H.264 is the dominant video compression standard of the early twenty-first century, used for everything from streaming video and video conferencing to Blu-ray discs and the recordings made by ordinary smartphones. It was developed jointly by the ITU-T Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group, working together as the Joint Video Team, and published in parallel by both bodies: as ITU-T Recommendation H.264 and as ISO/IEC 14496-10. The two texts are technically aligned, and the standard is known by several names, including H.264, MPEG-4 Part 10, and AVC (Advanced Video Coding).
The ITU catalogue record gives H.264 the title “Advanced video coding for generic audiovisual services,” with the original edition dating to 2003 and many subsequent editions extending it. The corresponding ISO record, ISO/IEC 14496-10, “Information technology - Coding of audio-visual objects - Part 10: Advanced Video Coding,” was first published in 2003 as well. The dual ITU/ISO publication continues the joint-development model that MPEG established with MPEG-2 and its ITU twin H.262.
H.264 follows the same broad block-based, motion-compensated, transform-coded approach as earlier MPEG video, but refines nearly every component to roughly double the compression efficiency of MPEG-2 at equivalent quality. Its innovations include variable block-size motion compensation, quarter-pixel motion vector precision, multiple reference frames, an integer transform that avoids the rounding mismatches of the classic floating-point DCT, an in-loop deblocking filter to reduce block artifacts, and advanced entropy coding schemes (CAVLC and the more efficient CABAC). The standard defines profiles and levels so that the same codec can serve constrained mobile decoders and high-end broadcast equipment alike.
Like its predecessors, H.264 is a lossy codec that exploits both spatial redundancy within a frame and temporal redundancy between frames, coding most pictures as predictions from reference frames plus compressed residuals. The standard specifies only the bitstream syntax and the decoding process, leaving encoder design open; this is what allows many competing encoders, from real-time hardware to slow high-quality software, to all produce compliant streams that any conforming decoder can play.
The combination of strong compression, broad hardware support, and a stable licensing framework made H.264 ubiquitous. It became the default codec for online video platforms, mobile capture and playback, and physical media, and it remains heavily used even as successors such as H.265/HEVC, VP9, and AV1 offer further efficiency gains. Its dual ITU-T and ISO/IEC standardization, and its reach into nearly every device that records or plays video, make H.264 one of the most successful and consequential standards in the history of digital media.