Am a bit frustrated that the docs have been inaccurate for over 3 years apparently.
You need to use everything for the INIT... use all of the parameters not just the oauth_* ones The following php curl code got me past the error 32
Edit: The above is also true for APPEND and FINALIZE. Please check my twitter bot for info.
$media_api = "https://upload.twitter.com/1.1/media/upload.json";