1.编译环境
FFmpeg 4.1
NDK android-ndk-r15c
2、错误1少文件
makefile:2: ffbuild/config.mak: no such file or directory
解决方法：
先不要执行make和make install，第一步先在ffmpeg-4.1下执行./configure，该命令会自动生成缺少的文件
3.错误2
../libavutil/libm.h:62: error: static declaration of 'lrint' follows non-static declaration
../libavutil/libm.h:69: error: static declaration of 'lrintf' follows non-static declaration
../libavutil/libm.h:76: error: static declaration of 'round' follows non-static declaration
../libavutil/libm.h:83: error: static declaration of 'roundf' follows non-static declaration
./libavutil/libm.h:90: error: static declaration of 'truncf' follows non-static declaration
解决方法：
config.h搜索lrint、lrintf、round、roundf等对应的字符
#define HAVE_LLRINT 1
#define HAVE_LLRINTF 1
#define HAVE_LRINT 1
#define HAVE_LRINTF 1
#define HAVE_ROUND 1
#define HAVE_ROUNDF 1
将对应的值改为1即可
3.错误3
ffmpeg yasm not found, use --disable-yasm
解决方法：
下载yasm ，重命名为yasm.exe ，放到MinGW\bin 目录下
4.错误4
libavformat/os_support.c: In function 'ff_gai_strerror':
libavformat/os_support.c:194:10: error: 'ERROR_NOT_ENOUGH_MEMORY' undeclared (first use in this function)
解决方法：
打开libavformat/os_support.h 文件，在其中增加 #include <winerror.h>
5.错误5
[install-libavdevice-static] Error 127
