We have a c# application that performs processing on video streams. This is a low-level application that receives each frame in Bitmap format, so basically we need 25 images each second. This application is already working for some of our media sources, but we now need to add a webcam as an input device.
So we basically need to capture bitmap images from a webcam continuously so that we can pass all these frames as a "stream" to our application.
What is the best and simplest way to access the webcam and read the actual frames directly from the webcam as individual images? I am still in the starting blocks.
There are a multitude of libraries out there that allows one to access the webcam, preview the content of the webcam on a windows panel and then use screen capturing to capture this image again. This, unfortunately, will not give us the necessary performance when capturing 25 frames per second. IVMRWindowlessControl9::GetCurrentImage has been mentioned as another alternative, but this again seems to be aimed at an infrequent snapshot rather than a constant stream of images. Directshow.Net is mentioned by many as a good candidate, but it is unclear how to simply grab the images from the webcam. Also, many sources state a concern about Microsoft no longer supporting Directshow. Also, implementations I've seen of this requires ImageGrabber which is apparently also no longer supported. The newer alternative from MS seems to be Media Foundation, but my research hasn't turned up any working examples of how this can be implemented (and I'm not sure if this will run on older versions of windows such as XP). DirectX.Capture is an awesome library (see a nice implementation) but seems to lack the filters and methods to get the video images directly. I have also started looking at Filters and Filter Graphs but this seems awfully complex and does feel a bit like "reinventing the wheel".
Overall, all the solutions briefly mentioned above seem to rather old. Can someone please point me in the direction of a step-by-step guide for getting a webcam working in C# and grabbing several images per second from it? (We will also have to do audio at some point, so a solution that does not exclude video would be most helpful).
I use AForge.Video (find it here: code.google.com/p/aforge/) because it's a very fast c# implementation. i am very pleased with the performance and it effortlessly captures from two HD webcams at 30fps on an 8 year old PC. the data is supplied as a native IntPtr so it's ideal for further processing using native code or opencv.
opencv wrappers emgu and opencvsharp both implement a rudimentary video capture functionality which might be sufficient for your purposes. clearly if you are going perform image processing / computer vision you might want to use those anyway.
As dr.mo suggests, Aforge was the answer.
I used the tutorial from here: http://en.code-bude.net/2013/01/02/how-to-easily-record-from-a-webcam-in-c/
In the tutorial, they have an event handler fire each time a frame is received from the webcam. In the original tutorial, this bitmap is used to write the image to a PictureBox. I have simply modified it to save the bitmap image to a file rather than to a picturebox. So I have replaced the following code:
pictureBoxVideo.BackgroundImage = (Bitmap)eventArgs.Frame.Clone();
with the following code:
Bitmap myImage = (Bitmap)eventArgs.Frame.Clone();
string strGrabFileName = String.Format("C:\\My_folder\\Snapshot_{0:yyyyMMdd_hhmmss.fff}.bmp", DateTime.Now);
myImage.Save(strGrabFileName, System.Drawing.Imaging.ImageFormat.Bmp);
and it works like a charm!
Related
I am trying to open a video in my application to process on the frames and then save the results into another video. I used OpenCV (Emgu) for my image processing with no issues. But I cannot use it properly for processing videos as it pops "Access Violation" exception from time to time. Also I want to keep the audio track of the video for the output. So I just want to iterate through the frames in simple C# code and use my Emgu function on each frame.
These are desirable for my app:
Keeping the audio
Video codec/compression support
Fast performance
Opencv is a library mainly for Computer Vision stuff and so there's no built-in function that let you process audio data.
There's a similar question with a solution here on stackoverflow:
Adding audio to video produced from OpenCV
To take advantage of FFMPEG and it's related softwares take a look here:
http://opencv.willowgarage.com/wiki/FFMPEG
The Access Violation error you are facing using Emgu may be related to some emgu or opencv bugs, the 2.2 version has some known with video saving.
I have a Microsoft LifeCam HD-5000 webcams. According to AMCap, the camera outputs a MJPEG stream at 30fps at 720p. I want to capture each JPEG frame in a small application without doing any preview or decompression/transcoding to minimize CPU utilization to the minimum possible.
I'm a C# developer, but I'm new to DirectShow. Is there a simple way to capture the MJPEG stream frame by frame as its output from the camera in C#/.NET without decompressing it?
First of all, you might not need to use DirectShow to access your camera. Check out the OpenCV project, which has .net bindings available at opencvdotnet.
If you'd like to go the DirectShow route, then you'll need the .NET bindings, available at the directshownet project. I believe your best bet will be to create a filter graph that contains your webcam as a source filter, and a sample grabber as your destination filter. Documentation for the sample grabber is on MSDN. This will give you access to the raw data. You can also request a particular data format and use the DirectShow intelligent connect to fill in the filter graph with the right conversion filters.
