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What is H.266 and why is it better than H.265?

Also known as Versatile Video Coding (VVC) and MPEG-I Part 3, H.266 is a video compression standard designed for the latest generations of high-resolution video. It is a successor to the widely used H.265 codec (also known as MPEG-H Part 2) and offers major improvements over that now aging compression scheme.

ContentsWhy is H.266 better than H.265?Better compressionImproved intra-frame predictionImproved inter-frame predictionMore complex encodingBetter support for modern videoWhere is H.266?

H.266 was developed by the Joint Collaborative Team on Video Coding (JCT-VC), a group of video coding experts who began working on the compression standard in 2010.

Why is H.266 better than H.265?

What is H.266 and why is it better than H.265?

The H.266 codec offers major improvements over the H.265 codec, which was first developed in the hazy days of 2013. There are many more improvements that we can cover here, but these are the highlights for consumers.

Better compression

H.266 offers significantly improved compression compared to H.265. The new codec can achieve about 50% more compression than its predecessor. With H.266, a video of the same apparent visual quality would only take up half the space.

Alternatively, a video of the same file size and bitrate could look significantly better. Part of this improvement comes from an increased macroblock size. H.265 allows 64 x 64 pixel macroblocks, while H.266 provides 128 x 128 pixel macroblocks (now called coding tree units or CTUs), allowing for greater coding efficiency at all resolutions.

Improved intra-image prediction

Video compression relies on the prediction of motion between frames. When there is no change in a pixel, a video codec can save space by referencing it rather than reproducing it. Improved motion prediction means improved file size and compression quality.

Besides the improved compression standards in H.266, we also find major improvements in motion prediction and compensation. While H.265 had 35 intra prediction modes, H.266 has an impressive 67.

Improved inter-frame prediction

H.266 brings impressive new tools to improve inter-frame prediction, which enables higher compression rates by essentially determining what the next frame will look like based on its previous one.

H.266 improves upon H.265 by supporting MV resolution as granular as 1/16 luma-samples compared to the 1/4 offered in H.265. That's great, but it's basically a fine-tuning of the compression process.

More complex encoding

It's not all fun and games for H.266. Yes, it offers considerably better compression than its predecessor, but it's also much more complex to encode and a bit more complex to decode. What does this mean concretely? This means that the encoding and decoding process takes a bit longer, making it a less attractive proposition for operating systems and other software.

Better-support for modern video

The world is getting higher and higher resolution, and H.266 supports that. With H.266, video can be encoded up to 8K UHD or 8192 pixels × 4320 pixels. Currently, only a handful of cameras can even output 8K video, and very few monitors can display that kind of resolution. H.266 also supports HDR video and 360-degree videos, two vital modern technologies that were not specifically supported by H.265.

Where is H.266?

H.266 is even less common than H.265. For now, Apple's operating system for iPhone and iPad, iOS, still stores all video files in H.265 format. Microsoft, meanwhile, seems to be more interested in the royalty-free Aomedia Video 1 (AV1) codec and rolled out support for it late last year. AV1 isn't as efficient in compression as H.266, but isn't as locked in on license fees and patents.

One thing is certain:H.266 has not seen as smooth an evolution in terms of adoption as its predecessor. Despite the impressive technology on offer, only time will tell if it will become the world's dominant video compression format.

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