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2015-11-26 11:40:45 -0600	answered a question	VideoCapture open starts many threads I found this line of code in the github repositories. https://github.com/Itseez/opencv/blob... Changing this line will determine how many threads get created when using ffmpeg. I changed this to two in my application. It is surprising that this is no parameter.
2015-11-26 11:38:36 -0600	commented question	VideoCapture open starts many threads Yes, I understand that it is to make the decoding process faster. But decoding one video creates many threads. I can imagine quite a few use cases where you do not want to use your entire computational power to decode the video. It just seemed a little bit strange to have this as a default behaviour.
2015-11-19 01:19:32 -0600	commented question	VideoCapture open starts many threads I'm sorry, ubuntu 14.04 and opencv 2.4.11
2015-11-18 12:25:23 -0600	received badge	● Student (source)
2015-11-18 12:22:43 -0600	asked a question	VideoCapture open starts many threads Hy, I've noticed that when opening a video file using the VideoCapture class (in C++), about eight new threads are created. As I need 7 video files simultaneously this results in about 50 threads running. I was wondering why this happens and what the threads do (because I can't find anything about this online). Thanks
2015-11-09 02:02:55 -0600	commented question	installing opencv Hy, I allready tried that, and it makes the build succeed. However, I need to be able to read video files in formats such as x264 and as far as I tested it, this was no longer possible.
2015-11-08 09:04:13 -0600	asked a question	installing opencv Hy, I need OpenCV for a project I'm working on, however so far I've not been able to successfully build it. I've been trying numorous build guides and haven't found any solution yet. The make process always fails with the errors listed in the code section below. I found several posts online of people having the same issue. However I've tried all these and none of them seemed to work for me. I originally was trying to build an older version of opencv 2.4.9 because some of the code I'm using is using the older opencv. However, even with the new version 3.0 it is not working for me. Does anyone have any suggestion what I might try? I will also include the result of the cmake configuration. Thanks. /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:317:36: error: ‘avcodec_free_frame’ was not declared in this scope avcodec_free_frame(&picture); ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp: In member function ‘bool CvCapture_FFMPEG::open(const char)’: /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:632:43: error: ‘avcodec_alloc_frame’ was not declared in this scope picture = avcodec_alloc_frame(); ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:635:41: error: ‘PIX_FMT_BGR24’ was not declared in this scope avpicture_get_size( PIX_FMT_BGR24, ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp: In member function ‘bool CvCapture_FFMPEG::retrieveFrame(int, unsigned char, int, int, int, int)’: /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:738:67: error: ‘PIX_FMT_RGB24’ was not declared in this scope avpicture_fill((AVPicture)&rgb_picture, rgb_picture.data[0], PIX_FMT_RGB24, ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:756:17: error: ‘PIX_FMT_BGR24’ was not declared in this scope PIX_FMT_BGR24, ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp: In function ‘AVFrame* icv_alloc_picture_FFMPEG(int, int, int, bool)’: /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:1110:35: error: ‘avcodec_alloc_frame’ was not declared in this scope picture = avcodec_alloc_frame(); ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:1113:33: error: ‘PixelFormat’ was not declared in this scope size = avpicture_get_size( (PixelFormat) pix_fmt, width, height); ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:1122:38: error: expected ‘)’ before ‘pix_fmt’ (PixelFormat) pix_fmt, width, height); ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp: At global scope: /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:1104:47: warning: unused parameter ‘pix_fmt’ [-Wunused-parameter] static AVFrame * icv_alloc_picture_FFMPEG(int pix_fmt, int width, int height, bool alloc) ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp: In function ‘AVStream* icv_add_video_stream_FFMPEG(AVFormatContext*, AVCodecID, int, int, int, double, int)’: /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp:1230:19: error: ‘PixelFormat’ was not declared in this scope c->pix_fmt = (PixelFormat) pixel_format; ^ /home/matthias/Programs/opencv-3.0.0/modules/videoio/src/cap_ffmpeg_impl.hpp: At global scope: /home/matthias/Programs/opencv-3.0.0 ... (more)