I’ve tried this on WSL. If you also add libavdevice a to ocv_check_modules as below then it should compile without any errors.
set(_required_ffmpeg_libraries libavcodec libavformat libavutil libswscale libavdevice)
set(_used_ffmpeg_libraries ${_required_ffmpeg_libraries})
if(NOT HAVE_FFMPEG AND PKG_CONFIG_FOUND)
ocv_check_modules(FFMPEG libavcodec libavformat libavutil libswscale libavdevice)
What I can’t test as WSL doesn’t have drivers to access the webcam is what happens when you setOPENCV_FFMPEG_CAPTURE_OPTIONS=input_format;v4l2VideoCapture cap("/dev/video0", CAP_FFMPEG);
data
August 5, 2022, 9:56am
16
Thanks, I did change the files accordingly. The build process went without errors. Then I set OPENCV_FFMPEG_CAPTURE_OPTIONS like this:
setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", "input_format;v4l2", 1);
and accessed the camera like this:
cv::VideoCapture d_reader(fname, cv::VideoCaptureAPIs::CAP_FFMPEG);
then unfortunately I got the following error message:
$./run /dev/video0
[video4linux2,v4l2 @ 0x564b8b62c380] No such input format: v4l2.
Did I set it correctly or does this mean the way fixing ffmpeg under Windows you suggested can’t be transferred to Ubuntu?
I could not say for sure without testing myself, there may be other arguments which need to be set, have you tried stepping through CvCapture_FFMPEG::open() to see which FFmpeg call fails and what the error code is?
ffmpeg -f v4l2 -i /dev/video0
or similar.
data
August 5, 2022, 10:41am
18
I am not quite sure how to do that, but I can provide you the Debug Log:
Debug Log
$ ./run /dev/video0
[DEBUG:0@0.000] global /home/nvidiapc/openCV/opencv/modules/highgui/src/backend.cpp (120) createDefaultUIBackend UI: Initializing backend...
[DEBUG:0@0.000] global /home/nvidiapc/openCV/opencv/modules/highgui/src/registry.impl.hpp (87) UIBackendRegistry UI: Builtin backends(3): GTK(1000); GTK3(990); GTK2(980) + BUILTIN(QT5)
[DEBUG:0@0.000] global /home/nvidiapc/openCV/opencv/modules/highgui/src/registry.impl.hpp (112) UIBackendRegistry UI: Available backends(3): GTK(1000); GTK3(990); GTK2(980) + BUILTIN(QT5)
[ INFO:0@0.000] global /home/nvidiapc/openCV/opencv/modules/highgui/src/registry.impl.hpp (114) UIBackendRegistry UI: Enabled backends(3, sorted by priority): GTK(1000); GTK3(990); GTK2(980) + BUILTIN(QT5)
[DEBUG:0@0.000] global /home/nvidiapc/openCV/opencv/modules/highgui/src/backend.cpp (78) createUIBackend UI: trying backend: GTK (priority=1000)
[DEBUG:0@0.000] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (220) getPluginCandidates UI: GTK plugin's glob is 'libopencv_highgui_gtk*.so', 1 location(s)
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (230) getPluginCandidates - /usr/local/lib: 0
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (234) getPluginCandidates Found 0 plugin(s) for GTK
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/backend.cpp (78) createUIBackend UI: trying backend: GTK3 (priority=990)
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (220) getPluginCandidates UI: GTK3 plugin's glob is 'libopencv_highgui_gtk3*.so', 1 location(s)
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (230) getPluginCandidates - /usr/local/lib: 0
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (234) getPluginCandidates Found 0 plugin(s) for GTK3
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/backend.cpp (78) createUIBackend UI: trying backend: GTK2 (priority=980)
[DEBUG:0@0.001] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (220) getPluginCandidates UI: GTK2 plugin's glob is 'libopencv_highgui_gtk2*.so', 1 location(s)
