Ok. I was able to compile. The current version of ffmpeg is ver 4.2.2. By default, pthreads is enabled by default.
I ran a test using the version of ffmpeg that comes with dolphin and my compiled version on a 720p 25 minute video using ffmpegs default settings. These are the results.
Dolphin default ffmpeg.
Processed at 43fps and took 17 minutes 46 seconds to convert.
Processed at 250fps using all 8 cores that are in my server and took 3 minutes 2 seconds to convert.
I have to run some more tests, and then see if i can get it to work in cheetah.
There are static versions here also https://www.johnvansickle.com/ffmpeg/ that i am going to check. They are the same version, so unless they were compiled with the --disable-pthreads option, then that version should support pthreads and be the same as the version i compiled.
My compiled version is also much smaller, so i am concerned that it did not compile with static libraries built in. Another thing i will need to check.