OpenCV 3.4.3 - GStream not called when VideoWriting - file

Question

I'd like to succeed writing a file with OpenCV encoding with GStreamer.
Thus I'm using the code :
VideoWriter.open("appsrc ! autovideoconvert ! omxh264enc ! matroskamux ! filesink location=test2.mkv sync=false",
//cv::CAP_GSTREAMER, //set or not, I get the same problem
0, (double)25, //fourcc, fps
cv::Size(1024, 1024),
true);
And my problem :
A video file called appsrc ! autovideoconvert ! omxh264enc ! matroskamux ! filesink location=test2.mkv sync=false is created (rather than test2.mkv), and it is empty. The same problem is corrected and seems to work in the following thread, without any effect for me : Opening a GStreamer pipeline from OpenCV with VideoWriter
I tried, without success :
Add quotes to the file name test2 :
"appsrc ! autovideoconvert ! omxh264enc ! matroskamux ! filesink location=\"test2.mkv\" sync=false" neither
Encode with different format : .flv rather than .mkv
Encode with different codec : omxh265enc rather than omxh264en
I checked :
That GStreamer is well compiled with OpenCV ; the CMake of the OpenCV project outputs :
Video I/O:Video for Windows: YES
DC1394: NO
FFMPEG: YES (prebuilt binaries)
avcodec: YES (ver 57.107.100)
avformat: YES (ver 57.83.100)
avutil: YES (ver 55.78.100)
swscale: YES (ver 4.8.100)
avresample: YES (ver 3.7.0)
GStreamer:
base: YES (ver 1.0)
video: YES (ver 1.0)
app: YES (ver 1.0)
riff: YES (ver 1.0)
pbutils: YES (ver 1.0)
DirectShow: YES
Media Foundation: YES
That FFMpeg is installed on my computer ; for this I used VLC :
File -> Stream -> Add a file then stream
New destination : RTP/MPEG Transport Stream
Profile : Video - H.264 + MP3 (MP4)
Then no error happens ; Note : an error occured with Video - H.265 + MP3
(MP4), but I'm using omxh264enc in my code, not 265
I'm struggled :/ Do you have any idea ?
Thanks a lot :)
Have a good day,
Thibaut
PS - Complete OpenCV CMake output :
Selecting Windows SDK version 10.0.17134.0 to target Windows 10.0.17763.
AVX_512F is not supported by C++ compiler
AVX512_SKX is not supported by C++ compiler
Dispatch optimization AVX512_SKX is not available, skipped
libjpeg-turbo: VERSION = 1.5.3, BUILD = opencv-3.4.3-libjpeg-turbo
Looking for Mfapi.h
Looking for Mfapi.h - found
found Intel IPP (ICV version): 2017.0.3 [2017.0.3]
at: E:/OpenCV/3.4.3/build-cuda92-gstreamer/3rdparty/ippicv/ippicv_win
found Intel IPP IW sources: 2017.0.3
at: E:/OpenCV/3.4.3/build-cuda92-gstreamer/3rdparty/ippicv/ippiw_win
CUDA detected: 9.2
CUDA NVCC target flags: -gencode;arch=compute_30,code=sm_30;-gencode;arch=compute_35,code=sm_35;-gencode;arch=compute_37,code=sm_37;-gencode;arch=compute_50,code=sm_50;-gencode;arch=compute_52,code=sm_52;-gencode;arch=compute_60,code=sm_60;-gencode;arch=compute_61,code=sm_61;-gencode;arch=compute_70,code=sm_70;-D_FORCE_INLINES
Found apache ant: C:/NVPACK/apache-ant-1.8.2/bin/ant.bat (1.8.2)
Could NOT find Matlab (missing: MATLAB_MEX_SCRIPT MATLAB_INCLUDE_DIRS MATLAB_ROOT_DIR MATLAB_LIBRARIES MATLAB_LIBRARY_DIRS MATLAB_MEXEXT MATLAB_ARCH MATLAB_BIN)
VTK is not found. Please set -DVTK_DIR in CMake to VTK build directory, or to VTK install subdirectory with VTKConfig.cmake file
Caffe: NO
Protobuf: NO
Glog: YES
freetype2: NO
harfbuzz: NO
Module opencv_ovis disabled because OGRE3D was not found
No preference for use of exported gflags CMake configuration set, and no hints for include/library directories provided. Defaulting to preferring an installed/exported gflags CMake configuration if available.
Found installed version of gflags: E:/Git/gflags/BUILD-VS2015
Detected gflags version: 2.2.1
Checking SFM deps... FALSE
Module opencv_sfm disabled because the following dependencies are not found: Eigen Glog/Gflags
Excluding from source files list: <BUILD>/modules/dnn/layers/layers_common.avx512_skx.cpp
Tesseract: NO
General configuration for OpenCV 3.4.3 =====================================
Version control: unknown
Extra modules:
Location (extra): E:/OpenCV/3.4.3/opencv_contrib-3.4.3/modules
Version control (extra): unknown
Platform:
Timestamp: 2018-11-07T16:57:18Z