[DEBUG:0@0.002] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (230) getPluginCandidates - /usr/local/lib: 0
[DEBUG:0@0.002] global /home/nvidiapc/openCV/opencv/modules/highgui/src/plugin_wrapper.impl.hpp (234) getPluginCandidates Found 0 plugin(s) for GTK2
[DEBUG:0@0.002] global /home/nvidiapc/openCV/opencv/modules/highgui/src/backend.cpp (106) createUIBackend UI: fallback on builtin code: QT5
[DEBUG:0@0.146] global /home/nvidiapc/openCV/opencv/modules/videoio/src/videoio_registry.cpp (197) VideoBackendRegistry VIDEOIO: Builtin backends(7): FFMPEG(1000); GSTREAMER(990); INTEL_MFX(980); V4L2(970); CV_IMAGES(960); CV_MJPEG(950); UEYE(940)
[DEBUG:0@0.146] global /home/nvidiapc/openCV/opencv/modules/videoio/src/videoio_registry.cpp (221) VideoBackendRegistry VIDEOIO: Available backends(7): FFMPEG(1000); GSTREAMER(990); INTEL_MFX(980); V4L2(970); CV_IMAGES(960); CV_MJPEG(950); UEYE(940)
[ INFO:0@0.146] global /home/nvidiapc/openCV/opencv/modules/videoio/src/videoio_registry.cpp (223) VideoBackendRegistry VIDEOIO: Enabled backends(7, sorted by priority): FFMPEG(1000); GSTREAMER(990); INTEL_MFX(980); V4L2(970); CV_IMAGES(960); CV_MJPEG(950); UEYE(940)
[video4linux2,v4l2 @ 0x5605da05dd40] No such input format: v4l2.
Yes, I was able to access the Webcam with cv::VideoCapture("/dev/video0") before.
I’d say that’s as far as we can go then without stepping through the code to see where the error is, sorry.
data
August 12, 2022, 4:09pm
20
Hello @cudawarped ,
I performed a quick test and it appears that you can retrieve the raw encoded MJPEG data from directshow using CAP_FFMPEG if you slightly modify the source and link OpenCV against libavdevice. You need to add
avdevice_register_all();
to void CvCapture_FFMPEG::init() and
#include <libavdevice/avdevice.h>.
Unfortunatley this means you need to build OpenCV against FFMPEG libs and not use the precompiled dll - opencv_videoio_ffmpegxxx_64.dll.
Once the modification is in place you simply ne…
Build
OS: Windows 10 Pro (21H2)
CMake Config
General configuration for OpenCV 4.6.0 =====================================
Version control: unknown
Extra modules:
Location (extra): C:/Users/NvidiaPC/OpenCV/opencv_contrib-4.6.0/modules
Version control (extra): unknown
Platform:
Timestamp: 2022-08-11T11:28:03Z
Host: Windows 10.0.19044 AMD64
CMake: 3.24.0-rc5
CMake generator: Visual Studio 17 2022
CMake build tool: C:/Program Files/Microsoft Visual Studio/2022/Community/MSBuild/Current/Bin/amd64/MSBuild.exe
MSVC: 1932
Configuration: Release
CPU/HW features:
Baseline: SSE SSE2 SSE3
requested: SSE3
Dispatched code generation: SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
requested: SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
SSE4_1 (18 files): + SSSE3 SSE4_1
SSE4_2 (2 files): + SSSE3 SSE4_1 POPCNT SSE4_2
FP16 (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
AVX (5 files): + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
AVX2 (33 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
AVX512_SKX (8 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX
C/C++:
Built as dynamic libs?: YES
C++ standard: 11
C++ Compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.32.31326/bin/Hostx64/x64/cl.exe (ver 19.32.31332.0)
C++ flags (Release): /DWIN32 /D_WINDOWS /W4 /GR /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:fast /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /MP /MD /O2 /Ob2 /DNDEBUG
