Please use the Buffer:encode() method to convert the Buffer binary data with another encoding.
Buffer to string conversion
Buffer can be converted to a string (with the default UTF8 decoder) using the standard Lua function tostring().
Example
-- create a Buffer from string encoded with base64
local buff = sys.Buffer("TMO7w6Q=", "base64")
-- outputs true
print(tostring(buff) == "L��"