Performance comparison for marketing

[HyeonuPark]

I'm really excited about this project and want to introduce it to my work. But to do that, I have to persuade my coworkers (and myself). Can we have performance comparison between various encoders of range of encodings, including this project? I think some graphs of bitrate-encoding time tradeoff will be definitely helpful.

[rzumer]

Related: #648

[lu-zero]

@HyeonuPark do you have a specific use-case in mind? We are currently looking for samples we can use to tune some details of the encoder, so the timing would be great :)

[HyeonuPark]

To be specific, what I need is a realtime encoder with dynamic bitrate limit, usually hundreds of kbps. I know it's hard for AV1, but it will be awesome if rav1e can be used under such requirements.

[barrbrain]

FYI, I adapted https://github.com/Kagami/av1-bench to try to match encoding time and bit-rate for still images. Just one luma-only metric does not tell the whole story but this gives an indication of comparable presets.