C++ flags (Debug): /DWIN32 /D_WINDOWS /W4 /GR /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:fast /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /MP /MDd /Zi /Ob0 /Od /RTC1
C Compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.32.31326/bin/Hostx64/x64/cl.exe
C flags (Release): /DWIN32 /D_WINDOWS /W3 /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:fast /MP /MD /O2 /Ob2 /DNDEBUG
C flags (Debug): /DWIN32 /D_WINDOWS /W3 /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:fast /MP /MDd /Zi /Ob0 /Od /RTC1
Linker flags (Release): /machine:x64 /INCREMENTAL:NO
Linker flags (Debug): /machine:x64 /debug /INCREMENTAL
ccache: NO
Precompiled headers: NO
Extra dependencies: cudart_static.lib nppc.lib nppial.lib nppicc.lib nppidei.lib nppif.lib nppig.lib nppim.lib nppist.lib nppisu.lib nppitc.lib npps.lib cublas.lib cufft.lib -LIBPATH:C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v11.7/lib/x64
3rdparty dependencies:
OpenCV modules:
To be built: aruco barcode bgsegm bioinspired calib3d ccalib core cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev 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 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab wechat_qrcode world xfeatures2d ximgproc xobjdetect xphoto
Disabled: -
Disabled by dependency: -
Unavailable: alphamat cvv freetype hdf java julia matlab ovis python2 python3 sfm viz
Applications: tests perf_tests apps
Documentation: NO
Non-free algorithms: NO
Windows RT support: NO
GUI:
Win32 UI: YES
VTK support: NO
Media I/O:
ZLib: build (ver 1.2.12)
JPEG: build-libjpeg-turbo (ver 2.1.2-62)
WEBP: build (ver encoder: 0x020f)
PNG: build (ver 1.6.37)
TIFF: build (ver 42 - 4.2.0)
JPEG 2000: build (ver 2.4.0)
OpenEXR: build (ver 2.3.0)
HDR: YES
SUNRASTER: YES
PXM: YES
PFM: YES
Video I/O:
DC1394: NO
FFMPEG: YES (prebuilt binaries)
avcodec: YES (58.134.100)
avformat: YES (58.76.100)
avutil: YES (56.70.100)
swscale: YES (5.9.100)
avresample: YES (4.0.0)
GStreamer: NO
DirectShow: YES
Media Foundation: YES
DXVA: YES
Parallel framework: Concurrency
Trace: YES (with Intel ITT)
Other third-party libraries:
Intel IPP: 2020.0.0 Gold [2020.0.0]
at: C:/Users/NvidiaPC/OpenCV/build/3rdparty/ippicv/ippicv_win/icv
Intel IPP IW: sources (2020.0.0)
at: C:/Users/NvidiaPC/OpenCV/build/3rdparty/ippicv/ippicv_win/iw
Lapack: NO
Eigen: NO
Custom HAL: NO
Protobuf: build (3.19.1)
NVIDIA CUDA: YES (ver 11.7, CUFFT CUBLAS FAST_MATH)
NVIDIA GPU arch: 86
NVIDIA PTX archs:
cuDNN: NO
OpenCL: YES (NVD3D11)
Include path: C:/Users/NvidiaPC/OpenCV/opencv-4.6.0/3rdparty/include/opencl/1.2
Link libraries: Dynamic load
Python (for build): NO
Java:
ant: NO
JNI: NO
Java wrappers: NO
Java tests: NO
Install to: C:/Users/NvidiaPC/OpenCV/build/install
-----------------------------------------------------------------
Configuring done
Generating done
Unfortunately it does not work on first try:
cv::VideoCapture cam(0, cv::VideoCaptureAPIs::CAP_FFMPEG);
leads to the following error message:
Error Message :
OpenCV: terminate handler is called! The last OpenCV error is:
OpenCV(4.6.0) Error: Assertion failed (size.width>0 && size.height>0) in cv::imshow, file ...\OpenCV\opencv-4.6.0\modules\highgui\src\window.cpp, line 967
data
August 17, 2022, 10:22am
21
Also it is not clear to me how you set these variable in Windows. Is it via UI or PowerShell? Although in both cases the format of this variable seems strange to me.
and yes the format is strange because the one who implemented that in OpenCV decided that it needs to be strange. there is probably no reason for it.
