I need to use DirectShow (C++) for recording a webcam and saving the data to a file.
I really don't know how DirectShow works, this is a "stage" (working experience), but at school we didn't study it.
I think the best way to implement this could be:
List the video devices connected to the computer
Select the correct camera (there will be only one)
Retrieve the video
Save it to a file
Now there are two problems:
Where can I find a good reference book or how do I start?
The saved video shouldn't be too big, does DirectShow provide a way to compress it?
I won't use OpenCV because sometime it doesn't work properly (It doesn't find the camera).
Are there any high level wrapper that could help?
EDIT: the program won't have a window, it will run in background called by a dll.
Where can I find a good reference book or how do I start?
DirectShow introduction material
The saved video shouldn't be too big, does DirectShow provide a way to compress it?
Yes it provides capabilities to attach codecs, that needs to be installed in the system. These are typically third party codecs (for reasons beyond the scope of brief answer). You might want to record into Windows Media files to not depend on third party codecs. SWee more on MSDN: Choosing a Compression Filter.
Related
I have written a program using SFML Library (in C++) rendering simple 2D animation.
I would like to save the animation to a video file instead of drawing it on the screen.
Does SFML provide such functionality? Is there any other, portable way to do this? (portable between different OSes)
SFML does not have such a feature, especially since video processing is a whole world of its own. You can take a look at FFmpeg and GStreamer. Both libraries are cross-platform and should be able to record, playback and stream videos. If you want a specific codec, you could directly look at the codec's website and/or search for good encoder.
Overall it's not an easy task and depending on what you're trying to do, you could also think about grabbing the rendering directly with an third-party application, e.g. Open Broadcaster Software or (again) FFmpeg.
I am trying to replicate the image quality that is achieved when using the Logitech webcam driver to capture a still image.
The Logitech forum has several threads about the subject unfortunately they all point to a website which is down. such as here.
I am currently able to use DirectShow and a frame grabber to capture images, but they are nowhere near the quality of the snapshot button. Could anyone point me to the direction of a working c++/c example of a snapshot button?
After some research I found this about the Still Image pin, is this the correct method for implementing a snapshot like button?
The webcam I am using the c910 and is capable of taking 10 mega-pixel still images.
Thanks for any help.
My best guess, which I'll use to gather some upvotes (or downvotes), and which will be valid until someone disassembles the application or the driver, is:
Something alike http://www1.idc.ac.il/toky/videoproc-07/projects/superres/srproject.html was used at the application level to enhance the resolution of the images collected as a video.
Rationale: having a friend pulling his hair over simpler things inside the driver, I can only imagine how difficult it should be to code such an algorithm INSIDE the driver with extremely limited set of libraries.
I won't mind taking downvotes here, since I'm too interested in this subject, but please have some information available on the subject.
I did not have a chance to deal with this directly, however I suspect that high resolution images captured from the camera are a result of taking a sequence of images followed by "superresolution" post-processing. This functionality might be unavailable via DirectShow API, since it mostly covers video streaming. However, the camera driver might also make it available via Windows Image Acquisition API, where you might have better luck taking oversampled snapshots of the quality you are looking for.
I am looking for a fast way to load in a video file and to create images from them at certain intervals ( every second, every minute, every hour, etc.).
I tried using DirectShow, but it just ran too slow for me to start the video file and move to a certain location to get data and to save it out to an image. Even if I disabled the reference clock. Tried OpenCV, but it has trouble opening the AVI file unless I know the exact codec information. So if I know a way to get the codec information out from OpenCV I may give it another shot. I tried to use FFMPEG, but I don't have as much control over it as well as I would wish.
Any advice would be greatly appreciated. This is being developed on a Windows box since it has to be hosted on a Windows box.
MPEG-4 format is not an intra-coded format, so you can't just jump to a random frame and decode it on its own, as most frames only encode the differences from one or more other frames. I suspect your decoding is slow because when you land on a frame for which several other dependent frames to be decoded first.
One way to improve performance would be to determine which frames are keyframes (or sometimes also called 'sync' points) and limit your decoding to those frames, since these can be decoded on their own.
I'm not very familiar with DirectShow capabilities, but I would expect it has some API to expose sync points.
Also, I should mention that the QuickTime SDK on Windows is possibly another good option that you have for decoding frames from movies. You should first test that your AVI movies are played correctly in the QuickTime Player. And the QT SDK does expose sync points, see the section Finding Interesting Times in the QT SDK documentation.
ffmpeg's libavformat might work for ya...
What should I use to perform screen capture on Windows for subsequent image processing?
I seek to do follow-up image processing in OpenCV.
Well the most straightforward thing to do is to use an off the shelf video capture tool to create an AVI file and then have image processing software operate on that, after the fact.
To get up and running:
CamStudio is free and open source and has a simple gui.
VirtualDub is also FOSS and is more powerful, but less intuitive to use. Its primarily a video editing and processing tool, but it actually has sophisiticated capture capabilities.
Both work on Windows and both can output uncompressed AVI files that OpenCV can read.
If you are completely new to OpenCV, then I recommend a O'Reilly's "Learning OpenCV". Its for the older OpenCV 1.1 but it will at least get you started.
If you crack open that book, and you find that its way above your head, then I would consider trying to do your image processing in a higher level language. MATLAB with the Image Processing Toolbox is well suited for rapid prototyping of image processing and its a much more forgiving development environment. Its an interpretative language, so you can see-as-you-code.
Based on the question as stated, this is as much info as I can provide. Perhaps consider providing more details about your specific application requirements?
I have made two different solutions for Video-to-Image Capturing and was wondering if I could intertwine the best of both worlds. I am currently using DirectShow to load in an AVI file and capture images. However, DirectShow's lack of image processing capabilities and the need to make additional filters have stopped me dead in my tracks.
I then turned to OpenCV.
It has all the image processing functions I need, but it has trouble loading in the videos that the DirectShow solution was able to retrieve. Are there any tutorials online about this process or anything close to it? Thanks for any advice.
Yes, here is a link to an article: http://opencv.willowgarage.com/wiki/DirectShow