Resi Glossary

What is H.264 (AVC)?

H.264, formally known as Advanced Video Coding (AVC), is a video compression standard or codec that’s used by the majority of broadcasters to stream video. That’s because the codec is compatible with most devices, web browsers, HTML5 video players, and more. Video codecs like H 264 are crucial for reducing the file size of video content, and in turn, the bandwidth requirements for OTT streaming. While H.264 is a large improvement over MPEG-2 and other legacy codecs, H.265/HEVC is an even more efficient codec that is starting to gain adoption. 

H.264/AVC was created by several working groups known collectively as the Joint Video Team (JVT) in an effort to deliver higher quality streams at lower bitrates than previous standards. The H.264 standard was designed to be simple enough so that it could be implemented by numerous vendors across a variety of applications and devices. Apple, Microsoft, and Adobe have all developed versions of H.264 that are widely used, but there are differences in quality and performance amongst them.

Since it’s a proprietary codec, using H 264 for video streaming requires paying royalties. There’s a patent pool based on companies that contributed to the development of the standard, so royalties differ depending on use case. For example, there are fees for title-by-title, pay-per-view, subscription services, and more. There are no royalties, however, for video streams delivered for free over the Internet.

The standard doesn’t specify how exactly to encode videos, so encoder manufacturers have developed their own implementations based on H 264 profiles and levels. Many versions of H.264 use lossy compression algorithms, which means less important details are discarded during encoding to reduce the file size. In addition to multiple compression algorithms, H.264 is compatible with a range of container formats, from MPEG to MOV and Flash. 

With H264, profiles are used to specify the techniques and algorithms used to create a bitstream for various use cases. For example, the baseline profile is designed to support low-powered devices like smartphones and tablets while the high profile is the most widely used for broadcasts. H.264 also has levels that describe the maximum video resolution and data rate a specific device can support.

H.264 is a block-oriented codec, where video frames are divided into “macroblocks” or groups of pixels. When intermediate frames have macroblocks that appear the same as a reference frame, the information can be eliminated without significantly impacting the video’s perceivable quality. Even if a macroblock moves, H 264 uses macroblock motion vectors to save additional data. H.264 encoding also uses deblocking to smooth out colors and reduce pixelation during compression.

Resi’s hardware encoders support H.264 up to 1080p resolution out-of-the-box. Since encoding H 264 requires significant computing power, hardware encoders are ideal for live streaming using the codec when low latency is critical. In addition, Resi’s ProPresenter Stream allows broadcasters to encode in H.264 using existing hardware, which seamlessly integrates with Resi’s Live Stream Platform for a complete live streaming solution.

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