High Efficiency Video Coding

High Efficiency Video Coding, HEVC, H265 and MPEG-H Part 2, is a video compression standard designed as a successor to the widely used Advanced Video Coding (AVC, H264, or MPEG-4 Part 10).

Video Compression

AVC, H264 bitstream is a block-oriented standard with motion competition by breaking an image down into macroblocks of pixel squares. AVC uses the integer discrete cosine transform (DCT) with macroblocks of 4×4 and 8×8 block sizes or as large as 16×16 pixels. These can be further divided into transform and prediction blocks.
HEVC, h265 bitstream is also a block-oriented standard by breaking an image down into coding tree units (CTUs) of pixel squares. HEVC uses integer DCT and DST transforms with varied block sizes between 4×4 and 32×32 and is up to 64×64 pixels.

Source/Reference

• https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding 
• https://www.unifore.net/ip-video-surveillance/difference-between-h-265-and-h-265-video-compression.html
• https://site.brid.tv/h-264-vs-h-265-what-they-are-and-which-one-is-better/