>I'll also point out that the reported MOS scores have several oddities, like an 8mbps av1 stream being rates lower than it's own 6mbps stream.
That reminds me of the old, hilariously broken ffmpeg AAC encoder where increasing the bitrate decreased the quality after a certain point, at least in my tests. So although my guess at what would be causing weird stuff like this would certainly be bad testing methodology by BBC rather than a quirk in the encoder, there's a non-zero chance that I'd be wrong.
That reminds me of the old, hilariously broken ffmpeg AAC encoder where increasing the bitrate decreased the quality after a certain point, at least in my tests. So although my guess at what would be causing weird stuff like this would certainly be bad testing methodology by BBC rather than a quirk in the encoder, there's a non-zero chance that I'd be wrong.