Search the ffmpeg source code, and you can find that the prompt is printed in the configure file. The source code is as follows:

enabled openssl           && { use_pkg_config openssl openssl/ssl.h OPENSSL_init_ssl ||
                               check_lib openssl/ssl.h OPENSSL_init_ssl -lssl -lcrypto ||
                               use_pkg_config openssl openssl/ssl.h SSL_library_init ||
                               check_lib openssl/ssl.h SSL_library_init -lssl -lcrypto ||
                               check_lib openssl/ssl.h SSL_library_init -lssl32 -leay32 ||
                               check_lib openssl/ssl.h SSL_library_init -lssl -lcrypto -lws2_32 -lgdi32 ||
                               die "ERROR: openssl not found"; }

You can find that ffmpeg is trying OpenSSL one by one. My config The log shows that the last one has been checked, but OpenSSL is still not found.

The reason is that I am using a newer openssl library, the old openssl library uses ‘SSL_library_init’ to initialize, the newer openssl version uses ‘OPENSSL_init_ssl’ to initialize. The new version of openssl uses ‘OPENSSL_init_ssl’ to initialize, and because it does not pass the check, this error is reported here.

Solution:

Add a line to check ‘check_lib openssl/ssl.h OPENSSL_init_ssl -lssl -lcrypto ‘ and it will pass, above is what I have added.