opencv videocapture无法打开MJPEG流 [英] opencv videocapture can't open MJPEG stream
问题描述
Opencv 2.4.9:VideoCapture无法打开MJPG-streamer:
the Opencv 2.4.9: VideoCapture cann't open the MJPG-streamer:
VideoCapture cap;
cap.open("http://127.0.0.1:8080/?action=stream&type=.mjpg");
if (!cap.isOpened()) // if not success, exit program
{
cout << "Cannot open the video cam" << endl;
return -1;
}
我可以看到该视频使用了gst-launch.并且我进行了很多搜索，例如这，并尝试了
I can see the video use gst-launch. and I have searched a lot,like this and tried the fifo like this,but still cann't open it.
然后我想调试到opencv，用CMAKE_BUILD_TYPE = DEBUG编译opencv，但是我的GDB无法进入开放功能.知道吗?
then I want to debug into opencv,compile opencv with CMAKE_BUILD_TYPE=DEBUG, but my GDB just cann't step into the open function.any idea?
我的makefile:
my makefile:
OpencvDebugLibDir=/home/ry/lib
CFLAGS = -g -I$(OpencvDebugLibDir)/include/opencv -I$(OpencvDebugLibDir)
LIBS = $(OpencvDebugLibDir)/lib/*.so
target : main.cpp
g++ $(CFLAGS) $(LIBS) -o $@ $<
顺便说一句，我在opensue13.1中，使用相同的代码，我可以在win 7中打开视频.
by the way, I am in opensue13.1, with the same code,I can open the video in win 7.
谢谢.
更新 现在我可以进入某些功能，例如:imshow，waitKey，但不能进入其他功能，例如:imread，namedWindow，它显示:
Update now I can step into some function like:imshow,waitKey, but I can not step into others like:imread,namedWindow,it shows:
29 image = cv::imread(name);
(gdb) s
std::allocator<char>::allocator (this=0x7fffffffdc7f)
at /usr/src/debug/gcc-4.8.1-20130909/obj-x86_64-suse-linux/x86_64-suse-linux/libstdc++-v3/include/bits/allocator.h:113
113 allocator() throw() { }
test4.cpp:
test4.cpp:
#include <stdio.h>
#include <opencv2/opencv.hpp>
using namespace cv;
int main(int argc, char** argv )
{
Mat image;
image = imread( "LinuxLogo.jpg", 1 );
if ( !image.data )
{
printf("No image data \n");
return -1;
}
namedWindow("Display Image", CV_WINDOW_AUTOSIZE );
imshow("Display Image", image);
waitKey(0);
return 0;
}
我的makefile:
my makefile:
OpencvDebugLibDir=/home/ry/lib
CFLAGS=-g -I$(OpencvDebugLibDir)/include/opencv -I$(OpencvDebugLibDir)
LIBS=$(OpencvDebugLibDir)/lib
test4:test4.cpp
g++ $(CFLAGS) -o $@ $< -L$(LIBS) -lopencv_highgui -lopencv_core -Wl,-rpath=/home/ry/lib/lib
运行gdb:
gdb test4 -d /home/ry/learn/opencv/install/OpenCV/opencv-2.4.9/modules/core/src -d /home/ry/learn/opencv/install/OpenCV/opencv-2.4.9/modules/highgui/src
推荐答案
opencv videocapture无法打开MJPEG流，因为我没有编译支持FFMPEG的opencv. 详细信息: 当cmake opencv时:
opencv videocapture can't open MJPEG stream,because I don't compile opencv with FFMPEG support. detail: when cmake the opencv:
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D BUILD_SHARED_LIBS=ON -D WITH_TBB=ON -D WITH_OPENMP=ON -D WITH_OPENCL=ON -D WITH_CUDA=ON -D WITH_GTK=ON -D BUILD_NEW_PYTHON_SUPPORT=ON -D WITH_V4L=ON -D INSTALL_C_EXAMPLES=OFF -D INSTALL_PYTHON_EXAMPLES=OFF -D BUILD_EXAMPLES=OFF -D WITH_QT=ON -D WITH_OPENGL=ON -D BUILD_JPEG=ON -D BUILD_PNG=ON -D BUILD_JASPER=ON -D BUILD_ZLIB=ON -D WITH_JPEG=ON -D WITH_PNG=ON -D WITH_JASPER=ON -D WITH_ZLIB=ON -D WITH_OPENEXR=OFF ..
您得到类似的东西:
FFMPEG: NO
-- codec: NO
-- format: NO
-- util: NO
-- swscale: NO
-- gentoo-style: NO
因此cmake找不到FFMPEG.我应该在我的机器(Opensuse 13.1)中安装libffmpeg-devel，然后pkg-config可以找到FFMPEG，您可以使用以下命令进行检查:
so the cmake don't find the FFMPEG. I should install libffmpeg-devel in my machine(Opensuse 13.1),then the pkg-config can find FFMPEG,you can check with this:
pkg-config --list-all | grep libavcodec
然后再次运行以上cmake命令，我得到:
then run the above cmake command again, I get:
FFMPEG: YES
-- codec: YES (ver 55.69.100)
-- format: YES (ver 55.48.100)
-- util: YES (ver 52.92.100)
-- swscale: YES (ver 2.6.100)
-- gentoo-style: YES
制作，我得到了能够打开MJPG_Streamer的opencv视频捕捉.
make,and I get the opencv videocapture able to open MJPG_Streamer.
PS:找出原因，我编译了一个调试版本的opencv，并进入了VideoCapture的open函数，并在"opencv-2.4.9/modules/highgui/src/cap"中的icvInitFFMPEG()的构造函数中. cpp:
PS:to find the reason,I compile a debug version opencv,and step into the VideoCapture's open function,and in the construction function of icvInitFFMPEG() in " opencv-2.4.9/modules/highgui/src/cap.cpp ":
#elif defined HAVE_FFMPEG
icvCreateFileCapture_FFMPEG_p = (CvCreateFileCapture_Plugin)cvCreateFileCapture_FFMPEG;
icvReleaseCapture_FFMPEG_p = (CvReleaseCapture_Plugin)cvReleaseCapture_FFMPEG;
icvGrabFrame_FFMPEG_p = (CvGrabFrame_Plugin)cvGrabFrame_FFMPEG;
icvRetrieveFrame_FFMPEG_p = (CvRetrieveFrame_Plugin)cvRetrieveFrame_FFMPEG;
icvSetCaptureProperty_FFMPEG_p = (CvSetCaptureProperty_Plugin)cvSetCaptureProperty_FFMPEG;
icvGetCaptureProperty_FFMPEG_p = (CvGetCaptureProperty_Plugin)cvGetCaptureProperty_FFMPEG;
icvCreateVideoWriter_FFMPEG_p = (CvCreateVideoWriter_Plugin)cvCreateVideoWriter_FFMPEG;
icvReleaseVideoWriter_FFMPEG_p = (CvReleaseVideoWriter_Plugin)cvReleaseVideoWriter_FFMPEG;
icvWriteFrame_FFMPEG_p = (CvWriteFrame_Plugin)cvWriteFrame_FFMPEG;
#endif
它只是跳过这些代码，所以我知道，因为我在编译过程中没有定义HAVE_FFMPEG.
it just step over these code,so I know because I don't have the HAVE_FFMPEG defined in compiling process.
这篇关于opencv videocapture无法打开MJPEG流的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
