c++ OpenCV 3.4 / FFMPEG 3.4.1录象机和MP4输出文件格式

I'm running on an ARM BeagleBone X-15 Debian machine with Linux Kernel 4.9.35-ti-r44. In my C++ ( Qt 5 ) application, I want to save my cv::Mat frames to an MP4 format video. I have libx264 installed and compiled from scratch both ffmpeg and OpenCv. I can successfully record and view video with MJPEG with the AVI video container type but not MP4. Whenever I try to write an MP4 video, I get run time errors of the form:I'm running on an ARM BeagleBone X-15 Debian ma