I'm working with C# and VLC library, and I wonder if there is way to get hands to VLC buffer (netwoking-cache or so).
What I could use, is to save that to my own circular buffer and save it IF needed.
Is this possible, or should I just do it with "manualy" on other stream?
There are audio and video callbacks that allow you to access the raw data using libvlc. It does slow down the perf though, understandably.
This sample https://code.videolan.org/mfkl/libvlcsharp-samples/-/blob/master/PreviewThumbnailExtractor/Program.cs shows you how to use the video callbacks to extract frames.
This should be a good starting point for achieving whatever you need to do.
Related
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!
I am looking for a effective way to compress a real time video stream. In my project, the streaming seems important because my system will send and receive both the audio and video streams at the same time. I am considering using H261 or H263. How can I achieve such compression ratio using C#?
PS I found something called H323Plus, but I do not know how to call this library because it is written in C++.
If you want to do real-time streaming over UDP with both audio and video stream you can use the DirectShow API (if you're targeting Windows).
http://msdn.microsoft.com/en-us/library/windows/desktop/dd375454(v=vs.85).aspx
You will find a .NET wrapper for DirectShow here
http://directshownet.sourceforge.net/
You will also find more samples on codeproject.com, most of them use this wrapper
http://www.codeproject.com/kb/audio-video/#DirectShow
If you plan on targeting Windows 7 and newer only, then you will want to use Windows Media Foundation API
http://msdn.microsoft.com/en-us/library/windows/desktop/ms694197(v=vs.85).aspx
I need to be able to record video from an external camera in a C# application.
Unfortunately a webcam is pretty much out of the question as the application will record outside and during the evening/night. That is why I was thinking of a camcorder since it also has manual control over exposure and focus, lower noise and better sensor.
So far I would use the AV/S-Video output from the camcorder and send the signal to a USB capture card (the computer is a laptop so no PCI-E cards).
How would I be able to access the video stream from the C# application, now that it comes from the capture card ?
Does my proposed system seem feasible (achievable, good video quality, good fps)? Does anybody have another working solution?
Thanks
This Code Project Article could be of a good starting point.
The Author mentions :
The main goal of the application was to make it flexible and
extensible. The application itself can communicate with any video
source – it may be an IP video camera or a server, it may be a local
camera attached to USB, it may be an MMS stream from a remote server,
or it may be any other video source. And more of it, the application
can work with all these video sources simultaneously, displaying them
all on a single screen.
The solution I used in the end was Microsoft Expression Encoder.
I have looked at some of the VLC wrappers but haven't tried them yet. Does anyone have any suggestions?
If you can do this in the background and it doesn't need to be realtime, I recommend shelling this out to FFMPEG.
FFMPEG can handle tasks like this very easily, and it isn't worth the headache to do this natively in .NET, unless you have to. (If you were, you'd want to look into DirectX.)
There appears to be a C# wrapper for .NET, but I have no experience with it. I should also point out that FFMPEG supports STDIN/OUT.
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.