1 Like
data
August 19, 2022, 12:56pm
24
Hi,
Thank you
Sure thing, see this post
data
August 19, 2022, 1:53pm
26
Thanks for the quick reply
I extracted the Build and created an directory /cmake containing the mentioned .cmake file.
FFMPEG: Downloading opencv_videoio_ffmpeg.dll from https://raw.githubusercontent.com/opencv/opencv_3rdparty/65ec04d4573dcdfa4531f0b9e67f35d8ffff873e/ffmpeg/opencv_videoio_ffmpeg.dll
FFMPEG: Downloading opencv_videoio_ffmpeg_64.dll from https://raw.githubusercontent.com/opencv/opencv_3rdparty/65ec04d4573dcdfa4531f0b9e67f35d8ffff873e/ffmpeg/opencv_videoio_ffmpeg_64.dll
FFMPEG: Downloading ffmpeg_version.cmake from https://raw.githubusercontent.com/opencv/opencv_3rdparty/65ec04d4573dcdfa4531f0b9e67f35d8ffff873e/ffmpeg/ffmpeg_version.cmake
I don’t use the GUI.
How did you set the CMake flag OPENCV_FFMPEG_USE_FIND_PACKAGE=ON?
How did you set CMAKE_PREFIX_PATH or FFMPEG_DIR environmental variables?
data
August 19, 2022, 2:11pm
28
I used the Environment Editor for the varibles
Same here, althought i wasn’t sure if this would actually work.
Inside CMake?
data:
How do you use cmake?
From the command line, that way I canset FFMPEG_DIR=...cmake.exe ... .. OPENCV_FFMPEG_USE_FIND_PACKAGE=ON
Although I would have thought you should be able to achieve the same thing in the GUI if you add OPENCV_FFMPEG_USE_FIND_PACKAGE using Add Entry not Environment. The only problem is you then have to configure again and it might not pick up this additional variable.
data
August 19, 2022, 2:33pm
30
cudawarped:
Inside CMake?
Yes inside cmake-gui you can edit environment variables. I previously set the varibles in the Windows UI for environmental variables, which led them to appear in the Environment Editor of Cmake-gui. With cmd set you can achieve the same.
This might be the issue. I tried opening the gui with cmd, but added the OPENCV_FFMPEG_USE_FIND_PACKAGE=ON Flag. No difference.
Works for me in the GUI, if I add OPENCV_FFMPEG_USE_FIND_PACKAGE as a boolean using Add Entry, even if I press configure twice.
I configured first without the setting OPENCV_FFMPEG_USE_FIND_PACKAGE and got the default downloaded version of FFmpeg
FFMPEG: YES (prebuilt binaries)
avcodec: YES (58.134.100)
avformat: YES (58.76.100)
avutil: YES (56.70.100)
swscale: YES (5.9.100)
avresample: YES (4.0.0)
then I set OPENCV_FFMPEG_USE_FIND_PACKAGE using Add Entry, pressed configure again and CMake picked up my FFmpeg install
FFMPEG: YES (find_package)
avcodec: YES (59.18.100)
avformat: YES (59.16.100)
avutil: YES (57.17.100)
swscale: YES (6.4.100)
data
August 19, 2022, 2:58pm
32
Sorry, yes it works, but do you also have these errors?:
CMake Warning at modules/videoio/cmake/detect_ffmpeg.cmake:6 (find_package):
C:/Users/NvidiaPC/FFMPEG_BUILD/cmake/ffmpeg-config.cmake
but it set FFMPEG_FOUND to FALSE so package “FFMPEG” is considered to be
Did you see the above in the output, did you download the FFmpeg build?
data
August 22, 2022, 9:01am
34
I downloaded and extracted the FFmpeg Build like you described in the other post.(find_package) instead of the (prebuild binaries):
FFMPEG: YES (find_package)
avcodec: YES (58.134.100)
avformat: YES (58.76.100)
avutil: YES (56.70.100)
swscale: YES (5.9.100)
avresample: YES (4.0.0)
