I use the API.
How does the video "goes into" the IMFMediaSource? Is it loaded into the memory?
How is the video processed before getting outputed as a stream?
I am developing an C++ application which should use an USB camera to capture high resolution photos. It should have same behavior as the Camera application in Windows 10. I am trying to use DirectShow for doing it. Now I am only able to take high resolution photo which is delayed or take a photo in time but low resolution. Also I am very confused from MS documentation, lot of things are deprecated and nowhere mentioned what replaces them. I'll describe my hopeless steps awaiting there will be somebody who could be able to show me a way.
Let's start from beginning...
Knowing nothing about video capturing in Window I started by searching suitable library. After some googling I found there are four main libraries for capturing video in Windows.
Video for Windows
DirectShow
Windows Media Foundation
OpenCV
Let's observe:
Video for Windows
This library is unfortunately marked as deprecated but it seems it still works. I have written "unfortunately", because I think this is the only which is easy to use. There are only a few lines of code needed for seeing video from camera. The only think I miss here is a "TakePhoto" function. You can use VFW for capture a video or single frames to an avi file. Or am I missing something?
DirectShow
This is much more complicated library. You need hundreds of lines of code to see a video preview. But you can obtain this code on MS Docs. Ok, now I have a video preview and I need only to take a photo. One would expect this should be just one function call. But where is the function? I did not find it.
You can simply use GetCurrentImage from IVMRWindowlessControl but this takes only one frame from preview with low resolution. If you set a higher resolution for preview the video is not fluent.
Best approach I could achieve is from an article called "Capturing an Image From a Still Image Pin" available here https://learn.microsoft.com/en-us/windows/desktop/directshow/capturing-an-image-from-a-still-image-pin. When I had found this site I thought I won and my task was almost finished. But it wasn't.
The first advice which the article gives you is not to use it: "The recommended way to get still images from the device is to use the Windows Image Acquisition (WIA) APIs. For more information, see "Windows Image Acquisition" in the Platform SDK documentation. However, you can also use DirectShow to capture an image." I tried to explore the WIA. But this stopped to work on Vista. I continued to study the article.
Everything seems to be clear but you need to implement your class which inherits ISampleGrabberCB marked as deprecated here https://learn.microsoft.com/en-us/windows/desktop/directshow/isamplegrabbercb. Why???? Where to find some alternative?
I found an acceptable solution here https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/2ab5c212-5824-419d-b5d9-7f5db82f57cd/qedith-missing-in-current-windows-sdk-v70?forum=windowsdirectshowdevelopment. You need to add header file from elder SDK. (BTW This is an advice almost ten years old.) After I compiled the application with this header I was able to read high resolution picture but I need to wait a few seconds which is unacceptable. I know the problem is not in camera, because in the it works in the Camera application. Furthermore the image is obtained in function SampleCB instead of BufferCB and is in some strange format. I can save it as jpg but it is not compressed enough.
Windows Media Foundation
I think MS doesn't like programmers and that's why it released WMF. I understand nothing. I found this tutorial https://www.dreamincode.net/forums/topic/347938-a-new-webcam-api-tutorial-in-c-for-windows/. It works but it only stores one frame from preview and this is not what I want.
Next I explored some WMF interfaces on MS Docs. IMFCapturePhotoSink interface should do the stuff. But how implement it. The documentation is useless.
OpenCV
During my research I found also this library. But again I'm not able to take a high resolution photo. It only stores one frame from preview.
Could someone tell me what should I focus on? I believe it cannot be so difficult. There are tens and hundreds of applications for webcams. How could other programmers implement them? What's wrong with me? I'd like to find an easy way to implement an easy task. Thank a lot for any help.
You question is not related to the topic - the question must be related to the code - but I faced with the similar problem many years ago and I had found solution:
DirectShow is declared as deprecated for Windows 10 and it has problem with supporting of the USB web cam. In Windows 10 there is USB Video Class which is supported only by Media Foundation.
So, I have wrote a simple C++ wrapper around Media Foundation code which simplify getting of the raw images Capturing Video from Web-camera on Windows 7 and 8 by using Media Foundation
Also, there is project CaptureManager SDK - it is DLL COM component with the simple interfaces, huge functionality and with many demo programs on C++, Python, C#, Java.
Thanks to Evgeny.
Recapitulation:
Download the CaptureEngine video capture sample
Edit CaptureManager::TakePhoto method. Add the code to find highest resolution media type just before CreatePhotoMediaType(pMediaType, &pMediaType2); line
Extra code for setup the photo stream to highest resolution:
DWORD dwMediaTypeIndex = 0;
UINT32 maxSize = 0;
DWORD maxSizeIndex = 0;
while (1) {
IMFMediaType* pMediaType = NULL;
hr = pSource->GetAvailableDeviceMediaType((DWORD)MF_CAPTURE_ENGINE_PREFERRED_SOURCE_STREAM_FOR_PHOTO, dwMediaTypeIndex, &pMediaType);
if (hr == MF_E_NO_MORE_TYPES)
break;
UINT32 w, h;
MFGetAttributeSize(pMediaType, MF_MT_FRAME_SIZE, &w, &h);
UINT32 size = w * h;
if (size > maxSize) {
maxSize = size;
maxSizeIndex = dwMediaTypeIndex;
}
SafeRelease(&pMediaType);
dwMediaTypeIndex++;
}
SafeRelease(&pMediaType);
pSource->GetAvailableDeviceMediaType((DWORD)MF_CAPTURE_ENGINE_PREFERRED_SOURCE_STREAM_FOR_PHOTO, maxSizeIndex, &pMediaType);
I am creating sample application using Windows Media Foundation.
