Hello everyone. I need to record a video from the camera. I get an error on the check, that is, an empty image is read from the camera. There is a check on the file size:
if (img.empty())
{
std::cout << "empty image" << std::endl;
return 0;
}
My code:
#include <opencv2/opencv.hpp>
#include <iostream>
#include <iostream>
using namespace std;
cv::Mat frame;
int main(int ac, char** av) {
std::cout << cv::getBuildInformation();
cv::VideoCapture cap(0);
if (!cap.isOpened())
{
std::cout << "Can't open the camera" << std::endl;
return -1;
}
cv::Mat img;
cout << "Started video..."<<endl;
while (cap.isOpened())
{
try
{
cap >> img;
if (img.empty())
{
std::cout << "empty image" << std::endl;
return 0;
}
cv::imshow("camera img", img);
if (cv::waitKey(25) == 27)
break;
}
catch( cv::Exception& e )
{
const char* err_msg = e.what();
std::cout << "exception caught: " << err_msg << std::endl;
}
}
return 0;
}
Hi
What’s problem?
I tried to do this, all images are empty and an error is displayed.
What’s result of getBuildInformation()?
1 Like
My logs
General configuration for OpenCV 4.5.2 =====================================
Version control: lf-5.10.72-2.2.0-dirty
Extra modules:
Location (extra): /workdir/contrib/modules
Version control (extra): 4.5.2-dirty
Platform:
Timestamp: 2021-04-12T02:26:40Z
Host: Linux 5.13.0-51-generic x86_64
Target: Linux aarch64
CMake: 3.19.5
CMake generator: Ninja
CMake build tool: ninja
Configuration: Release
CPU/HW features:
Baseline: NEON FP16
required: NEON
disabled: VFPV3
C/C++:
Built as dynamic libs?: YES
C++ standard: 11
C++ Compiler: /workdir/recipe-sysroot-native/usr/bin/aarch64-phytec-linux/aarch64-phytec-linux-g++ (ver 10.2.0)
C++ flags (Release): -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -O2 -pipe -g -feliminate-unused-debug-types -fmacro-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir/recipe-sysroot= -fdebug-prefix-map=/workdir/recipe-sysroot-native= -fvisibility-inlines-hidden -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -DNDEBUG -DNDEBUG
C++ flags (Debug): -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -O2 -pipe -g -feliminate-unused-debug-types -fmacro-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir/recipe-sysroot= -fdebug-prefix-map=/workdir/recipe-sysroot-native= -fvisibility-inlines-hidden -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -g -DDEBUG -D_DEBUG
C Compiler: /workdir/recipe-sysroot-native/usr/bin/aarch64-phytec-linux/aarch64-phytec-linux-gcc
C flags (Release): -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -O2 -pipe -g -feliminate-unused-debug-types -fmacro-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir/recipe-sysroot= -fdebug-prefix-map=/workdir/recipe-sysroot-native= -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -DNDEBUG -DNDEBUG
C flags (Debug): -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -O2 -pipe -g -feliminate-unused-debug-types -fmacro-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir=/usr/src/debug/opencv/4.5.2.imx-r0 -fdebug-prefix-map=/workdir/recipe-sysroot= -fdebug-prefix-map=/workdir/recipe-sysroot-native= -mcpu=cortex-a53 -march=armv8-a+crc+crypto -I/workdir/git/include -fstack-protector-strong -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/workdir/recipe-sysroot -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -g -DDEBUG -D_DEBUG
Linker flags (Release): -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed -Wl,-z,relro,-z,now -Wl,--gc-sections -Wl,--as-needed
Linker flags (Debug): -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed -Wl,-z,relro,-z,now -Wl,--gc-sections -Wl,--as-needed
ccache: NO
Precompiled headers: NO
Extra dependencies: dl m pthread rt
3rdparty dependencies:
OpenCV modules:
To be built: aruco bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
Disabled: freetype world
Disabled by dependency: -
Unavailable: alphamat cnn_3dobj cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv hdf java julia matlab ovis python2 sfm viz
Applications: perf_tests examples apps
Documentation: NO
Non-free algorithms: NO
GUI:
GTK+: YES (ver 3.24.25)
GThread : YES (ver 2.66.7)
GtkGlExt: NO
Media I/O:
ZLib: /workdir/recipe-sysroot/usr/lib/libz.so (ver 1.2.11)
JPEG: /workdir/recipe-sysroot/usr/lib/libjpeg.so (ver 62)
WEBP: /workdir/recipe-sysroot/usr/lib/libwebp.so (ver encoder: 0x020f)
PNG: /workdir/recipe-sysroot/usr/lib/libpng.so (ver 1.6.37)
TIFF: /workdir/recipe-sysroot/usr/lib/libtiff.so (ver 42 / 4.2.0)
JPEG 2000: build (ver 2.4.0)
HDR: YES
SUNRASTER: YES
PXM: YES
PFM: YES
Video I/O:
GStreamer: YES (1.18.5)
v4l/v4l2: YES (linux/videodev2.h)
gPhoto2: YES
Parallel framework: TBB (ver 2021.2 interface 12020)
Trace: YES (with Intel ITT)
Other third-party libraries:
Lapack: NO
Custom HAL: YES (carotene (ver 0.0.1))
Protobuf: /workdir/recipe-sysroot/usr/lib/libprotobuf.so (3.15.2)
Python 3:
Interpreter: /workdir/recipe-sysroot-native/usr/bin/python3-native/python3 (ver 3.9.5)
Libraries: /workdir/recipe-sysroot/usr/lib/libpython3.9.so (ver 3.9.5)
numpy: /workdir/recipe-sysroot/usr/lib/python3.9/site-packages/numpy/core/include (ver undefined - cannot be probed because of the cross-compilation)
install path: lib/python3.9/site-packages/cv2/python-3.9
Python (for build): /workdir/recipe-sysroot-native/usr/bin/python3-native/python3
Install to: /usr
-----------------------------------------------------------------
I don’t know linux but can you open your camera with another application?
I assume that OPENCV is the case, as I execute the gst-launch-1.0 v4l2src device=/dev/video0 command on the video board! video/x-bayer,format=grbg,depth=8,width=1920,height=1080 ! bayer2rgbneon ! videoconvert ! jpegenc ! multifilesink location=live.avi and a video stream is created, everything works!
You can open with three api CAP_GPHOTO2 CAP_V4L or CAP_GSTREAMER
cv::VideoCapture cap(0, cv::CAP_V4L);
If it does not work try another api
1 Like
I tried all the above flags, nothing helps
konstitycii:
gst-launch-1.0
Have you build opencv with test?
please investigate “appsink” and “multifilesink”
gstreamer pipelines in a VideoCapture object must provide an appsink, or else opencv can’t read from the pipeline.