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2017-04-05 13:25:11 -0500 asked a question ONVIF support

Hey there,

I can connect my OpenCV program with RTSP streams, except with the ones that ends with onvif1. E.g. rtsp://

Does anyone knows why this might not work as expected?


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2017-02-25 15:47:41 -0500 asked a question SIGSEGV while write video with x264 encoder


I'm using the OpenCV VideoWriter to create some video's. The good news that it works, but unfortunately isn't very stable. The system crashes randomly with a segmentation fault.

I've debugged with GDB and located the issue with libx264. I was wondering if I could do something about it? Is it caused by writing a wrongly formatted image? I have this issue with IP camera's and USB camera's.

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7a7ff450 (LWP 26862)]
0x00b27748 in x264_encoder_encode ()
(gdb) bt
Python Exception <type 'exceptions.ImportError'> No module named gdb.frames: 
#0  0x00b27748 in x264_encoder_encode ()
#1  0x007868fc in ?? ()
2017-01-31 00:57:30 -0500 answered a question Need OpenCV expert near BARCELONA for job

I live in Belgium, and can work remote. More information on and

2017-01-30 12:01:29 -0500 commented question Linking error carotene Opencv 3.2 on ARM

Well i'm building it for an ARM device, though the OpenCV library is compiled correctly. I think I'm just missing to include a library for linking?

2017-01-30 10:36:02 -0500 asked a question Linking error carotene Opencv 3.2 on ARM


I have succesfully build OpenCV 3.2.0 on an ARM device. However when linking my binary I got exceptions from carotene.

split.cpp:(.text._ZN2cv3hal7split8uEPKhPPhii+0x18): undefined reference to `carotene_o4t::isSupportedConfiguration()'
split.cpp:(.text._ZN2cv3hal7split8uEPKhPPhii+0x1ec): undefined reference to `carotene_o4t::split2(carotene_o4t::Size2D const&, unsigned char const*, int, unsigned char*, int, unsigned char*, int)'
split.cpp:(.text._ZN2cv3hal7split8uEPKhPPhii+0x2b4): undefined reference to `carotene_o4t::split4(carotene_o4t::Size2D const&, unsigned char const*, int, unsigned char*, int, unsigned char*, int, unsigned char*, int, unsigned char*, int)'

Am I missing a library?


2016-12-23 10:43:51 -0500 commented question Videowriter recording MP4 + X264 (OpenCV 3.1)

Looks like someone used the same trick:

2016-12-23 10:39:05 -0500 commented question Videowriter recording MP4 + X264 (OpenCV 3.1)

if I replace the fourcc by 0x00000021 the error goes away, but still not clear what this codec is?

2016-12-23 09:28:14 -0500 commented question Videowriter recording MP4 + X264 (OpenCV 3.1)

Should I just swap the FOURCC with H263 or is it something else? FYI I compiled FFMPEG with h264 support.

2016-12-23 09:12:13 -0500 commented question Videowriter recording MP4 + X264 (OpenCV 3.1)

I used this CV_FOURCC('X','2','6','4'). I've tried it with other containers (mkv and avi), and I can confirm that it works. However the reason I want to use MP4, is because if I use the containers (mkv or avi), it doesn't get displayed in the HTML5 video element (in Safari and Firefox); though Chrome can handle it.

Therefore I prefer to have the MP4 container, as this works in all browsers (Firefox, Safari, and Chrome).

2016-12-23 08:02:54 -0500 asked a question Videowriter recording MP4 + X264 (OpenCV 3.1)

I'm trying to record a video with the X264 codec and MP4 format. The resulting video recording works, and can be played with a videoplayer, however I receive following warning.

OpenCV: FFMPEG: tag 0x34363258/'X264' is not supported with codec id 28 and format 'mp4 / MP4 (MPEG-4 Part 14)' OpenCV: FFMPEG: fallback to use tag 0x00000021/'!???'

I've been looking in the OpenCV code and it looks that a fallback mechanism is used (and another tag is used instead). Can someone tell me why this is happening, and how I can remove the warning.

Thanks! Cédric

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2016-12-08 04:08:25 -0500 asked a question looks for OpenCV developers

Hey, we have this awesome video surveillance project built on OpenCV. If you want to contribute to this project and the OpenCV community this is the perfect place to see OpenCV in action and used by regular users. More information on and

If you see any features which aren't implemented or see improvements please write it down here.

Thanks! Cédric

2016-12-07 13:41:15 -0500 commented question VideoWriter with variable FPS

thanks, well that will fill the gaps and may work. Curious if there any other approaches.

2016-12-07 13:17:28 -0500 received badge  Editor (source)
2016-12-07 13:16:50 -0500 asked a question VideoWriter with variable FPS


I've been struggling with this one for a very long time. I have a couple of IP camera's connected through a WIFI connection, what I would like to achieve is to record the stream of each of those cameras by using the VideoWriter class.

An issue I have is that the FPS is depending on the WIFI connection. If the connection goes slower, the FPS defined in the constructor of the VideoWriter, does not match with the actual FPS retrieved.

Is there anyone here who've found a workaround for this type of situations? The big issue is that the video is playing at different speeds.

Thank you all for your help and advice.

PS: please don't recommend sleep or blocking functions, this will not help.


2016-02-15 08:59:47 -0500 commented answer Display IplImage in webbrowsers

Got it working, i've splitted your write method in two functions calls, and implemented an vector which contains all the client id's.

1) Use select to check if some new clients have subscribed, and if so create an descriptor for them.

2) In the second method send an image to all the subscribed sockets.

A crucial configration was the following:

setsockopt(client, SOL_SOCKET, SO_NOSIGPIPE, (void *)&set, sizeof(int));

This causes the program to not exit when trying to write to a disconnected client. It now works in all browsers + VLC. However Chrome does a strange thing, it always disconnects the first connection and keeps the second connection. (this is fixed by the option mentioned above).

2016-02-15 06:43:44 -0500 commented answer Display IplImage in webbrowsers

Thanks, maybe you can contribute ;)

2016-02-15 06:32:21 -0500 commented answer Display IplImage in webbrowsers

PS: I also tried it with VLC, and the code doesn't work either. It only reacts on the first HTTP request, but blocks on the select afterwards.

2016-02-15 06:28:57 -0500 commented answer Display IplImage in webbrowsers

I don't have enough knowledge of sockets.. So don't think I can help you with this. I really want to integrate your code in my project

2016-02-15 06:10:18 -0500 commented answer Display IplImage in webbrowsers

Hello berak, i'm trying your code ons OSX Yosemite. However when opening the page (e.g. with Chrome) the page keeps loading. I did some small debugging and it looks like your code is never sending the image with header to the browser.