Nginx on Windows how to know the correct MP4 buffer sizes?

So i do video streaming of large videos 2GB+ in size how do i know what
buffer sizes to use in my nginx config or should i leave it at default ?

location ~ .mp4$ {
#mp4_buffer_size ?;
#mp4_max_buffer_size ?;
limit_rate_after 2m;
limit_rate 1m;
expires max;

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