That being said, I definitely recommend OpenCV over DirectShow. DirectShow is very general purpose, and probably does more than you need it to do. OpenCV can be used to quickly access your camera. Perhaps check out this stackoverflow question Webcam Usage in C# for some more information and answers.
With DirectShowNet, I could never access to a single frame and show it as Bitmap anywhere. In every project I just see converters, direct show to screen or streaming. How to capture the stream as single bitmap frames?
in the Directshow.net Download package, they have sample code and inside Capture there is a project DxSnap which connects to a webcam through directshow.net and snaps a picture from the stream. You can view it and use that as a starting place.
I am making an object tracking application. I have used Emgucv 2.1.0.0
to load a video file
to a picturebox. I have also taken the video stream from a web camera.
Now, I want
to draw an unfilled square on the video stream using a mouse and then track the object enclosed
by the unfilled square as the video continues to stream.
This is what people have suggested so far:-
(1) .NET Video overlay drawing(DirectX) - but this is for C++ users, the suggester
said that there are .NET wrappers, but I had a hard time finding any.
(2) DxLogo sample
DxLogo – A sample application showing how to superimpose a logo on a data stream.
It uses a capture device for the video source, and outputs the result to a file.
Sadly, this does not use a mouse.
(3) GDI+ and mouse handling - this area I do not have a clue.
And for tracking the object in the square, I would appreciate if someone give me some research paper links to read.
Any help as to using the mouse to draw on a video is greatly appreciated.
Thank you for taking the time to read this.
Many Thanks
It sounds like you want to do image detection and / or tracking.
The EmguCV ( http://www.emgu.com/wiki/index.php/Main_Page ) library provides a good foundation for this sort of thing in .Net.
e.g. http://www.emgu.com/wiki/index.php/Tutorial#Examples
It's a pretty meaty subject with quite a few years and different branches of research associated with it so I'm not sure anyone can give the definitive guide to such things but reading up neural networks and related topics would give you a pretty good grounding in the way EmguCV and related libraries manage it.
It should be noted that systems such as EmguCV are designed to recognise predefined items within a scene (such as a licence plate number) rather than an arbitory feature within a scene.
For arbitory tracking of a given feature, a search for research papers on edge detection and the like (in combination with a library such a EmguCV) is probably a good start.
(You also may want to sneak a peek at an existing application such as http://www.pfhoe.com/ to see if it fits your needs)
I want to create a simple video renderer to play around, and do stuff like creating what would be a mobile OS just for fun. My father told me that in the very first computers, you would edit a specific memory address and the screen would update. I would like to simulate this inside a window in Windows. Is there any way I can do this with C#?
This used to be done because you could get direct access to the video buffer. This is typically not available with today's systems, as the video memory is managed by the video driver and OS. Further, there really isn't a 1:1 mapping of video memory buffer and what is displayed anymore. With so much memory available, it became possible to have multiple buffers and switch between them. The currently displayed buffer is called the "front buffer" and other, non-displayed buffers are called "back buffers" (for more, see https://en.wikipedia.org/wiki/Multiple_buffering). We typically write to back buffers and then have the video system update the front buffer for us. This provides smooth updates, as the video driver synchronizes the update with the scan rate of the monitor.
To write to back buffers using C#, my favorite technique is to use the WPF WritableBitmap. I've also used the System.Drawing.Bitmap to update the screen by writing pixels to it via LockBits.
It's a full featured topic that's outside the scope (it won't fit, not that i won't ramble about it for hours :-) of this answer..but this should get you started with drawing in C#
http://www.geekpedia.com/tutorial50_Drawing-with-Csharp.html
Things have come a bit from the old days of direct memory manipulation..although everything is still tied to pixels.
Edit: Oh, and if you run into flickering problems and get stuck, drop me a line and i'll send you a DoubleBuffered panel to paint with.
I'm looking at trying to create a simple 'slider puzzle' game. You've seen the ones, you have an image and you shuffle the tiles.
However, I want to make one that will play back videos instead. What I'm trying to determine is whether it's possible to playback a video in C# and render the video on different controls (probably buttons, or panels). I've spotted the Microsoft.DirectX.AudioVideoPlayback classes but haven't found much documentation on them yet.
So to throw it up in the air, is this going to be possible to do without too much difficulty? Are there any useful (free) libraries that might help me along?
Have a look at DirectShowNet that wraps the DirectShow API, in the samples page there is a sample called PlayWnd the shows how to play a video file.
Depending upon how large and how long your video sources are, you could accomplish this very simply by first converting your videos to animated GIFs. A .Net PictureBox control will display and animate a GIF automatically, and you could easily use PictureBoxes for your tiles.
One big advantage of this approach is that (thanks to Mono) your application could work unaltered on Windows, Mac and the iPhone (also Linux and a couple others).