Host: Windows 10.0.17763 AMD64
CMake: 3.12.0-rc2
CMake generator: Visual Studio 14 2015 Win64
CMake build tool: C:/Program Files (x86)/MSBuild/14.0/bin/MSBuild.exe
MSVC: 1900
CPU/HW features:
Baseline: SSE SSE2 SSE3
requested: SSE3
Dispatched code generation: SSE4_1 SSE4_2 FP16 AVX AVX2
requested: SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
SSE4_1 (5 files): + SSSE3 SSE4_1
SSE4_2 (2 files): + SSSE3 SSE4_1 POPCNT SSE4_2
FP16 (2 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
AVX (6 files): + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
AVX2 (11 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
C/C++:
Built as dynamic libs?: YES
C++11: YES
C++ Compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/x86_amd64/cl.exe (ver 19.0.24215.1)
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 /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /MP16 /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 /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /MP16 /MDd /Zi /Ob0 /Od /RTC1
C Compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/x86_amd64/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 /MP16 /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 /MP16 /MDd /Zi /Ob0 /Od /RTC1
Linker flags (Release): /machine:x64 /INCREMENTAL:NO
Linker flags (Debug): /machine:x64 /debug /INCREMENTAL
ccache: NO
Precompiled headers: YES
Extra dependencies: cudart.lib nppc.lib nppial.lib nppicc.lib nppicom.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/v9.2/lib/x64
3rdparty dependencies:
OpenCV modules:
To be built: aruco bgsegm bioinspired calib3d ccalib core cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev datasets dnn dnn_objdetect dpm face features2d flann fuzzy hfs highgui img_hash imgcodecs imgproc java java_bindings_generator line_descriptor ml objdetect optflow phase_unwrapping photo plot python_bindings_generator reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab xfeatures2d ximgproc xobjdetect xphoto
Disabled: js world
Disabled by dependency: -
Unavailable: cnn_3dobj cvv freetype hdf 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 1.2.11)
JPEG: build-libjpeg-turbo (ver 1.5.3-62)
WEBP: build (ver encoder: 0x020e)
PNG: build (ver 1.6.34)
TIFF: build (ver 42 - 4.0.9)
JPEG 2000: build (ver 1.900.1)
OpenEXR: build (ver 1.7.1)
HDR: YES
SUNRASTER: YES
PXM: YES
Video I/O:
Video for Windows: YES
DC1394: NO
FFMPEG: YES (prebuilt binaries)
avcodec: YES (ver 57.107.100)
avformat: YES (ver 57.83.100)
avutil: YES (ver 55.78.100)
swscale: YES (ver 4.8.100)
avresample: YES (ver 3.7.0)
GStreamer:
base: YES (ver 1.0)
video: YES (ver 1.0)
app: YES (ver 1.0)
riff: YES (ver 1.0)
pbutils: YES (ver 1.0)
DirectShow: YES
Media Foundation: YES
Parallel framework: Concurrency
Trace: YES (with Intel ITT)
Other third-party libraries:
Intel IPP: 2017.0.3 [2017.0.3]
at: E:/OpenCV/3.4.3/build-cuda92-gstreamer/3rdparty/ippicv/ippicv_win
Intel IPP IW: sources (2017.0.3)
at: E:/OpenCV/3.4.3/build-cuda92-gstreamer/3rdparty/ippicv/ippiw_win
Custom HAL: NO
Protobuf: build (3.5.1)
NVIDIA CUDA: YES (ver 9.2, CUFFT CUBLAS NVCUVID)
NVIDIA GPU arch: 30 35 37 50 52 60 61 70
NVIDIA PTX archs:
OpenCL: YES (no extra features)
Include path: E:/OpenCV/3.4.3/opencv-3.4.3/3rdparty/include/opencl/1.2
Link libraries: Dynamic load
Python (for build): C:/ProgramData/Miniconda3/python.exe
Java:
ant: C:/NVPACK/apache-ant-1.8.2/bin/ant.bat (ver 1.8.2)
JNI: C:/NVPACK/jdk1.8.0_77/include C:/NVPACK/jdk1.8.0_77/include/win32 C:/NVPACK/jdk1.8.0_77/include
Java wrappers: YES
Java tests: YES
Matlab: NO
Install to: E:/OpenCV/3.4.3/build/install
-----------------------------------------------------------------
Configuring done

Answer 1

Ok, I've eventually found the problem's origin.
By stepping into VideoWriter::open(...) I finally noticed that std::vector backends did not contain any element with "id=CAP_GSTREAMER" -> it did not correctly compile with OpenCV. By investigating more, I discovered it was because I compiled with the x86 version of Gstreamer by mistake (whereas I was building OpenCV for x64).
Have a good day,
Thibaut