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Comment by Osiris | Hacker News Reader

> Compared to x264, it offers 15-20% better compression rates, but is ~5x slower.

This is interesting. H.265 and VP9 claim to use nearly 50% lower bitrate at the same quality level as H.264. Is this just a case of x264 being really well optimized that VP9 can only compress 20% better at the same quality?

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A few reasons: (1) x264 is better optimized for metrics, especially PSNR. Example: removing --tune=psnr gives x264 a 12% decrease in its PSNR score in this test set (!); (2) the resolution here is only 360p, and as resolution goes down, so do gains versus codecs optimized for high-resolution content (like HEVC/VP9); (3) this article uses inverse notation, so instead of "H264 uses 50% more bits than X for same quality" (which is the same as X using 33% less bits than H264 for same quality), this article says "Eve uses 15-20% less bits than x264 for same quality".

> (2) the resolution here is only 360p

This is really the biggest one. Google has been using low-resolution test material for VP10, and back in September [1] were claiming only a 10% reduction over VP9 on CIF resolution material (352x288). Neither VP9 nor HEVC get anywhere close to their claimed 50% improvement over H.264 on this kind of material (both save around 20%).

So seeing 7...8% reductions at similar resolutions just from a better encoder is pretty significant. It would be great to see how it scales beyond 720p.

[1] https://www.youtube.com/watch?v=gkz1ZvejmEc&list=PLQLpBN3oI7... (sorry for the YouTube link, I couldn't find slides).

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