Error LNK2001: unresolved external symbol

after I type
```
python setup.py build_ext --cmake-args="-DCMAKE_TOOLCHAIN_FILE=[path to vcpkg]/scripts/buildsystems/vcpkg.cmake"
```
I found **error** in powershell
error LNK2001: unresolved external symbol av_parser_parse2 [D:\h264decoder\h264decoder-master\bu
ild\temp.win-amd64-3.7\Release\h264decoder.vcxproj]

**How to fix it?**
