is not guaranteed to solve the problem. Search multiple blogs to try to find a solution. Finally clone succeeded. (PS: don’t guarantee success)
http://www.wangxianfeng.cn/wordpress/2018/07/14/git use the common errors in the process of solving/

https://www.cnblogs.com/emmetyang/p/10620819.html attempts to download ffmpeg source problem: (PS: what is the difference between the snapshot version and the version, welcome to the great god taught)

$ git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg
Cloning into 'ffmpeg'...
remote: Counting objects: 570040, done.
remote: Compressing objects: 100% (118805/118805), done.
error: RPC failed; curl 56 OpenSSL SSL_read: SSL_ERROR_SYSCALL, errno 10054
fatal: the remote end hung up unexpectedly
fatal: early EOF
fatal: index-pack failed

first is the problem may be upload size limit, execute the following command:

git config http.postBuffer 524288000

clone again may still error, then you can try

git config http.sslVerify "false"

but then it’s

fatal: not in a git directory

according to the second blog post, use the following command

git config  --global   http.sslVerify "false"

// note that the original blog command was written incorrectly. It should be – global

and then

git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg

just wait.