Function codec_capabilities 

pub fn codec_capabilities() -> NativeCodecCapabilities

Reports the encoders usable by alpha2’s native sinks: the linked FFmpeg’s, and OpenH264 when the user installed it.

A logical codec may have multiple entries, and a hybrid encoder one per way it runs. Hardware entries appear first when they accept the native YUV420P path and their required device is present, then software ones in FFmpeg’s order, then OpenH264; exactly one entry per codec is marked preferred.