I'm using openCV 1.1pre1 under Windows. I have a network camera and I need to grab frames from openCV. That camera can stream a standard mpeg4 stream over RTSP or mjpeg over http. I've seen many threads talking about using ffmpeg with openCV but I cannot make it work.
How I can grab frames from an IP camera with openCV?
Thanks
Andrea
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Use ffmpeglib to connect to the stream.
These functions may be useful. But take a look in the docs
av_open_input_stream(...);
av_find_stream_info(...);
avcodec_find_decoder(...);
avcodec_open(...);
avcodec_alloc_frame(...);
You would need a little algo to get a complete frame, which is available here
http://www.dranger.com/ffmpeg/tutorial01.html
Once you get a frame you could copy the video data (for each plane if needed) into a IplImage which is an OpenCV image object.
You can create an IplImage using something like...
IplImage *p_gray_image = cvCreateImage(size, IPL_DEPTH_8U, 1);
Once you have an IplImage, you could perform all sorts of image operations available in the OpenCV lib
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I've seen in many threads that ffmpeg is already included and used inside openCV, is this right? Maybe I need to recompile openCV with ffgmpeg support? In this case how I can do this under windows? Thanks – Grifo Apr 3 '09 at 12:36
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I'm not aware of this. However, ffmpeg is an application where as ffmpeglib is a library. If you are new to these please look at the dranger.com tutorials. – Indeera Apr 3 '09 at 13:19
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OpenCV can be compiled with FFMPEG support. From ./configure --help:
--with-ffmpeg use ffmpeg libraries (see LICENSE) [automatic]
You can then use *cvCreateFileCapture_FFMPEG* to create a CvCapture with e.g. the URL of the camera's MJPG stream.
I use this to grab frames from an AXIS camera:
CvCapture *capture =
cvCreateFileCapture_FFMPEG("http://axis-cam/mjpg/video.mjpg?resolution=640x480&req_fps=10&.mjpg");
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Is it possible to configure openCV with ffmpeg support under Windows? – Grifo Jun 25 '09 at 9:37
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I just do it like this:
CvCapture *capture = cvCreateFileCapture("rtsp://camera-address");
Also make sure this dll is available at runtime else cvCreateFileCapture will return NULL
opencv_ffmpeg200d.dll
The camera needs to allow unauthenticated access too, usually set via its web interface. MJPEG format worked via rtsp but MPEG4 didn't.
hth
Si
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Are you using OpenCV 2.0? – Grifo Mar 2 at 8:41
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The library version says that he is using openCV 2.0 - that's the
200 part in opencv_ffmpeg200d.dll – jamuraa Mar 17 at 20:41 |