FFmpeg discovery on Windows

[dzhoshkun]

FFmpeg provides pre-built binaries for Windows. GIFT-Grab's FFmpeg discovery script however relies on pkg-config. For the experimental Windows branch, it'd be good to amend the discovery script in a very simple way to be able to link with the pre-built binaries.

[dzhoshkun]

FFmpeg might be needed to speed up the RGB-to-BGRA conversion for BGRA captures with Epiphan

Downloading the 4.1.3 pre-built dev binaries and running

cmake -A x64 -D CMAKE_BUILD_TYPE=Release -D ZLIB_ROOT="%zlib_root%" -D USE_EPIPHAN_DVI2PCIE_DUO=ON -D ENABLE_NONFREE=ON -D USE_EPIPHANSDK=ON -D PYTHON_INCLUDE_DIRS="%python_include_dirs%" -D PYTHON_LIBRARY="%python_library%" -D BOOST_INCLUDEDIR="%boost_includedir%" -D BOOST_LIBRARYDIR="%boost_librarydir%" -D BUILD_PYTHON=ON -D USE_NUMPY=ON -D FFmpeg_LIBRARY_DIRS="C:/FFmpeg/binaries/ffmpeg-4.1.3-win64-dev/lib" -D FFmpeg_LIBS=avformat,avcodec,avutil,swscale,avfilter -D FFmpeg_INCLUDE_DIRS="C:/FFmpeg/binaries/ffmpeg-4.1.3-win64-dev/include" -D USE_FILES=ON -D USE_HEVC=ON -D ENABLE_NONFREE=ON -D USE_NVENC=ON ../../GIFT-Grab/src

produces #87 related problems on Windows:

[...]
C:\Users\ds18\ws\GIFT-Grab\src\ffmpeg\ffmpeg_video_target.cpp(98): error C2065: 'not': undeclared identifier [C:\Users\ds18\ws\_b\gift-grab\giftgrab.vcxproj]
C:\Users\ds18\ws\GIFT-Grab\src\ffmpeg\ffmpeg_video_target.cpp(98): error C2146: syntax error: missing ')' before identifier '_codec' [C:\Users\ds18\ws\_b\gift-grab\giftgrab.vcxproj]
C:\Users\ds18\ws\GIFT-Grab\src\ffmpeg\ffmpeg_video_target.cpp(98): error C2059: syntax error: ')' [C:\Users\ds18\ws\_b\gift-grab\giftgrab.vcxproj]
[...]

[dzhoshkun]

.dll.a is the extension preferred by GCC for import libraries (.lib is the extension preferred by MSVC)

[dzhoshkun]

• linking FFmpeg static?

[dzhoshkun]

• the encoding example fails with Process finished with exit code -1073740791 (0xC0000409), which might hint at an NVIDIA driver issue
• when running it from the command line, I get:

[nvenc_hevc @ 000002acef991bc0] This encoder is deprecated, use 'hevc_nvenc' instead
[nvenc_hevc @ 000002acef991bc0] Cannot init CUDA

[dzhoshkun]

How to build against FFmpeg:

1. from https://ffmpeg.zeranoe.com/builds/win64/ I've downloaded the "shared" and "dev" pre-builts
2. used the include directories and the import libraries within the dev version for compiling and linking
3. and added a run-time path to the DLL's in the shared version

[dzhoshkun]

#110 (comment) works on the UNT workstation. So possibly #110 (comment) is due to a CUDA/NVIDIA driver installation issue on Hopper.