What is H.265 (HEVC)?

High Efficiency Video Coding (HEVC), also known as H.265, is a video codec or compression standard that’s steadily growing in adoption. In fact, H.265 is more efficient than H.264, which is its predecessor and currently the most widely used codec by broadcasters.

As video resolutions and quality expectations continue to increase, achieving greater compression efficiency is crucial for over-the-top (OTT) streaming. That’s because high-quality videos have larger file sizes and higher bitrates, which requires more bandwidth to stream to end-users. Compression can dramatically reduce the size of videos without impacting the perceived quality of the content.

The Joint Collaborative Team on Video Coding (JCT-VC) developed HEVC with the hope of achieving twice the compression efficiency as H.264. The concept for H.265 was largely an extension of H.264, but introduces numerous improvements during the encoding process. JCT-VC’s collaborative team of video encoding experts created the new standard to substantially reduce the file size and bitrate and in turn, the costs, associated with 4K and 8K video content.

More specifically, H.265 uses a technique known as motion compensation prediction. Similar to H.264 and other block-oriented codecs, H.265 divides video frames into macro-blocks or groups of pixels. If these macroblocks are the same over several frames, the information can be eliminated to save data. The codec can also predict the direction macroblocks are moving and encode this as a motion vector as well. Deblocking also helps to smooth out the colors between the macroblocks to reduce pixelation.

H.265 achieves greater efficiency than H.264 by supporting larger macroblocks up to 64 pixels and more precisely predicting motion vectors during encoding. This is possible due to the codec’s coding tree units (CTUs) approach for processing information. H.265 also has an improved deblocking filter and an additional filter to reduce artifacts at block edges called sample-adaptive offset filtering. 

While the initial version of H.265 was ratified in early 2013, adoption has been slow. The primary roadblock for adoption has been a complicated and expensive patenting scheme. H.265 is a proprietary codec like H.264, but there are several patent pools and the licensing fees are often much higher. This has prevented many browsers and device vendors from supporting the codec. 

Besides H.265, many broadcasters are turning to AV1 as a future codec. This is another high-efficiency codec that’s open-source and royalty-free. While AV1 might be even more efficient than H.265, the codec still hasn’t been adopted by some vendors. Google’s VP9 codec is another free alternative to H.265 that’s highly efficient and already compatible with Android, Chrome, and YouTube.

Resi’s server-grade hardware encoders support the H.265/HEVC codec up to 4K UHD resolution out-of-the-box. Since compression is resource-intensive, especially for high-efficiency codecs like H.264, hardware encoders are invaluable during live streams where low latency is critical. Resi’s ProPresenter Stream is a software encoder that enables broadcasters to encode live streams using their existing hardware as well. These hardware and software encodes seamlessly connect with Resi’s Live Stream Platform for a powerful end-to-end streaming solution.