Function no_video_encoder_message 

pub fn no_video_encoder_message(
    codec: NativeVideoCodec,
    offered: &[NativeVideoEncoderCapability],
    gpu_output_unavailable: Option<&str>,
) -> String

Why an export of codec has no encoder, and what to do about it.

Names why the GPU path declined (gpu_output_unavailable), what the runtime offers instead (offered), and for H.264 whether OpenH264 is installed.