I expected there to be a lot more code here... were the codecs themselves merged before? Is it using a library that's doing all the heavy lifting that was merged before?
Also is using "hard-coded" methods like is_av1 a best practice in C, as opposed to something like codec == "av1" or member?(codec, "av1") etc. I have to assume it has to do with minimizing dynamic memory allocations... (pardon the rudimentary C questions, I haven't coded in C in 20 years)