Rk3399 solves the problem that opencv crossover cannot save video using ffmpeg

OPENCV Cross cannot be used FFMPEG The main reason for saving videos is ：opencv Even if you don’t use ffmpeg It can also be compiled normally videoio modular , So the problem is compiling opencv when videoio Module not found ffmpeg, Here’s the picture ：

resolvent ：

1、 To write toolchain.cmake, among ffmpeg Installed to /opt/sysroot/usr, also /opt/sysroot/usr/lib/pkgconfig There is ffmpeg relevant pc file .

set( CMAKE_SYSTEM_NAME Linux )
set( CMAKE_SYSTEM_PROCESSOR aarch64 )
set( CMAKE_C_COMPILER aarch64-linux-gnu-gcc )
set( CMAKE_CXX_COMPILER aarch64-linux-gnu-g++ )

set( CMAKE_FIND_ROOT_PATH "/opt/sysroot/usr")
set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )
set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

2、 install ：pkg-config

apt-get install pkg-config

3、 add to PKG_CONFIG_PATH environment variable

export PKG_CONFIG_PATH=/opt/sysroot/usr/lib/pkgconfig

echo $PKG_CONFIG_PATH // Check whether the settings are effective 

4、 perform cmake-gui, choice toolchain.cmake Cross compile file compilation , And check the compile option

5、cmake-gui adopt Add Entry Button to add OPENCV_ENABLE_PKG_CONFIG, choose bool type , tick .

 6、 Click again Configure, You can see ffmpeg Found ：

7、 And then click generate ==> make ==> make install; Finish compiling .