H.264 (AVC) 与 H.265 (HEVC)

Technical Foundations

H.265 (HEVC, High Efficiency Video Coding) is the successor to H.264 (AVC, Advanced Video Coding), both developed jointly by ITU-T and ISO/IEC.^[1][2]

The largest structural change is the coding block: where H.264 partitions frames into fixed 16x16 macroblocks, HEVC uses flexible coding tree units up to 64x64 that can be recursively subdivided, letting the encoder allocate bits efficiently across both large flat regions and fine detail.^[1] HEVC also adds more intra-prediction directions and improved motion compensation and entropy coding.

Compression Efficiency

These tools let HEVC achieve approximately the same subjective quality as H.264 at substantially lower bitrates, with figures commonly cited around a 50 percent bitrate reduction, at the cost of significantly higher computational complexity for both encoding and decoding.^[2] HEVC was designed with high resolutions in mind and scales efficiently to 4K and 8K, where H.264's older toolset becomes less economical.^[1]

Both Are Codecs, Not Containers

H.264 and H.265 define how video is compressed, not how it is stored as a file. Streams encoded with either codec are placed inside a container such as MP4, MKV, or MOV, which adds audio, subtitles, and timing.^[2] The same codec can appear in different containers, and a container can hold either codec, which is why a file's extension does not indicate which codec it uses.

Licensing and Hardware

A practical difference is patent licensing. H.264 has a mature, widely-accepted licensing framework and near-universal hardware decode support.^[2] HEVC's licensing is administered across multiple patent pools, which has slowed its adoption on the open web and contributed to the development of royalty-free alternatives such as AV1.^[1] Hardware HEVC decoding is common on modern devices but less universal than H.264.

Compatibility and Applications

H.264 remains the most universally supported video codec, decodable by virtually every device and browser, making it the safest choice for broad distribution.^[2] H.265 is used where bandwidth or storage savings at high resolution justify its heavier processing and licensing, such as 4K streaming, modern broadcast, and recent mobile-device video capture.^[1]