I have used Source Reader IMFSourceReader to Read the media file and then After I am processing the samples IMFSamples using Custom MFT IMFTransform.
In the MFT I have processed IMFSamples, How can I play/display them in a windows. I don't want to use EVR for display.
Also I have read the question:
How to play IMFMediaSample in media foundation?
As per the suggestion I need to use MFPlay for playing the samples, but exactly how this can be done.
In the interface IMFPMediaPlayer I am not able to find any method where I can push the media samples.
https://msdn.microsoft.com/en-us/library/windows/desktop/dd374329(v=vs.85).aspx
IMFSample is a wrapper over raw data. If you happen to waive standard API offering for playback/presentation (such as EVR for video), you will have to extract the data from the media sample object and consume it otherwise, such as using another API at your discretion.
This does not have to be visualization exactly, you are not limited in consumption ideas: writing to file, sending via network etc. For visualization you have other Windows APIs at your choice: DirectX, DirectShow, legacy DirectDraw, GDI, GDI+, Direct2D etc.
IMFSample is not immediately accepted by other APIs right away because it is not what it is designed for. In Media Foundation API EVR is designed for presentation, and EVR is what you are supposed to use.
The video sample object is a specialized implementation of the IMFSample interface for use with the Enhanced Video Renderer (EVR)...
Background:
I have a google glass, and I am thinking on an app that can grab any/all images a user takes using the native camera, and passing those images to an online service (e.g. Twitter or Google+). Kind of like a life-blogging style application.
In my first prototype, I implemented a FileObserver Service that watches for new files in the directory that glass stores its camera preview thumbnails (sdcard/google_cached_files/). The preview files always started with t_, so once I saw a new file there, I uploaded it to my webservice. This was working very well, but in Glass XE11 this cache file was moved out of my reach (/data/private-cache).
So now, I am watching the folder sdcard/DCIM/Camera/ for new .jpg files. This works ok, but the camera is storing the full size image there, so I have to wait 5-8 sec before the image is available for upload.
The Question:
Should it be possible to have background service running on glass that can intercept the camera event, and grab the thumbnail or the full image as a byte array from the Bundle so that I don't have to wait for it to write to disk before accessing it?
I have been reading up more on android development, and I suspect the answer involves implementing a BroadcastReciever in my service, but I wanted to check with the experts before going down the wrong path.
Many thanks in advance
Richie
Yes. Implement a PreviewCallback. Same way it worked for phones, example here: http://www.dynamsoft.com/blog/webcam/how-to-implement-a-simple-barcode-scan-application-on-android/
I tested it on Google Glass and it works. In this post ( http://datawillconfess.blogspot.com.es/2013/11/google-glass-gdk.html ) I list the parameters (below the video) which the camera returns after doing:
Camera m_camera = Camera.open(0);
m_params = m_camera.getParameters();
m_params.setPreviewFormat(ImageFormat.NV21);
m_camera.setParameters(m_params);
m_params = m_camera.getParameters();
m_params.setPreviewSize(320,240);
m_params.set("focus-mode",(String)"infinity");
m_params.set("autofocus", "false");
m_params.set("whitebalance",(String)"daylight");
m_params.set("auto-whitebalance-lock",(String)"true");
m_camera.setParameters(m_params);
String s = m_params.flatten();
Log.i("CAMERA PARAMETERS", "="+s);
What is a good platform for a web based project that does image processing using OpenCV library? I found Wt ( http://www.webtoolkit.eu/wt ).
Can I use OpenCV with Wt ? Is there any better alternatives to Wt?
Requirements:
A login page GUI to
upload documents,
select areas on image,
handwriting word/line detection using OpenCV
I've used Wt in the past, it is very useful, albeit bulky. It's bloat has to do with having to support a wide variety of web browsers, so in some cases it is a feature.
If you're more of a close-to-metal programmer, I'd recommend PION, and implementing your GUI using some of your web authoring skills:
http://www.pion.org/projects/pion-network-library
You can use OpenCV with pretty much any network library out there. A good review of your choices is available here on StackOverflow:
https://stackoverflow.com/questions/175507/c-c-web-server-library
I think what you ask is possible with Wt. I cannot foresee problems with linking OpenCV in Wt, and the system is definitely interactive enough to provide the functionality you describe. Implement it with server-side actions first, and if required, you can still optimize parts with small bits of client-side JS.
FWIW, this is a simple code to display OpenCV image (possibly changing the image while the app is running):
Wt::WMemoryResource* cvMat2res(const cv::Mat& img){
std::vector<uchar> buf;
cv::imencode(".png",img,buf); // by default, the fastest compression
auto ret=new Wt::WMemoryResource(this);
ret->setMimeType("mime/png");
ret->setData(buf); // data is copied here
return ret;
}
/* ... */
auto img=new Wt::Image();
root()->addWidget(img);
Wt::WMemoryResource* imgRes=nullptr;
/* set image data; this can be done also in event handler and the image updates itself automatically from the new resource */
if(imgRes) delete imgRes;
imgRes=cvMat2res(cvImage);
img->setImageLink(imgRes);