H.264 vs H.265 vs AV1

Three generations of the same idea

All three codecs are block-based hybrid coders. They split each frame into blocks. Each block is predicted from nearby pixels (intra prediction) or from earlier and later frames (inter prediction with motion vectors). The leftover difference is transformed, quantised and entropy-coded. Efficiency gains come from doing each stage with more options: larger and more flexible block sizes, more prediction directions, better motion compensation and smarter entropy coding.

H.264, published jointly by ITU-T and ISO/IEC in 2003 as H.264 and MPEG-4 Part 10, uses fixed 16×16 macroblocks with sub-partitions down to 4×4. H.265, published in 2013 as H.265 and MPEG-H Part 2, replaces macroblocks with coding tree units of up to 64×64 pixels and adds 35 intra prediction modes. AV1 came from the Alliance for Open Media in 2018. It uses superblocks of up to 128×128 and adds tools such as compound prediction and film grain synthesis. It was designed from the start to be free of royalty claims from its contributors.

The codecs compared

Efficiency figures are the conventional rules of thumb quoted by the codec developers, not measurements from this site; real results vary widely with content and encoder settings.

H.264: the codec you can rely on

H.264's advantage is not technical. Every phone, laptop, games console, television and browser made in the last decade decodes it in dedicated chips. That means smooth playback at low power, even on hardware that would struggle with a software decoder. Profiles (Baseline, Main, High) and levels (such as 4.1 or 5.1) define what a decoder must handle. High profile at level 4.1 or 4.2 covers 1080p at normal frame rates and is the safe target.

x264 is the leading open-source encoder. It is mature enough that its "medium" preset gives good results quickly. Its slower presets close much of the gap to newer codecs at moderate resolutions. For uploads to a platform that will re-encode anyway, an H.264 source at a generous bitrate is the ideal start. The bitrate guide gives numbers by resolution.

H.265: more efficient, less certain

HEVC was built for 4K. Its larger coding tree units suit high resolutions, where large flat areas can be coded in a single block. Its Main 10 profile made 10-bit HDR mainstream, as the HDR guide explains. iPhones have recorded HEVC by default since iOS 11, and Apple platforms play it natively. Encoding costs several times the processor time of H.264 for the same content.

The complication is licensing. HEVC patents are held across several pools and independent holders, and the uncertainty about terms slowed browser adoption for years. Safari supports it. Chrome and Edge play HEVC when the operating system provides a hardware decoder. Firefox support depends on platform. So an HEVC MP4 is not a file you can hand to any web viewer with confidence. That is true even when it is exactly what your camera produced. If you need an H.264 copy, the free video converter makes MP4 files with H.264 video and AAC audio.

AV1: open, efficient, and still spreading

AV1 was created by a group that includes Google, Mozilla, Amazon, Netflix, Microsoft, Apple and others. Its specification is published under an open licence. Its patent policy grants royalty-free use of the technology members contributed. It matches or beats HEVC efficiency and adds tools that suit streaming. The best known is film grain synthesis. It strips grain before encoding and adds it back as an effect on decode, instead of spending bits describing noise.

Decoding support arrived in Chrome and Firefox in 2018-2019 and in hardware on newer GPUs, phones and televisions since. Apple added hardware AV1 decoding with its A17 Pro and M3 chips, which brought Safari playback with it on those devices. Software decoding with dav1d works well on capable laptops but drains batteries on older phones. So a file encoded only in AV1 still leaves out a real share of viewers. Encoding speed was the early complaint. SVT-AV1 has made it workable for batch pipelines, while libaom remains the reference.

Which codec for which job

Encoding realities worth knowing

• Efficiency claims assume a slow, careful encode. A fast HEVC or AV1 encode can be beaten by a slow x264 encode at the same bitrate.
• Hardware encoders (NVENC, Quick Sync, VideoToolbox) are quick but usually less efficient than software encoders at the same bitrate. They suit real-time capture more than final delivery.
• 10-bit encoding reduces banding in gradients, even for SDR content. HEVC and AV1 both handle it routinely. H.264 10-bit exists but has poor hardware support.
• A codec change always means a full decode and re-encode. That is why the transcoding guide matters even if you never run ffmpeg yourself.
• Whatever codec you upload, VideoBB delivers HLS renditions the viewer's device can play, so codec compatibility becomes the platform's problem rather than yours.