Improved intraframe motion prediction
Video compression relies on predicting motion between frames. When there’s no change in a pixel, a video codec can save space by referencing it, rather than reproducing it. So improved motion prediction means improved file size and compression quality. Alongside the improved compression standards in H.265, we also find major improvements in motion prediction and compensation.
Improved intraframe prediction
Video compression also benefits from analyzing “movement” within individual frames, allowing single frames of video to be compressed more efficiently. This can be achieved by essentially describing pixels with a mathematical function rather than actual pixel values. The function takes up less space than pixel data, shrinking file size. However, the codec must support a sufficiently advanced mathematical function for this technique to be truly useful. H.265’s intraframe prediction function is far more detailed than H.264’s, allowing for 33 directions of motion over H.264’s nine directions.
H.265 uses tiles and slices which can be decoded independently from the rest of a frame. This means that the decoding process can be split up across multiple parallel process threads, taking advantage of more efficient decoding opportunities on now-standard multi-core processors. With video resolutions getting higher, this kind of improved efficiency is required to decode video at a watchable pace on lower-end hardware.
Higher maximum frame size
The world is getting higher-res, and H.265 supports that. With H.265, video can be encoded at up to 8K UHD or 8192 pixels × 4320 pixels. Currently, only a handful of cameras can even produce 8K video, and very few monitors can display that kind of resolution. But just as HD is today’s standard, we can expect 4K and eventually 8K to rise to similar prominence eventually.